Graphometer

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A graphometer is a surveying instrument used for measuring angles. This brass example (pictured here with its leather case) was made in 1774, probably by Louis-Pierre-Florimond Lennel, a scientific instrument maker based in Paris.

The large graphometer, typical of French survey instruments of the period, has a telescopic sight, attached to a rotatable alidade. It consists of a pierced semicircular plate, carrying at its centre a silvered compass, contained in a glazed box suspended below the plate. A second, fixed, telescope is mounted below the plate.

The instrument may well have been used in the French National Survey as its leather case carries the official fleur-de-lys stamp. This survey took place throughout the 18th century, but never received sufficient state backing: triangulation work began in 1747, with funding withdrawn in 1756. By 1784 only Brittany was unsurveyed, and this was not completed until well after the French Revolution, in 1818.

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• Online ID: 000-100-104-247-C
• Image Rights Holder: National Museums Scotland
• Project: National Museums Scotland
  Project description   View all records in project
• Ref: National Museums Scotland  T.1973.71
• Date: 1774
  
• Material: Leather case
  Graphometer / case
  
• Dimensions:
• What: Graphometer / case
  
• Subject: 5. CARTOGRAPHY, Surveying (Departmental Classification)
  
• Who: E. Lennel, Paris (Maker)
  
• Where: France, Paris
  
• Event:
• Description: Graphometer, in a leather case, signed by E. Lennel of Paris, 1774
  
• References:
  • Bennett, J.A. The Divided Circle: A history of instruments for astronomy, navigation and surveying. Oxford: 1987. p 87 
  • For Lennel, see Daumas, M. Scientific Instruments of the 17th and 18th Centuries and their Makers. London: 1972, pp 262 & 332, and Augarde, Jean-Dominique, 'La fabrication des instruments scientifiques du XVIIIe siecle et la corporation des fondeurs' in B 
  • Wynter, H. & Turner, A., Scientific Instruments. London: 1973, p 158 
• Translations:
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