Theodolite

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A theodolite is a surveying instrument for measuring horizontal and vertical angles. This brass example was made around 1770, probably by Jesse Ramsden, a scientific instrument maker based in London.

The theodolite's telescope is supported by two brackets above an 180 degree arc which is adjusted against the vernier scale by rack-and-pinion. This is mounted over a horizontal circle which contains a central compass, engraved 'Ramsden, London'. The whole is on a raised column above four levelling screws.

Jesse Ramsden (1735-1800) is credited by George Adams with the innovation of permanent double 'A' frames on the horizontal circle of the theodolite. This is clearly a slightly less mechanically-stable precursor to that design.

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• Online ID: 000-100-104-299-C
• Image Rights Holder: National Museums Scotland
• Project: National Museums Scotland
  Project description   View all records in project
• Ref: National Museums Scotland  T.1987.132
• Date: Around 1770
  c. 1770
  
• Material: Theodolite, simple
  
• Dimensions:
• What: Theodolite, simple
  
• Subject:
• Who: J. Ramsden, London (Maker)
  
• Where: England, London
  
• Event:
• Description: Simple theodolite by J. Ramsden of London, c. 1770
  
• References:
  • For Ramsden, see Clifton, Gloria, Directory of British Scientific Instrument Makers 1550-1851. London: 1995, pp 227-8 
  • For the development of the theodolite, see Bennett, J.A., The Divided Circle: A history of instruments for astronomy, navigation and surveying. Oxford: 1987, pp 145-9 
  • Nuttall, R. H., The Arthur Frank Loan Collection: Early Scientific Instruments. Glasgow: 1973, item 623 
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