Proportional compasses

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This pair of proportional compasses were made around 1800, probably by Thomas Jones, a scientific instrument maker based at Charing Cross in London. The proportional compasses are dividers capable of several operations.

The compasses can move about on a sliding pivot, altering the ratio between the long points at one end and the short ones at the other. This side has scales allowing the area and volumes of two-dimensional diagrams to be calculated.

Proportional compasses were used in practical mathematics, particularly in skilled trades such as surveying and navigation, to calculate dimensions when transferring drawings either when enlarging or reducing.

Record details

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• Online ID: 000-100-102-665-C
• Image Rights Holder: National Museums Scotland
• Project: National Museums Scotland
  Project description   View all records in project
• Ref: National Museums Scotland  T.1911.97
• Date: Around 1800
  c. 1800
  
• Material: Inscription: R 60 [Admiralty mark]
  Specimen / drawing instrument / compasses, proportional
  
• Dimensions: 8.50" L
  
• What: Specimen / drawing instrument / compasses, proportional
  
• Subject: 19. MATHEMATICS (Departmental Classification)
  
• Who: Admiralty (Owner)
  Thomas Jones, 62 Charing Cross, London (Instrument maker)
  
• Where: England, London
  
• Event:
• Description: One of a collection of surveying, nautical, astronomical, meteorological and drawing instruments - proportional compasses, marked, made by Thomas Jones of London, c. 1800
  
• References:
  • Hambly, Maya, Drawing Instruments 1580-1980. London: 1988, pp 126-8 
• Translations:
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