Repeating circle (2 of 2)

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A repeating circle is similar to the reflecting circle, in which a series of observations are 'repeated', so that the error between readings is increasingly narrowed. This portable example, intended for astronomical readings possibly on a voyage of exploration, was made around 1800, probably by Thomas Jones (1775-1852), a scientific instrument maker based in London's Charing Cross.

This instrument was derived from one described by Edward Troughton in 1822. Thomas Jones had been apprenticed to Troughton. The instrument is inscribed below the scale 'I.2/ Thomas Jones, 62 Charing Cross London.' It has an Admiralty mark 'C 1'.

Thomas Jones held the instruments made for the Hydrographic Office from early 1826, but in February 1828 these were returned to that department and marked with various letters. Unfortunately, it has not been possible to identify which instruments went on particular voyages of discovery.

Record details

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• Online ID: 000-180-001-165-C
• Image Rights Holder: National Museums Scotland
• Project: National Museums Scotland Part 2
  Project description   View all records in project
• Ref: National Museums Scotland  T.1910.89
• Date: Around 1800
  c. 1800
  
• Material: Glass. Inscription: C 1 [Admiralty mark]
  Specimen / astronomical instrument / altazimuth instrument / box
  
• Dimensions: 15.75" L; 1.50" D
  
• What: Specimen / astronomical instrument / altazimuth instrument / box
  
• Subject: 3. ASTRONOMY, Transits (Departmental Classification)
  
• Who: Admiralty (Owner)
  Thomas Jones, 13 Panton Street, Haymarket, London (Instrument maker)
  
• Where: England, London
  
• Event:
• Description: One of a group of nautical, astronomical and drawing instruments - an altazimuth instrument with stand, Admiralty mark "C 1", in a box, made by Thomas Jones, Haymarket, London, c. 1800
  
• References:
  • Edinburgh Encyclopaedia 1830 Vol VI pp 498-514 and plate CXLVII. Also, Edward Troughton, 'An Account of the Repeating Circle...' Philosophical Magazine, LX (1822), pp 8-18 and 102-108 
  • For the marking of instruments for the Hydrographic Office, see Stimson, A.N., 'Some Board of Longitude Instruments in the Nineteenth Century' in De Clercq, P.R., Nineteenth Century Scientific Instruments and their Makers, Amsterdam and Leiden, 1985, App 
  • J.A. Bennett, The Divided Circle: a History of Instruments for Astronomy, Navigation and Surveying, Oxford, 1987, p 167 
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