Ramsden Sextant

[Text discription below]

40022

A Fine Sextant by Jesse Ramsden:

London ca. 1785.  SN 1277.  Signed Ramsden London.  This was Jesse Ramsden (b 1735 - w 1762 - d 1800), a leading Scientific Instrument Manufacturer working in London during the mid 18th century (1,2).  His workshops were recorded in the Strand and in Haymarket, London as well as at two different locations in Piccadilly.  Ramsden produced a wide variety of optical, navagational and mathematical instruments.  He is best known for the invention of the dividing engine (See picture.).  This instrument produced scales on rules, sectors, compasses, sextants, and measuring instruments of all sorts, with incredible accuracy.  The machine itself became known as "Ramsden's Dividing Engine," and is still the topic of many scholarly theses today (2,3).  The accuracy of Ramsden's instruments was so noteworthy, that he developed a reputation as having the most high precision instruments available, and hence they commanded premium prices in his time.  It is well known that Captain Cook used a "highly praised" sextant,  produced by Ramsden, during his Pacific voyages in 1772 and 1776. 

The present instrument is known as a Bridge Frame Sextant.   It differs from a normal sextant by the additional framing over the top.  It is 10 in high and has a radius of 7 in.  This would have been a very advanced instrument for its time, possessing an additional frame (The Bridge frame.) as well as a high precision scale engraved on platinium, that was produced on Ramsden's own dividing engine.

Condition:

Fine quality and high precision.  Well preserved.  No damage or replacement parts.  Fully functional.  An 18th century sextant, in original, as found condition, by a highly recognized English scientific instrument maker.  Complete with case, original key, and accessories.

Bibliography:

1.  Clifton, Gloria (1995) Directory of British Scientific Instrument Makers 1550-1851. ISBN [0 302 000634 6]  p. 227.

2.  McConnell, Anita (2007) Jesse Ramsden (1735-1800) London's Leading Scientific Instrument Maker.  ISBN [9780754661368].

3.  Online resources: 

a.)  [www.en.wikipedia.org/wiki/Jesse_Ramsden].

4.  Jesse Ramsden's trade card is reproduced here, for use in this forum, by permission from the Science Museum London.

5.  The picture of Jesse Ramsden is reproduced here, by permission from The Royal Society.  The portrait was painted by Robert Home in ca. 1777, and gifted to the Royal Society by Sir James Everard Home on JUN 14, 1850.  ©The Royal Society.