Museum of the History of Science logo

<< First | < Previous | Next > | Last >>

37 Early Brass Sextant by Jesse Ramsden

image of Early Brass Sextant by Jesse Ramsden

image of Early Brass Sextant by Jesse Ramsden

The antique dealer from whom I bought this instrument many years ago, intrigued me with a story about its maker Jesse Ramsden. He said that Ramsden was very particular and fastidious about his instruments and took fifteen years to make a large telescope for an observatory. He had an audience with the King who thanked him for arriving on time and on the correct day, except the appointment was for the previous year.

Private Collection, W. Midlands, U.K.

Jesse Ramsden (1735-1800) had the justifiable reputation, in his own lifetime, of being London’s finest scientific instrument maker. He hailed from Yorkshire where he was apprenticed into the textile industry, but in 1758 he apprenticed himself to the London scientific instrument maker Mark Burton for four years. He opened his first shop about 1763 and two years later he began to develop a machine that would be able to accurately mark the divisions on instruments such as sextants, completing his first dividing machine in 1768.

A close inspection of the divisions of the scale on this instrument show a number of ‘mistakes’ which would not have occurred had he used his machine, which he claimed his staff and his wife could use. By 1770, Ramsden had also improved the frame, making sextants with a T-bar construction and it is inconceivable that Ramsden would choose to divide an instrument by hand, a time-consuming procedure, when his machine could do the same work more quickly.

English, c.1765

See: Bulletin of the Scientific Instrument Society (forthcoming), where close-up pictures of the scale will be published.
A. McConnell, Jesse Ramsden (1735-1800) London’s Leading Scientific Instrument Maker, Aldershot, 2007, pp. 12-17, 33, 41


Objects lent by Anonymous Lender II, West Midlands, UK:

04. Beam Compass, by George Adams, London, 1757-60

13. Waywiser, by George Adams jr, London, between 1784 and 1796

35. Silver Engine-Turned Box Sextant, by Troughton, London, c. 1810

42. Hydrostatic Balance, by George Adams, London, c. 1760

50. Three Early Forms of Electro-Magnetic Demonstration Motor, English, c. 1835-40

Back to top