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Jesse Ramsden British, 1735-1800, circa 1793


Signed "Ramsden London" on the cross-bar and numbered 1147 on the reverse side. The brass "T" frame quintant, with inset silver scale that reads from 2 to 147 degrees with a 5-1/8" radius arm with tangent screw and clamp, with handle, three brass feet, and an assortment of lenses, eye-pieces and other fittings all contained in the original mahogany box. An old label in the box instructs "To correct error of division in centering add 1' every 10 degrees." The fine use of brass, when many other instruments were still being made in ebony, and the quality of workmanship mark this instrument as the work of a master craftsman and inventor.
Instrument: Height 6". Width 7". The box, Height 2.75" Length 6.5". Width 7.75".

  • Provenance:
    Sotheby's, London, Frank Collection of Scientific Instruments, 1986.
    The Kelton Collection of Marine Art & Artifacts.

    This jewel-like brass 'T' Frame Quintant, made in about 1793 based on records at the National Maritime Museum, Greenwich which show a later serial number (1415) was manufactured in 1799, and the earlier number (842) was 1785. Even the finest instrument makers were having difficulty at this time in making totally perfect instruments.

    Jesse Ramsden (1735-1800) was one of the premier instrument makers of his time. His instruments were carried by Captain Cook and Humbolt on their scientific voyages of discovery. In the course of his apprenticeship, Ramsden worked for John Bird (1709-1776), the maker of the first sextant. in 1762 he opened his own workshop in the Haymarket, and in 1766 married the sister of Peter Dollond, another famous instrument maker. As part of her dowry, Ramsden received a share in the achromatic objective lens patent owned by its inventor, his father-in-law, John Dollond (1706-1761). In 1775 he developed an improved dividing machine for marking the gradations on instrument indexes. The English board of Longitude awarded Ramsden a substantial prize on the condition he publish a description of the new engine (done in 1777), instruct up to ten instrument makers in its use, and permit other instrument makers to use it for a fee. The original engine is now preserved in the U.S. National Museum in Washington D.C.
  • Exhibited:
    Pacific Asia Museum at U.S.C., Trade and Treasure Exhibition, 1987.

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