Ramsden, JESSE

Ramsden, JESSE, a mathematical instrument-maker, was born at Salterhebble, near Halifax in Yorkshire, in 1735, and began life as a cloth-worker. About 1755 he moved to London, and shortly afterwards began to work as an engraver. His skill recommended him to the mathematical instrument-makers, the daughter of one of whom, Dollond, he married. Being of an inventive turn, he spent his best efforts in effecting improvements in the sextant, theodolite, equatorial, barometer, micrometer, mural quadrant, and the like. He so improved the sextant that its range of error was diminished from 5 minutes to 30 seconds. He made the theodolite for the ordnance survey of England. He devised the mural circle, and made the first for Palermo and Dublin. He spent several years over an instrument for graduating mathematical instruments (see GRADUATION), and published an account of it as Description of an Engine for Dividing Mathematical Instruments (1777). For this the Commissioners of Longitude awarded him £615. He was elected a Fellow of the Royal Society in 1786, and was voted the Copley medal in 1795. He died at Brighton on 5th November 1800. Descriptions of some of his improved instruments will be found in Phil. Trans. (1779 and 1783). See Life by Lalande in Journal des Sçavans (1788).