Hadley, JOHN, an English mathematician, the inventor of Hadley's quadrant (see SEXTANT) and of a reflecting telescope (1723). The honour of having invented the sextant is claimed for Hadley, Godfrey, and Newton. Each seems, however, to have made his own discovery independently. Hadley described his instrument, which he called an 'octant,' to the Royal Society on 13th May 1731. He contributed several papers to the Transactions of the society from 1717 onwards. Born in 1682, he died 14th February 1744.
Hadley, JOHN
Chambers's Encyclopaedia, Volume 5: Friday to Humanitarians, p. 496
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