born Oct. 14, 1788, Dublin, Ire.
died June 26, 1883, East Sheen, Surrey, Eng.
British astronomer and geodesist.
He accompanied the expeditions of John Ross (1818) and William Parry (1819) in search of the Northwest Passage. In 1821 he began experiments to determine the Earth's shape more precisely by observing the motion of a pendulum. He thereafter devoted most of his efforts to researches on terrestrial magnetism, overseeing the establishment of magnetic observatories throughout the world. In 1852 he discovered that the periodic variation of sunspots is correlated with certain changes in magnetic disturbances. He was president of London's Royal Society (1861–71). Knighted in 1869, he was promoted to the rank of general in 1870.