Lassell, WILLIAM

Lassell, WILLIAM, astronomer, born at Bolton, in Lancashire, on 18th June 1799, 'belongs to that class of observers who have created their own instrumental means.' He built himself a private observatory at Starfield, near Liverpool, about 1820, and observed there down to 1861. There, too, he constructed and mounted equatorially reflecting telescopes of 9 inches aperture and 2 feet aperture successively. The speculum of the latter was polished by means of a machine of Lassell's own invention. With this same telescope he discovered the satellite of Neptune (1847); the eighth satellite of Saturn (1848), simultaneously with Prof. Bond of Harvard; and two new satellites of Uranus (1851). In 1861 he went out to Malta, and there set up a reflecting telescope of 4 feet aperture and 37 feet focal length, mounted equatorially; with this he made observations until 1865, chiefly of nebulae and the satellites he had discovered. After his return to England he transferred his observatory to near Maidenhead. There he died on 5th October 1880. See Memoirs of Astron. Soc., vol. xxxvi., for his work in Malta, and Trans. Roy. Soc. (1874) for a description of his polishing-machine.