Hadley, John (1682-1744), inventor of the reflecting quadrant, was from an early age a proficient in mechanics, and took out a patent for a water-wheel. In 1717 he became a fellow of the Royal Society, and was afterwards Vice-President. In 1719 he made the first serviceable reflecting telescope, and in 1730 the idea of his great invention seems to have occurred to him at the same time as it did to Newton. Hadley was intimate with Sir Hans Slonne, near whom he had a house in Bloomsbury. His brother George (1685-1760) was the first to formulate the now accepted theory of the trade-winds.