A mathematical instrument-maker, born in Spitalfields, London, of Dutch descent; began life as a silk-weaver; made good use of his leisure hours in studies bearing mainly on physics; went into partnership with his son, who was an optician; made a study of the telescope, suggested improvements which commended themselves to the Royal Society, and in especial how, by means of a combination of lenses, to get rid of the coloured fringe in the image (1706-1761).