DOLLOND, JOHN 0706-1760, F.R.S. (1761), English optician, was the son of a Huguenot refugee, a silk-weaver at Spitalfields, London, where he was born on June o, 17°6. He followed his father's trade, but found time to acquire a knowledge of Latin, Greek, mathematics, physics, anatomy and other sub jects. In 1752 he abandoned silk-weaving and joined his eldest son, Peter Dollond (1730-182o), who in 175o had started in business as a maker of optical instruments. His reputation grew rapidly, and in 1761 he was appointed optician to the king. In 1758 he published an "Account of some experiments concerning the different refrangibility of light" (Phil. Trans., 1758), describ ing the experiments that led him to the discovery of a means of constructing achromatic lenses by the combination of crown and flint glasses. Following the suggestion of Leonard Euler and the experiments of Samuel Klingenstjerna (1698-1765) Dollond commenced a series of tests on achromatism. Early in 1757 he succeeded in producing refraction without colour by the aid of glass and water lenses, and a few months later he obtained the same result by a combination of glasses of different refrangi bilities (see TELESCOPE). Dollond also published two papers on apparatus for measuring small angles (Phil. Trans., 1753, I754)• He died in London on Nov. 3o, 1761.