Fraunhofer.

Fraunhofer. JOSEPH VON, German optician, was born at Straubing, in Bavaria, 6th March 1787. In 1799 he was apprenticed to a glass-cutter and polisher in Munich, and in 1807 he was employed to found an optical institute at Benediktbeuern, of which he became sole manager in 1818, and which a year later was removed to Munich. There he became a member of the Academy of Sciences in 1823, and was also appointed professor and conservator of the physical cabinet of the same institution. He died 7th June 1826. His more important inventions and improvements in optical instruments include a machine for polishing parabolic surfaces, another for polishing lenses and mirrors without altering their curvature, a spherometer, a heliometer, a micrometer, an achromatic microscope, and the great parallactic telescope at Dorpat. But his name has been rendered most celebrated by the improvements he effected in the quality of telescopic prisms and in the mechanism for manipulating telescopes of large size, and above all by his discovery of the dark lines in the sun's spectrum (see SPECTRUM), which bear the name of Fraunhofer's lines.