Deslandres, Henri

Born July 24, 1853, in Paris; died there Jan. 15, 1948. French astronomer. Member of the Paris Academy of Sciences (1902) and the Bureau of Longitudes; director of the Meudon Observatory near Paris.

In 1891, Deslandres invented the velocity recorder and spectroheliograph (independently of the American astronomer G. Hale). He used this instrument at the Meudon Observatory to make daily photographs of the chromosphere of the entire solar disk. Deslandres discovered the laws governing the arrangement of absorption bands in the spectra of gases and, with A. H. Becquerel, investigated the action of the magnetic field on the positions of spectral lines. He also measured the velocities of rotation of the different parts of Saturn’s rings and obtained numerous photographs of the large planets and planetary nebulas.