Deslandres, Henri Alexandre 1853-1948
French spectroscopist and astronomer

Born in Paris, he was educated there at the �cole Polytechnique, where he worked in laboratory spectroscopy with Marie-Alfred Cornu (1841-1902). He studied the band spectra of diatomic molecules, and found a formula for their frequencies, known as Deslandres' law (1885). In 1889 he took up astronomical spectroscopy on joining the Paris Observatory, but his greatest successes were in the field of solar spectroscopy, inventing the velocity spectrograph (1891), an instrument which allowed photographs of successive strips of the Sun to be taken in the light of a particular spectrum line. In 1897 Deslandres moved to the astrophysical observatory at Meudon, of which he became director in 1908. He was elected to the French Academy of Sciences in 1901 and was awarded the gold medal of the Royal Astronomical Society in 1913.