HARTMANN, JOHANNES FRANZ (1865-1936), Ger man astronomer, was born at Erfurt on Jan. II, 1865. From 1886 91 he studied mathematics in Tubingen, Berlin and Leipzig. In 1891 he was appointed assistant in Leipzig observatory. In 1909 he became professor of astronomy and director of the observatory in Gottingen, and in 192I director of the university observatory at La Plata, Argentine. He worked on spectrographs and dis persion-curves and wrote numerous papers on his spectral observations. He edited the volume on astronomy in the series Die Kultur der Gegenwart (1921) . Hartmann invented the micro photometer (1899), and the spectrocomparator (19o4). With Plaskett and Otto Struve, he discovered and investigated the calcium clouds in space.