CHAPTER X. 169

THE LIGHT OF THE STARS. Work of Fraunhofer and Donati—Life and work of Secchi—His types of spectra—Life and work of Huggins—Photography of spectra—Life and work of Vogel—His classification of spectra—Work of Dunér—Of Pickering—Spectroscopic catalogues—Analysis of spectra—Stellar photometry—Life and work of E. C. Pickering—Variable stars—Work of Goodricke—Of Argelander, Schmidt, Heis, Schönfeld—Studies of Dunér—Of Gore—Photographic discoveries—Classification—Algol variables: their explanation—Explanation of other variables—η Argus—Temporary stars—Of 1848—Of 1866—Of 1876—Of 1885—Of 1892—Photographic discoveries—Nova Persei, 1901—New star of 1903—Theories of temporary stars