Vogel’s classification of spectra is generally adopted by astronomers, although others have been proposed by Lockyer and by _Edward Charles Pickering_ (born 1846), director of the Harvard Observatory. Lockyer’s classification was designed to fit in with his “meteoritic hypothesis,” discussed in the chapter on Celestial Evolution. The stars were divided by Lockyer into seven groups, according to his views of their temperature, rising through gaseous stars, red stars of Secchi’s third type, and a division of solar stars to the Sirian type, and falling through a second division of the solar type to red stars of Secchi’s fourth type. The first spectroscopic star-catalogue was published in 1883 by Vogel, assisted by _Gustav Müller_ (born 1851), a son-in-law of Spörer. The catalogue contained details of 4051 stars to the seventh magnitude, and more than half of these proved to be of Secchi’s first type. Vogel’s work was completed in different latitudes by Dunér at Upsala, and by _Nicolaus Thege von Konkoly_ (born 1842) at O’Gyalla in Hungary. The famous ‘Draper Catalogue’ ranks as the greatest catalogue of stellar spectra. It was undertaken at Harvard Observatory by E. C. Pickering, in the form of a memorial to Henry Draper, the successful spectroscopist. Commenced in 1886, and published in 1890, it contains photographs of the spectra of no fewer than 10,351 stars, down to the eighth magnitude. Pickering subdivided Secchi’s types into various classes, the first or Sirian into four classes, the second into eight, while the third and fourth types each constitute a separate class. Pickering designated his classes by the capital letters of the alphabet. Much useful work has been done also in the analysis of the various spectra. Julius Scheiner, now “chief observer” at Potsdam Astrophysical Observatory, has, since 1890, done much valuable work in this direction. Special attention was devoted to the spectrum of Capella, 490 lines in the spectrum of which were measured by Scheiner. In his own words, “he believes a complete proof of the absolute agreement between its spectrum and that of the Sun to be thereby furnished.” Other stars of the Sirian and solar classes were exhaustively studied by Scheiner. The study of the exact brilliance of the stars was a branch of research long neglected, yet it is of much importance in astronomy, for it is only through exact measurement of stellar brilliance that stellar variation can be detected. Herschel commenced the study, which was continued by his son at the Cape, but it is only within the last twenty years that stellar photometry has become a recognised branch of astronomy; and the credit of this is due to the energy and zeal of the great American observer, Edward Charles Pickering.