176 A CENTURY'S PROGRESS IN ASTRONOMY. 



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. 



Born in Boston in 1846, Edward Charles 

 Pickering was appointed in 1865 Instructor of 



