STELLAR SYSTEMS AND NEBULAE. 205 



the Lowell Observatory, and by Edwin Brant 

 Frost (born 1866), now director of the Yerkes 

 Observatory, and his assistant, Walter Adams. 

 In 1894 Belopolsky discovered the duplicity of 

 several variable stars, and in 1896 that of Castor, 

 in Gemini. Late in 1896 Campbell undertook a 

 systematic investigation of radial motions, and 

 has since discovered about sixty spectroscopic 

 binaries, among them, in 1899, the Pole Star, 

 and in 1900 Capella. The latter discovery was 

 made independently by Hugh Frank Newall 

 (born 1857) at Cambridge, in England. It was 

 found by Campbell that the revolution of the 

 stars round their centre of gravity is performed 

 in 104 days ; and it soon became apparent 

 that, owing to the large size of the orbit, the 

 duplicity of Capella might be observed tele- 

 scopically. At Greenwich the star was seen 

 to be elongated, but at the Lick Observatory 

 it was seen persistently single. 



Campbell finds that of 285 stars observed by 

 him, more than one in nine is a spectroscopic 

 binary. He concludes that at least one star in 

 five or six will be found to be spectroscopically 

 double, and considers that " the proven existence 

 of so large a number of stellar systems, differing 

 so widely in structure from the Solar System, 

 gives rise to a suspicion at least that our 



