1890.] On Wolf and Rayefs Bright-Line Stars in Cygnus. 33 



IV. " On Wolf and Ra jet's Bright-Line Stars in Cygmis." By 

 WILLIAM HUGGINS, D.C.L., LL.D., F.R.S., and Mrs. HUGGINS. 

 Received November 25. 1890. 



In 1867 MM. Wolf and Rayet discovered at the Paris Observatory 

 three small stars in Cygnus, which in the spectroscope showed several 

 bright lines upon a continuous spectrum.* All three stars have a 

 very bright band in the blue part of the spectrum. 



These stars aro : 



B.D. +35, No. 4001. 

 B.D. +35, No. 4013. 

 B.D. +36, No. 3956. 



Their spectra were described in 1873, by Vogel, whose observations 

 agree substantially with the original description given by Wolf and 

 Rayet.f A more complete account of their spectra was given by 

 Vogel in 1883, from observations at Vienna with the 27-inch 

 refractor made by Sir Howard Grrubb. J 



Vogel's measures of the bright blue band place it in the star 

 No. 3956 at from X 468 to X- 461, with a maximum at X 464; in the 

 star No. 4013 with a maximum at the same place in the spectrum; 

 while the corresponding blue band in the star No. 4001 has a con- 

 siderably less refrangible position, commencing at X 470, reaching a 

 maximum at X 468, and ending about X 465. 



These later measures, though they differ from his earlier ones, in 

 ,so far as they show that the blue band has not an identical position 

 iu all three stars, nevertheless support substantially his earlier obser- 

 vations, which Vogel considered to show, contrary to the statements 

 of Secchi, that the bright lines, including the blue band, were not 

 due to carbon. 



In the diagram, Nos. 1, 2, and 3 show the positions of the bright 

 bands in the three stars, according to Vogel's measures, relatively to 

 the blue band of the hydrocarbon flame. 



Vogel's measures are : 



End of 

 the band. 



X465 

 X461 



* ' Comptes Rendus,' vol. 65, 1867, p. 292. 

 t ' Berichte K. Sachs. G-es. der Wiss.,' Dec., 1873, p. 556. 

 J * Publicationen Astrophys. Observ. Potsdam,' vol. 4, No. 14, pp. 17 21. 

 VOL. XLIX. ' D 



