( 460 ) 



the star's light, in such a way that thej correspond to an approach 

 befoi-e the principal minimum and to a recession after that time. 

 From these observations he derived a circular orbit for that com- 

 ponent which eclipses the other at the time of this minimum. The 

 investigation of the Potsdam spectographs equally led Prof. Vogel ') 

 to the conclusion that the displacement of the lines can hardly be 

 explained otherwise than as a consequence of the motion of different 

 bodies having unequal spectra. He does not succeed however in 

 determining the position of the lines with sufficient accuracy. He 

 thinks that the photometric data would lead to the assumption of 

 two bodies of unequal luminosity moving either in a fairly circular 

 orbit or in an ellipse having its major axis in the visual line. On the 

 other hand the spectroscopic investigations would lead to the assump- 

 tion of two bodies, one showing a spectrum with luminous, the 

 other a spectrum with absorption-lines, which would describe very 

 excentric orbits the major axes of which would make a considerable 

 angle with the visual line. It would be impossible, in his opinion, to 

 satisfy the tw^o phenomena at the same time. In 1896 Dr. Myers ') 

 subjected Argelander's lightcurve ("vera" pro 1850) to an elaborate 

 theoretical investigation. His result is that the whole curve of the 

 lightvariation is represented satisfactorilj'- by assuming two elongated 

 revolution ellipsoids the major axes of which are in each other's 

 prolongation, circulating around each other in nearly circular orbits. 



The next year Belopolsky found the duplicity confirmed '). This 

 time it was the displacements of the dark JT^-line (P. := 448.2 nn), 

 which enabled him to derive a slightly excentric orbit for the second 

 component viz. of that component which is eclipsed during the 

 principal minimum. Father W. Sidgreaves, in his latest spectrographic 

 investigation of /i Lyrae '') arrives at the same result as Prof. Vogel : 

 rather considerably excentric orbit, the ma,jor axis of which makes 

 a great angle with the visual line. 



In conformity with what had already been suggested before by 



1) Ueber das Spectrum von j3 Lyrae. Von H. G. Vogel. Sitzungsberichte der 

 K. Preussischen Ak. der Wiss zu Berlin. 8 Februar 1894. 



2) Untersuchungen iiber den Liclitwechsel des Slernes .- Lyrae. luaugiiraldisser- 

 tation . . . von G. W Myers^ Miinchen 1896. — The system of /3 Lyrae. id. The 

 Astroph. Journ. Vol. VII N". 1. 



^) Recherches nouvelles dii spectre de k Lyrae, par A. Belopolsky. Memorie 

 della Societa degli SpetU'osc. It. vol. XXVI, 1897. — New Investigations of the 

 Spectrum of (3 Lyrae, id Astroph. J. Vol. VI N». 4. 



*) A spectrographic Study of ^ Lyrae. By Rev. Walter Sidgreaves S. J. Monthly 

 Notices of R. A. S., Jan. 1904. 



