1890.] Rayefs Bright-Line Stars in Cygnus. 39 



band of the Bunsen flame ; but, further, the want of accordance of its 

 general characters is so great as to make the view that its origin is 

 carbon very improbable. This improbability is very greatly in- 

 creased when we find, as will be shown presently, that no traces 

 whatever of the very bright beginnings of the more brilliant gresn 

 and orange bands could be detected by iis in any of the stars. 

 Further, Professor E.G. Pickering has kindly sent to us an account of 

 his photographs of this star, which, though they show the hydrogen 

 line at X 43-4, do not exhibit any brightness at the positions of the 

 indigo hydrocarbon bands, beginning near 4312, and X 4382. 



This star, however, can scarcely be taken by itself; in the case 

 of the other two stars, in the spectra of which, according to Vogel's, 

 Copeland's, and our own observations, the brightest part of the blue 

 band is from X 464 to X 465, but nearer X 465, quite outside the 

 ordinary visible limit of the carbon band, the evidence seems very 

 strong indeed that the band does not owe its origin to carbon. 



We satisfied ourselves that when the spectrum of the star is 

 examined under the dispersion of spectroscope B, none of the 

 brighter parts of its spectrum fell at, or very near, the green, 

 orange, and indigo flutings of the hydrocarbon flame spectrum ; at 

 these positions we were unable to detect any sensible brightening of 

 the star's spectrum. Professor Copeland's measure of the blue band 

 in 1884 was X 469'5. 



No. 4013. Vogel does not give measures of the beginning and the 

 ending of the band in this star, but only of the brightest part : 

 " Hellste Stelle, nahezu Mitte, einer breiten verwaschenen Bande, 

 X. 464." He gives, however, a diagram of the spectrum in which the 

 bright blue band is represented as substantially coincident in position 

 and in general character with that in the spectrum of No. 3956. 



Our observations agree substantially with those of Vogel, but they 

 make the band to consist of two parts a very bright part, from 

 about X 466 to X 464, but brightest near X 465, and a very faint 

 band, apparently detached from the bright one from about X 4685 to 

 about X 4705. This faint band is brightest near where it ends rather 

 abruptly at the more refrangible end. The very bright band has not 

 the character of a fluting, nor is it broken up into maxima widely 

 separated like those of the Bunsen flame band, but appears to be a 

 group of bright lines. The lines were only glimpsed at moments ; it 

 is therefore difficult to make a drawing which truly represents the 

 character of the band as seen in our instruments. The band, which 

 is shown at No. 5 of the diagram, is left unfinished at the more 

 refrangible end, as we were not certain how far we ought to consider 

 it to extend. 



In this star (as we shall show to be the case in No. 3956 also), the 



