NEW STAR IN THE CONSTELLATION SWAN. 65 



probably to be the result of an incandescent vapor or gas." Here it 

 will be seen, is a first point of resemblance to the variable star of 

 Corona Borealis. 



A second study, made by Cornu on December 4th, enabled him to 

 define the bright lines of the spectrum. Three of them are the lines 

 C, F, and 434 of hydrogen ; a fourth line seemed to correspond to the 

 line D of sodium; another to the characteristic line b of magnesium. 

 Finally, two lines with the wave-lengths 531 and 451 seem to coincide, 

 the one with the famous line 1,474 (Kirchhoff's scale) observed in 

 the solar corona during eclipse, the other with a line of the chromo- 

 sphere. These results possess so high an interest that we will here 

 transcribe a portion of the text of M. Cornu's note : 



"The spectrum of this star," he writes, "consists of a certain number of 

 detached bright lines on a sort of luminous ground, almost entirely interrupted 

 between the green and the indigo, so that the spectrum appears as though made 

 up of a number of separate parts. In order to study it quaUtatively, I adopted a 

 spectroscopic eye-piece of special construction, which utiUzes most of the light, 

 and allows the observer to vary its concentration. In measuring I used a direct- 

 vision Duboscq spectroscope. I observed only bright lines ; the dark lines, if 

 any there are, must be very minute, and escaped my observation, owing to the 

 faintness of the star's light." 



In this respect the spectrum of the star in the Swan differs from 

 that of the star T of Corona Borealis, as may be seen from the figure 

 here copied from Huggins, 



We omit the details of the measurements of the positions of the 

 lines, and pass to the results, which are stated in the following table. 

 The bright lines, ranged in the order of their brightness, a, ^, y, /3, ^, 

 ?/, 0, e, are eight in number, and their wave-lengths are here given 

 in millionths of a millimetre : 



From this table it is seen that there is almost perfect coincidence 

 as regards the lines-a, ?/, and e, with three hydrogen-lines ; as regards 

 i3, with the line h of magnesium ; as regards 6, with the line of sodium, 

 or, perhaps, as Cornu suggests, with the bright line D3 of the chromo- 

 sphere. The y corresponds with a bright line also belonging to the 

 chromosphere and the solar corona; and, finally, 6 corresponds with 

 a line of the chromosphere. The line ^ alone stands unidentified with 

 any known line. 



VOL. XI. 5 



