Farther Observations on Nova Persei. 



143 



In the visible part of the spectrum the bright green-blue F line of 

 hydrogen has become more conspicuous as the neighbouring green 

 lines have become fainter, and the bright C line is intensely brilliant. 



From all these causes, which give us blue light on the one hand and 

 red on the other, the star should present to us the precise quality of 

 red which has been observed. 



Colour. 



At discovery the star was described as bluish-white. No observa- 

 tions on its variation in hue during its brightening were possible, 

 owing to unfavourable weather conditions. The observations during 

 the period of decline have indicated a change to the present colour of 

 a decided claret red. In comparison with this, it is interesting to note 

 that in the case of the Nova which appeared in 1604, Kepler alludes to 

 purple and red tints assumed by the star. 



Changes in the Photographic Spectrum. 



Between February 25th and March 5th, to take the extreme difference 

 of dates on which photographs were obtained, it has been noted that 

 while some of the dark lines were absent at the later date, either new 

 lines had come in or previously feeble lines had become intensified. 

 There has not yet been time to determine accurately the positions of 

 these lines (see Plate 1). 



The appearance of the bright lines of hydrogen which I described 

 as being reversed on February 25th, had very materially changed by 

 March 3rd. 



In inspecting the dark band representing the bright hydrogen at He 

 two darker fine lines are seen nearly coincident in position with the 

 edges of He in the spectrum of a Persei. 



To my eye the light curve is as follows : — 



red. 



The appearance is different in the case of the F line (H/3), a 

 light curve of which I also give — 



