232 



Sir Norman Lockyer. 



The Photographic Spectrum. 



On March 6th the photographs were very similar to those obtained 

 in the earlier stages, the only apparent difference being in the relative 

 intensity of the bright hydrogen lines as opposed to those having other 

 origins, most of which have been shown to be probably due to iron and 

 calcium. The hydrogen lines have sensibly brightened, while the others 

 have become much feebler. 



The photograph of March 10th shows a further dimming of the 

 bright lines other than those of hydrogen. 



On March 25th, when the next good photograph was taken, the 

 spectrum had undergone great modifications. The hydrogen lines are 

 still very bright, though they do not show the structure which they did 

 in the photographs taken between February 25th and March 10th, 

 The bright lines other than those of hydrogen, which are seen in the 

 earlier photographs, have now disappeared, and other lines become 

 visible. The continuous spectrum has also greatly diminished. 



Approximate determinations of the wave-length of these new lines 

 have been made by Mr. Baxandall by comparison with lines of known 

 wave-length in the spectra of a and e Persei photographed with the 

 same instrument. They are as follows : — 



X 



3870. Broad, and merging into H£ (3889). 

 4367. Weak. 



4472. Not very strong. Probably helium (X 4471-6). 

 4565. Weak. 



4650. Very strong broad line. Possibly the 465 line of the bright- 

 line stars and the belt stars of Orion. 



4690. Moderately strong. Possibly new hydrogen (A. 4687 - 88) seen 

 in bright-line stars and some Orion stars. 



471. Weak. Probably helium (X 4713). 



The hydrogen lines in the spectra are H£, He, HS, Hy, and H/3. 

 • The lines at X 3870 and 4650 are perhaps identical with those 

 observed by von Gothard* in the spectrum of Nova Aurigse after it 

 had become nebular, but associated with these lines in his record is the 

 chief nebular line at 5007, no trace of which is yet visible in the photo- 

 graphs of the spectrum of Nova Persei. On the other hand, 

 which is the brightest line in the present spectrum of Nova Persei, 

 does not appear at all in von Gothard's spectrum of Nova Aurigae. 



Characteristics of the Hydrogen Lines. 



In my former paper I referred to the structure of the broad bright 

 lines of hydrogen. A more detailed examination of the lines as photo- 



* « Ast.-Phys. Joar.,' vol. 12, 1893, p. 51. 



