On the Photographic Spectrum of<y-Cassiopeice. 173 



December 13, 1894. 



Sir JOHN EVANS, K.C.B., D.C.L., LL.D., Vice-President and 

 Treasurer, in the Chair. 



A List of the Presents received was laid on the table, and thanks 

 ordered for them. 



The following Papers were read : 



I. " On the Photographic Spectrum of ry-Cassiopeise." By 

 J. NORMAN LOCKYER, C.B., F.R.S. Received November li, 

 1894. 



Introductory. 



In the Bakerian Lecture for 1888* I referred in some detail to the 

 spectrum of 7-Cassiopeia9, and suggested explanations of the origins 

 of the various lines which had been observed. At that time no photo- 

 graphs of the spectrum were available for discussion, but the ques- 

 tions raised by the eye observations were of such great interest that 

 I determined to attempt a photographic study of the spectrum. 

 This was commenced in November, 1888, and " has been continued at 

 intervals up to the present time. 



In view of the somewhat conflicting evidence of the variability of 

 the spectrum, it was considered necessary that the photographs 

 should extend over a considerable period before any serious attempt 

 was made to discuss them. Some of the results obtained, however, 

 now appear to be so definite that I have thought it desirable to com- 

 municate them to the Society at once. I therefore give particulars 

 of the inquiry so far as it has yet gone, and a brief account of other 

 observations is added, in order that the significance of the photo- 

 graphic results may be the better realised. 



In the paper referred to I gave an historical statement including 

 the early observations ; it is only necessary to add to this that the 

 spectrum has been since observed or photographed by Professor 

 E. C. Pickering, Professor Keeler, and Dr. Belopolsky. 



Professor Pickering makes no mention of dark lines, or of bright 

 lines other than F.f 



Professor Keeler, observing with the Lick refractor in 1889J failed 



* ' Roy. Soc. Proc.,' vol. 44, p. 43. 



f ' Draper Catalogue,' p. 266. 



J ' Publ. Ast. Soc. Pacific,' vol. 1, p. 80. 



