1902.] On the Spark Discharge from Metallic Poles in Water. 31 



I On the Spark Discharge from Metallic Poles in Water." By- 

 Sir Norman Lockyer, K.C.B., F.B.S. Eeceived January 31, 

 —Bead March 6, 1902. 



[Plate 3.] 



During the appearance of the new star in the constellation Auriga, 

 which was discovered in January, 1892, the Kensington photographs 

 were the first* to show that several of the brighter lines were accom 

 panied by absorption lines on their more refrangible sides. 



This appearance I explained on the hypothesis that we were 

 dealing with at least two bodies, one giving a radiation, and the 

 other an absorption spectrum, the differential movements of which 

 could be determined by the changes of wave-lengths observed. 



In a paperf published in the year 1899, Dr. J. Wilsing made the 

 suggestion that, in view of the great velocities shown by the large 

 displacement of the lines in the spectra of new stars, and the occur- 

 rence of these displacements in the same direction, some other cause 

 of them was probably at work, and he suggested that the cause might 

 be high pressure, which drives the line towards the red. 



The First Observations of Nonsymmetrical Emission. 



The non-symmetrical development of emission lines is of frequent 

 occurrence in ordinary arc spectra. Typical photographs of such 

 phenomena were referred to by me in illustration of papers communi- 

 cated to the Boyal Society more than a quarter of a century ago on 

 peculiarities of emission and absorption spectra. I 



The following extracts from parts of these communications will 

 serve to indicate the facts observed at that time : — 



" Photographs showing Non-symmetrical Lines. 



" 1. Spectrum showing two Ag lines at about wave-lengths 4054*3 

 and 4210'0. Both lines are fluffy and reversed ; the less refrangible 

 line is much more strongly expanded on its more refrangible side, 

 and is carried up to a much greater height as a radiation line than its 

 other side. The more refrangible line is more symmetrical, but 

 presents the same phenomenon to some extent, only in the opposite 

 direction, its less refrangible side being the most developed. 



" II. Spectrum of Bb, showing line at wave-length 4202. Here 

 the two ends of the line are produced by radiation alone, the central 



* ' Roy. Soc. Proc.,' vol. 50, p. 434. 



t « Astrophys. Journ.,' vol. 10, p. 113, 1899. 



% « Phil. Trans.,' vol. 164, Part II, pp. 805-813, 1874 ; ' Roy. Soc. Proc.,' vol. 28, 

 pp. 428-432, 1879. 



