58 Mr. J. Norman Lockyer. On the Appearance of the 



those gases, and for the present, at all events, each of the three 

 series of helium or gas X may be taken to represent the vibrations 

 of molecules of the same gas but of different complexities. 



The differences in the stellar behaviour of helium and gas X have 

 been confirmed by reference to the researches of Professor VogeP 

 and Professor Pickering."]" 



I suggest that the time has come to give gas X a definite name. 

 It will be remembered that I pointed out in May, 1895, J that helium 

 was only one constituent of the gas discovered by Professor Ramsay, 

 which he imagined to consist of helium alone, and that there was 

 spectroscopic evidence suggesting at least one other new element 

 associated with helium. 



Afterwards, in September, 1895, Professors Runge and Paschen 

 came to the same conclusion, § but their work still left indeterminate 

 the number of elemental gases in the mixture. 



In the many comparisons of the lines I had to make in my investi- 

 gations I soon found the inconvenience of not having a name for the 

 gas which gave 667, 501, and other lines, and I called it gas X for 

 laboratory use. When, therefore, Professors Runge and Paschen, 

 who had endorsed my results, and had extended them, called upon 

 me, I thought it right to suggest to them that, sinking all questions 

 of priority, we should all three combine in suggesting a name for 

 this gas, the elemental character of which we had demonstrated. 



This offer they declined, || and so far as I was concerned the matter 

 dropped. 



In the meantime Dr. Stoney has suggested the name " parhelium." 

 But seeing that this word is already in use in another connection for 

 a " mock-sun," its acceptance is, I think, impossible. I propose, 

 therefore, the word " asterium," since it is in the stars that the 

 behaviour of the new element has been best studied, and its appear- 

 ance furnishes valuable evidence as to their chemistry. 



The probable Existence of other JSfeic Gases in the Hottest Stars. 



Discrimination between Gaseous and Metallic Lines. — The lines of 

 helium, asterium, and hydrogen in the hottest stars are accompanied, 

 as I have stated, by others which may either represent gases of a 

 similar character, or metals at very high temperatures. It becomes 

 important to consider the means at our command for distinguishing 

 between gaseous and the metallic lines. 



* ' Astrophysical Journal,' 1895, vol. 2, p. 333. 



f ' Annals of the Harvard College Observatory,' vol. 28, Part I. 



X ' Roy. Soc. Proc.,' vol. 58, p. 194. 



§ * Nature,' vol. 52, p. 321. 



j| ' Science Progress,' June, 1896, p. 278. 



