On the Chemical Classification of the Stars. 



187 



Certain unknown elements (probably gaseous, unless their lines 

 represent " principal series ") in the hottest stars, and the new form of 

 hydrogen discovered by Professor Pickering (which I term " proto- 

 hydrogen " for the sake of clearness), hydrogen, helium, asterium, 

 calcium, magnesium, oxygen, nitrogen, carbon, silicium, iron, titanium, 

 copper, manganese, nickel, chromium, vanadium, strontium ; the 

 spectra being observed at the highest available spark temperatures. 

 The lines thus observed I term "enhanced" lines, and I distinguished the 

 kind of vapour which produces them by the affix " proto," e.g., proto- 

 magnesium, for the sake of clearness.* 



Iron, calcium, and manganese at arc temperatures. 



Carbon (flutings) at arc temperatures. 



Maganese and iron (flutings) at a still lower temperature. 



In a communication to the Society! I stated the results arrived at 

 recently with regard to the appearances of the lines of the above sub- 

 stances in stars of different temperatures, and the definition of the 

 different groups -or genera to be subsequently given are based upon 

 the map which accompanied the paper, together with more minute 

 inquiries on certain additional points, the examination into which was 

 suggested as the work went on. 



So far as the inquiry has at present gone, the various most salient 

 differences to be taken advantage of for grouping purposes are repre- 

 sented in the following stars, the information being derived from the 

 researches of Professor Pickering J and Mr. McClean,§ as well as from 

 the Kensington series of photographs. 



Hotted Stars. 



Two stars in the constellation Argo (£ Puppis and y Argus ||). 



Alnitam (e Orionis). This is a star in the belt of Orion shown on 

 maps as Alnilam. Dr. Budge has been good enough to make inquiries 

 for me, which show the change of word to have been brought about by 

 a transcriber's error, and that the meaning of the Arabic word is "a 

 belt of spheres or pearls." 



* 'Boy. Soc. Proc.,' vol. 64, p. 398. 



f ' Eoy. Soc. Proc.,' vol. 64, p. 396. 



X ' Astro-phys. Journ.,' toI. 5, [). 92, 1897. 



§ ' Spectra of Southern Star?.' 



|| The spectrum of this star contains bright lines, but I show in a paper nearly 

 ready for communication to the Society, that when these occur with dark lines, 

 the latter alone have to be considered lor purposes of chemical classification. 



