178 



Mr. J. Norman Lockyer. 



Tliese phenomena are illustrated in Map III by photographs of 



the spectra of typical stars. 



The facts recorded in the photographs of each star are as follows : — 

 Starting with Bellatrix, magnesium is solely represented by the 



enhanced line at 4481, which is relatively feeble, calcium by the 



H and K lines, also feeble, while there are no indications of iron 



at all. 



Passing next to ft Persei, 4481 and the H and K lines are in- 

 tensified, while the enhanced lines of iron are added. 



In 7 Lyrse, all the enhanced lines of magnesium, calcium, and iron 

 are strengthened. 



A further intensification of the enhanced lines occurs on passing to 

 Sirius, but here the characteristic arc lines of all three substances are 

 added, indicating a temperature intermediate between that of the 

 experimental spark and that at which the enhanced lines appear 

 alone. 



With a farther slight fall of temperature, represented by Castor, 

 the enhanced lines become slightly stronger, as do also the charac- 

 teristic arc lines. 



At the still lower temperature of Procyon there is a marked 

 increase in the intensity of the characteristic arc lines and a decrease 

 in the intensity of the enhanced lines, except in the case of H and K, 

 which, as already pointed out, are strong lines in the arc. 



Finally, at the temperature of Arcturus, or the sun, the enhanced 

 lines of maguesium and iron are either very faint or entirely absent, 

 while H and K remain visible for the reason already stated, and the 

 arc lines of all three metals become very strong. 



Cleveite Gas Results. 



The appearance of the lines of the cleveite gases in the stars of 

 decreasing temperature already considered is restricted to ft Persei 

 and 7 Lyras. An attempt is made to show their chp.nges of intensity 

 in Map YI, which also includes Bellatrix as representative, for the 

 present, of the highest temperature. 



Starting with Bellatrix, the lines of the cleveite gases are very 

 strong, while, on passiug to the cooler sta.rs, they rapidly become 

 weaker, as the enhanced metallic lines continue to get stronger. In 

 fact, the lines of the cleveite gases disappear at a comparatively early 

 stage, long before the absorbing metallic vapours are cool euough to 

 show any traces of the characteristic arc lines. 



In ft Persei, as shown on the map, the cleveite gas lines are much 

 weaker than iD Bellatrix, while in 7 Lyrse they are on the verge of 

 disappearance. No certain indications of the cleveite gas lines have 

 been found in Sirius, Castor. Procyon, or Arcturus. A special search 



