On the Chemistry of the Hottest Stars. 



171 



j 8ELUTRIX | ' , j 



I .. t , . j | - | -j | 



4 TA'JRf 



\x,t- ■ ■] : ' .4 ..... , 



r ( LEONIS j 



~\ ■ . I 



CAS"X'*UNlS 2. HFIUUM LINES i. 



Map II. — Behaviour of lines of cleyeite gases in stars of increasing temperature. 



helium lines, they steadily increase in intensity up to the highest 

 temperature in the case of the stars already discussed. At all stages 

 where the lines of helium and hydrogen appear together, the hydro- 

 gen lines are the stronger, so far as our present information goes, but 

 they do not reach their maximum intensity in any of the stars we 

 are now discussing. 



YI. Comparison of the Metallic Results with those given by the 

 Cleveite Gases and Hydeogen. 



The Cleveite Gases. 



Dealing with the stars already considered, a comparison of the 

 metallic and cleveite gas lines indicates that as the former die out 

 the latter are strengthened. 



The cleveite gas absorption first makes its appearance, very feebly, 

 in the stars in which the enhanced lines of magnesium and iron are 

 strongest, as in ex. Cygni. Then, as the temperature increases, as 

 demonstrated by the expansion into the ultra-violet of the continuous 

 radiation, the lines of the cleveite gases become stronger as the 

 metallic lines thin out. 



At the highest temperature, taking Bellatrix for the present as a 

 typical case, the principal helium lines are almost as strong as the 

 lines of hydrogen, while the enhanced lines of iron have quite dis- 

 appeared, and those of magnesium and calcium nearly so. These 

 variations are indicated in Map III. 



