VI.] THE CHEMISTRY OF THE STARS. 65 



The Chemistry of the Cooler Stars. . 



I have shown, on page 57, how the discovery of new lines in the 

 spectra of the metallic elements by using the most powerful induction 

 coil in existence has put us in possession of the chemistry of stars of 

 intermediate temperature ; and, further, how the discovery of the 

 cleveite gases has helped us in tracing the origins of very many lines 

 of the hotter stars. 



Our knowledge of the chemistry of the cooler stars is little short of 

 marvellous ; we have two distinct groups of coolest ones, the evidence 

 of their much lower temperature being the shortness of their spectra. 

 In one of these groups we deal with absorption alone, as in those 

 already considered; we find an important break in the phenomena 

 observed ; helium, hydrogen, and the enhanced lines of metals have 

 practically disappeared, and we deal with metallic arc lines and carbon 

 absorption chiefly. 



But the other group of coolest stars presents us with quite new 

 phenomena. We no longer deal with absorption alone, but accompany- 

 ing it we have radiation, so that the spectra contain both dark lines 

 and flutings and bright ones. Now such spectra are visible in the case 

 of new stars, as they are called, the ephemera of the skies, which may 

 be said to exist only for an instant relatively. In the case of these 

 bodies, when the disturbance which gives rise to their sudden appear- 

 ance has ceased, we find their places occupied by nebulae ; we cannot, 

 therefore, be dealing here with stars like the sun, which has already 

 taken some millions of years to slowly cool, and requires more millions 

 to complete the process into invisibility. 



Hence in this class of coolest " stars " we are obviously dealing with 

 swarms of meteorites, the condensation of which has scarcely com- 

 menced, and hence it is that this class provides us with more " variable 

 stars " than any other. 



