THE CENTURY'S PROGRESS IN ASTRONOMY 



purely gaseous stars of more recent discovery, which 

 Professor Pickering had specially studied. Zollner's 

 famous interpretation of these diversities, as indicative 



SPECTRA OF STARS IN CARINA 



of varying stages of cooling, has been called in question 

 as to the exact sequence it postulates, but the general 

 proposition that stars exist under widely varying condi- 

 tions of temperature is hardly in dispute. 



73 



