1904.] On the Temperature Classification of Stars. 



229 



containing the hottest stars, on the dissociation hypothesis, being placed: 

 at the top of the curve. It will be convenient to reproduce this table 

 here. 



10 Argonian 

 9 Alnitamian 



Achernian 

 Algol ian 

 f\ Markabian 



Sirian 

 (J Procyonian 



Arcturian 



I 



Piscian 



8 



Crucian 



7 



Taurian 



6 



Eigelian 



5 



Cygnian 



4 





3 



Polarian 



2 



Aldebarian 



1 



Antarian 



Metallic Stars 

 Stars with fluted spectra 



There was abundant chemical evidence to show that the mean 

 temperature of the stars occupying the same height on both branches 

 of the curve was not very different, so that we have ten horizons, or 

 stages, of mean temperature indicated in passing from the complete 

 fluted spectra of Antarian -Piscian stars to the simplified line spectra of 

 the y Argus type. 



So far as we could judge from the photographs then available, the 

 chemical changes gave a sequence identical with that desired for the 

 length of ultra-violet spectra in 1892, so that the latter classification 

 was fully justified by the test which had been applied to it. 



2. Aims and Conditions of the Present Research. 



As before mentioned in the work of 1892, the relative lengths of the 

 ultra-violet spectra were determined from photographs secured with 

 instruments having glass optical parts. It was possible therefore 

 to secure still another test by obtaining a new set of photographs 

 using calcite and quartz in place of glass, to enable the far ultra-violet 

 to be obtained and studied. Nor was this all, it seemed of the first 

 importance to utilise not only the length of spectrum in the blue, but 

 the relative brightness of the different parts. What happens regarding 

 the relative brilliancy of the different parts of the spectrum, as well as 

 the extension into the ultra-violet by increased temperature, was very 



