1904.] On the Temperature Classification of Stars. 



237 



Notwithstanding this difference the spectrum of t] Ursae extends 

 further into the ultra-violet than does that of Capella, and not only 

 does it extend further, but the maximum intensity is extended much 

 further into the ultra-violet than is that of Capella, which drops off 

 rapidly beyond K. 



No. 23. In this comparison the red part of the Procyon (third 

 stage) spectrum is much brighter than that of Alnitam (ninth stage). 

 The intensity in the longer portion of the spectrum of Procyon rises 

 at once to its maximum at H j8) has its centre of maximum at about 

 \ 460, and at H y commences to diminish towards the violet. In the 

 spectrum of Alnitam, however, the maximum is delayed until the 

 region about /\ 426 is reached, and is then sustained up to finally 

 extending to the ultra-violet with a marked superiority, comparatively, 

 over that of the Procyon spectrum. 



Extreme Interval. 



No. 33. This comparison of two type stars respectively situated 

 near the extremities of the temperature curve is naturally one of the 

 most striking pieces of evidence in support of this method of tempera- 

 ture classification. The spectrum of Alnitam (ninth stage) is nowhere 

 *so intense as the red and blue parts of the Aldebaran (second stage) 

 spectrum, and yet it extends more than twice as far towards the 

 ultra-violet, from H^, as the hydrogen series, whilst the more refrangible 

 limit of the Aldebaran spectrum only extends to K. The maximum 

 intensity of the blue portion of the Alnitam spectrum occurs much 

 nearer the ultra-violet than that of the Aldebaran spectrum, the latter 

 attaining its maximum at about A 465. 



8. Conclusions. 



It may be pointed out that the temperature classification, confirmed 

 by this research, does not agree with that published by Sir William 

 and Lady Huggins who, in their " Atlas of Representative Stellar 

 Spectra " containing " a Discussion of the Evolutional Order of the 

 Stars," place the solar stars on a higher temperature level than the 

 white stars. 



A reduction of intensity in the continuous spectrum beyond the 

 hydrogen series to which attention has been called by more than one 

 observer, Schumann* among others, does not affect the results which 

 I have stated. Another paper dealing with this and similar points is 

 in course of preparation. 



The result of the research may be stated as follows : — 

 Taking the stars assumed to be hottest in the chemical classification, 

 we find that in all cases the relative length of the spectrum is reduced, 

 * ' Smithsonian Contributions to Knowledge,' No. 1413, 1903, p. 23. 



