236 



Sir Norman Lockyer. 



[Jan. 30, 



stage), and yet the latter extends as far into the ultra-violet as the 

 former. 



Furthermore, the intensity of the blue part of the spectrum of 

 Capella rises to its maximum immediately at and commences to 

 decline towards the violet at H y , whereas the maximum region 

 of Castor does not commence at once after leaving the green gap, and 

 attains its centre at about A 422. 



It will be observed that whether we take Arcturus or Capella to 

 represent Stage 2, the spectra of stars of higher stages have relatively 

 longer ultra-violet and reduced red radiation. It has to be noted, 

 however, that there are indications that Stage 2 will, as a result of 

 further work, have to be divided, for Capella is certainly hotter than 

 Arcturus as determined in the manner now under discussion. 



Stage 4 to Stage 6. 



No. 11. On examination of this negative it is seen that the detached 

 red portion of the spectrum of Sirius (fourth stage) is decidedly more 

 intense than the same portion of the Rigelian spectrum (sixth stage). 

 In the ultra-violet, however, we find that although both stars are 

 fairly high on the temperature curve, and, therefore, both spectra 

 extend far into the ultra-violet, the extension of the spectrum of Eigel 

 is more intense and greater than that of Sirius. 



Stage 6 to Stage 9. 



No. 35. By reason of its greater exposure the spectrum of Rigel 

 (sixth stage) is generally much stronger than that of k Orionis (ninth 

 stage), and especially is this so in the red portions of the two spectra. 

 This inequality notwithstanding, the spectrum of k extends practically 

 as far into the ultra-violet as that of Rigel. 



Various Intervals. 



No. 34. In a Ursse (second stage) the red part of the spectrum is 

 comparatively very bright, nearly as bright as the region between 

 G and F. In y Ursse (sixth stage) this red portion is barely visible. 

 Again, in the a Ursse spectrum the maximum occurs at X 460, and then 

 the intensity gradually declines to K, beyond which it is very faint. 

 The maximum intensity of the y Ursse spectrum is situated at about 

 A. 422, and it extends without becoming greatly impaired to He. 



No. 36. In this comparison we have a very striking case. The 

 spectrum of Capella (second stage) is compared with that of rj Ursse 

 Mai oris (eighth stage) ; Capella has been over-exposed, so that the 

 red portion is abnormally intense, t] Ursse Ma j oris received the 

 correct exposure, and the red part of the spectrum is rather faint. 



