126 PLEASANT WA YS IN SCIENCE. 



could possibly cool in any great degree while enormous 

 quantities of gas more intensely heated (by the hypothesis) 

 remained around the star. The more rapid decrease in the 

 violet and blue parts of the spectrum than in the red and 

 orange is explicable as an effect of absorption, at least as 

 readily as by the hypothesis that burning solid or liquid 

 matter had cooled. Vogel himself could only regard the 

 other bands which crossed the spectrum as absorption-bands. 

 And the absorption of light from the continuous spectrum 

 in these parts (that is, not where the bright lines belonging 

 to the gaseous matter lay) could not possibly result from 

 absorption produced by those gases. If other gases were 

 in question, gases which, by cooling with the cooling surface, 

 had become capable of thus absorbing light from special 

 parts of the spectrum, how is it that before, when these 

 gases were presumably intensely heated, they did not in- 

 dicate their presence by bright bands? Bright bands, in- 

 deed, were seen, which eventually faded out of view, but 

 these bright bands did not occupy the position where, later 

 on, absorption-bands appeared. 



The natural explanation of what had thus far been ob- 

 served is different from that advanced by Vogel, though we 

 must not assume that because it is the natural, it is necessarily 

 the true explanation. It is this that the source of that 

 part of the star's light which gave the bright-line spectrum, 

 or the spectrum indicative of gaseity, belongs to the normal 

 condition of the star, and not to gases poured forth, in con- 

 sequence of some abnormal state of things, from the sun's 

 interior. We should infer naturally, though again I say not 

 therefore correctly, that if a star spectroscope had been 

 directed upon the place occupied by the new star before 

 it began to shine with unusual splendour, the bright-line 

 spectrum would have been observed. Some exceptional 

 cause would then seem to have aroused the entire surface 

 of the star to shine with a more intense brightness, the 

 matter thus (presumably) more intensely heated being such 

 as would give out the combined continuous and bright-line 



