1 10 PLEASANT WA YS IN SCIENCE 



be in an abnormal condition. It gave the rainbow-tinted 

 streak crossed by dark lines, which is usually given by stars 

 (with minor variations, which enable astronomers to classify 

 the stars into several distinct orders). But superposed upon 

 this spectrum, or perhaps we should rather say shining 

 through this spectrum, were seen four brilliant lines, two 

 of which certainly belonged to glowing hydrogen. These 

 lines were so bright as to show that the greater part of the 

 light of the star at the time came from the glowing gas or 

 gases giving these lines. It appeared, however, that the 

 rainbow-tinted spectrum on which these lines were seen was 

 considerably brighter than it would otherwise have been, in 

 consequence of the accession of heat indicated by and 

 probably derived from the glowing hydrogen. 



Unfortunately, we have not accordant accounts of the 

 changes which the spectrum of this star underwent as the 

 star faded out of view. Wolf and Rayet, of the Paris 

 Observatory, assert that when there remained scarcely any 

 trace of the continuous spectrum, the four bright lines were 

 still quite brilliant But Huggins affirms that this was not 

 the case in his observations; he was "able to see the contin- 

 uous spectrum when the bright lines could be scarcely 

 distinguished." As the bright lines certainly faded out of 

 view eventually, we may reasonably assume that the French 

 observers were prevented by the brightness of the lines from 

 recognizing the continuous spectrum at that particular stage 

 of the diminution of the star's light when the continuous 

 spectrum had faded considerably but the hydrogen lines 

 little. Later, the continuous spectrum ceased to diminish in 

 brightness, while the hydrogen lines rapidly faded. Thereafter 

 the continuous spectrum could be discerned, and with greater 

 and greater distinctness as the hydrogen lines faded out 



Now, in considering the meaning of the observed changes 

 in the so-called " new star," we have two general theories to 

 consider. 



One of these theories is that to which Dr. Huggins 

 would seem to have inclined, though he did not definitely 



