66 THE POPULAR SCIENCE MONTHLY. 



" If tliia interpretation were correct, the bright lines of the spectrum of the 

 star would comprise exclusively the brightest and most frequent lines, of the 

 chromosphere." 



In the extreme violet tliere is a line, the fourth of hydrogen, also 

 noted by Dr. Young, as one of the naost frequent in the spectrum of 

 the chromosphere, the wave-length of which is 410. Cornu thinks he 

 has often perceived this line in the spectrum of the star, hut he has 

 not been able to measure it. The distinguished observer closes his 

 account of these interesting researches as follows : 



" To sura up, the light of the star seems to have precisely the same composi- 

 tion as the light of the sun's envelope, the chromosphere. Though the tempta- 

 tion is strong to draw from this fact conclusions as to the physical condition of 

 this new star, its temperature, the chemical reactions it must exhibit, I will make 

 no comments, nor oflter any hypotheses. We lack, I think, the data necessary 

 for reaching a profitable conclusion, or at least a conclusion that can be verified. 

 However attractive such hypotheses may be, we must not forget that they He 

 outside of the domain of science, and that, instead of being of service to science, 

 they are likely to hinder its progress." 



The readers of La Nature will permit us to add a few reflections 

 of our own to those offered by our learned fellow-countryman. His 

 reserve we acknowledge to be very wise, but he has expressed him- 

 self a little too strongly. Who, after perusing M. Cornu's analysis 

 and the conclusions he has drawn, would not make the short step that 

 here intervenes between fact and hypothesis, and assert the similarity, 

 if not the identity, of the light of the star with that of the chromo- 

 sphere? True, we cannot with certaintj^ affirm that tlie apparently 

 continuous faint spectrum in which are seen the bright lines was also 

 its spectrum before it became visible to us, but that such is the case 

 is highly probable. We cannot say what was the cause of this sudden 

 development of gases, whose existence and incandescence are revealed 

 by the star's spectrum, just as we are as yet unable to assign the 

 cause of the sun's hydrogen protuberances. But is it nothing to class 

 together phenomena, the only difference between which seems to be 

 one of degree alone ? The hypotheses of Huggins and Miller, as to 

 the causes of the apparition of the star in the Corona Borealis, can of 

 course never be verified ; but no more can we verify the current 

 hypotheses held by astronomers and physicists with regard to the 

 presence of various chemical elements in the sun; we have here only 

 probabilities. Such hypotheses, far from being of injury to science, 

 are indispensable for its progress: they stimulate the observer's mind, 

 constantly suggest to him fresh observations, and become a hinderance 

 only when they are held to be demonstrated truths, and when men 

 refuse to give them up after they have been proved to be erroneous, 

 or after they have served their purpose. La Nature 



