Colours cf Stars. 109 



respect to the same material — at least at similar temperatures ; 

 so that the aspect of the lines of any spectrum, when analyzed 

 by a suitable apparatus, is an unerring indication, so far as is 

 yet known, of the presence of the material to which that set of 

 lines belongs. Hence, when among the multitude of lines- 

 contained in the solar spectrum, we are able to identify those 

 which are known to belong to the spectra of certain elementary 

 substances, we are naturally led to infer the presence of those 

 substances in the body of the sun.* Of course, before anything 

 like certainty can be ascribed to this inference, it must be 

 demonstrated that the lines appertaining to every element are 

 unchangeable, at least under any conditions fairly presumable 

 upon the solar surface ; and that one element alone is associated 

 with any given set of lines. 'The proof of the former of these 

 premises would be difficult; of the latter, while so many 

 unknown elements may exist, impossible. But we must be 

 content in this, as in many similar cases, with inevitable imper- 

 fection, and accept willingly the nearest approximation within 

 our reach, to a truth in its own nature apparently beyond 

 demonstration. This daring investigation into the nature of 

 the sun has now been for some time before the public, and 

 though it has been assailed with vigour, it seems to be gaining 

 ground, and likely to keep it : and it is truly interesting to learn 

 that by the most praiseworthy researches of two of our own coun- 

 trymen it has received an extension which might indeed have 

 been readily anticipated, but could only be effected through the 

 means of costly and laborious experiment. We now have 

 begun to study the constitution of the stars. Secchi and others 

 had already commenced this investigation, but, so far as we 

 know, no direct and simultaneous comparison had previously 

 been made of the lines visible in the various stellar spectra, with 

 those produced by terrestrial elements. This extremely 

 delicate and difficult research has been recently commenced^ 

 with most gratifying results, by the joint efforts of Mr. Huggins 

 and Dr. Miller. They entered upon their task, aided by an 

 8-inch object-glass of Alvan Clark, in January, 1862, and the 

 conclusions which they have already drawn are truly marvellous 

 ones, and such as reflect the highest honour upon the observers. 

 There seems as much reason to believe in the existence of the 

 metallic elements sodium, magnesium, calcium, iron, and bis- 

 muth in the atmosphere of Betelgeuse as in that of the sun I 

 To these Aldebaran adds hydrogen, tellurium, antimony, and 

 mercury. Sirius gives us sodium (which indeed seems to exist 

 everywhere), magnesium, hydrogen, and probably iron. Wega, 

 sodium, magnesium, and hydrogen. Other spectra have been 



* The question of absorption has been intentionally omitted, for the sake of 

 greater perspicuity. 



