METHODS IN MODERN PHYSICAL ASTRONOMY. 483 



yellow ones. In this manner the spectroscope may help us to esti- 

 mate in some degree the age of a sun, and measure the length of the 

 career which it has already accomplished. 



While studies of this kind were going on in France, spectrum 

 analysis was receiving magnificent developments in England, more in 

 the line which its authors had indicated. Messrs. Miller and Huggins 

 entered upon the study of the stars, and found in all of them which 

 they examined the solar elements in various combinations. This dis- 

 covery had an immense philosophical bearing, for it proved that the 

 matter forming the solar and the stellar world is obtained from the 

 same elements. It was a demonstration of the material unity of the 

 universe. The study was prosecuted still further. There are stars 

 which we regard as situated on the confines of the visible universe, 

 the light of which is so weakened by the immense journey it has to 

 make to reach us that they appear only as feeble glows. Mr. Hug- 

 gins succeeded in analyzing some of them, and showed that there 

 exists a whole class of nebulae which are really unresolvable into stars, 

 and are formed of incandescent gases, among which hydrogen, which 

 thus seems to be the principal element in the composition of the uni- 

 verse, is the most prominent. 



So the whole visible universe not only our central star and the 

 planets of our family, but those stars, too, which are so far off that 

 our most powerful telescopes can not give them a sensible diameter, 

 and those nebulae which only make a weak glow in our instruments 

 is reached by our chemistry, seized by our analysis, and made to fur- 

 nish the proof that all matter is one, and that these stars are made of 

 the same stuff as we. More, still, than this : at those great distances, 

 and in the presence of the vague and indefinite forms of the nebulae, 

 it would not be possible to study precise movements and discover 

 whether the great law of gravitation reigns in such remote regions. 

 Chemistry here comes to the aid of mechanics, and we may say boldly 

 that that matter, which is identical with ours, is subject, like it, to 

 the laws of gravitation. Certainly, when Newton decomposed a 

 beam of white light, and laid the first basis of the theory of the spec- 

 trum, he had not the slightest suspicion that his law of gravitation 

 would, at a later period, find in it wings to carry it into regions where 

 all measurement ceases and all calculation is powerless. 



Spectrum analysis, after having in this manner, in a few years, 

 gone through the universe and reaped the magnificent harvest I have 

 just described, now returns to the sun, the point whence it departed, 

 to take advantage of the opportunity afforded by eclipses. These 

 phenomena, it is well known, exhibit a collection of magnificent spec- 

 tacles of an extraordinary character, which had heretofore remained 

 unexplained. Those rosy-colored protuberances of strange forms which 

 surround the dark limb of the moon, that magnificent luminous corona, 

 those radiances in the form of a glory and extending to enormous dis- 



