THE UNIVERSE OF STARS. 545 



THE UNIVERSE OF STARS.* 



IT is only, curiously enough, witliin tlie last decade or two that 

 the science of astronomy has answered to its name. Until the 

 methods of spectrum analysis and of photography were applied to 

 the stars, astronomers were scarcely justified in their title, for 

 they knew little about the stars, and, hardly hoping to know 

 more, almost confined their attention to the solar system. Now, 

 although sidereal astronomy, the science of astronomy jjar excel- 

 lence, is still in its infancy, we may discern pretty clearly what 

 will be the nature of its achievements. Surpassing the wildest 

 dreams of the older astronomers in range and penetration, mod- 

 ern astronomy yet brings the whole cosmos within the grasp of 

 human intelligence. Not only are the stars in process of being 

 numbered, their motions, proper and relative, in course of meas- 

 urement, their physical constitution subjected to analysis, and 

 their distances brought within computation ; but the entire side- 

 real system is recognized as limited in extent, and the form and 

 magnitude of the vast group in space will at no distant date be- 

 come susceptible of approximate delineation and calculation. 



Of the methods referred to, photography has had, perhaps, the 

 largest share in the recent advancement of sidereal science. The 

 chemistry of the stars, it is true, is founded wholly on spectrum 

 analysis, that profound and searching means of testing the com- 

 position of bodies by the action of elementary substances, under 

 proper conditions, upon the infinitesimal undulations which give 

 rise to the phenomena of light ; but without the aid of photog- 

 raphy, the mapping of star-spectra must have remained a slow 

 and inaccurate process. The camera, on the other hand, has re- 

 vealed almost all that is known concerning the number, distances, 

 masses, and motions of the stars ; the lens has no " personal equa- 

 tion," and never gets tired ; sensitized gelatin responds with 

 infinite celerity to the undulations which make no impression 

 whatever upon the eye ; and star-pictures of the heavens are not 

 only permanent records, but, with the proper instruments and 

 skill, can be so readily taken that before very long it is probable 

 that some seven hundred thousand out of the whole sixty millions 

 of stars will be accurately charted and indexed. 



For such is the least number of the heavenly host — which a 

 French astronomer somewhat extravagantly estimates to contain 

 nearly seventy thousand millions of suns ; for each star we see is 

 a sun shining with its own light, and governing probably, like 

 our own, the motions of a system of planets. Nor is the light 



* The System of the Stars. B7 Agues M. Gierke. London : Longmans. 1890, 



VOL. XL. — 38 



