THE 



POPULAR SCIENCE 

 MONTHLY. 



JUNE, 1873. 



THE CONSTITUTION OF NEBULAE. 



By De. H. SCHELIsEN.i 



WHEN the starry heavens are viewed through a telescope of 

 moderate power, a great number of stellar clusters and faint 

 nebulous forms are revealed against the dark background of the sky 

 which might be taken at first sight for passing clouds, but which, by 

 their unchanging forms and persistent appearance, are proved to be- 

 long to the heavenly bodies, though possessing a character widely dif- 

 fering from the point-like images of ordinary stars. Sir William Her- 

 schel was able, with his gigantic forty-foot telescope, to resolve many 

 of these nebula? into clusters of stars, and found them to consist of 

 vast groups of individual suns, in which thousands of fixed stars may 

 be clearly separated and counted, but which are so far removed from 

 us that we are unable to perceive their distance one from the other, 

 though that may really amount to many millions of miles, and their 

 light, with a low magnifying power, seems to come from a large, faint- 

 ly-luminous mass. But all nebulse were not resolvable with this tele- 

 scope, and, in proportion as such nebulae were resolved into clusters 

 of stars, new nebulse appeared which resisted a power of 6,000, and 

 suggested to this astute investigator the theory that, besides the 

 many thousand apparent nebulas which reveal themselves to us as a 

 complete and separate system of worlds, there are also thousands of 

 real nebulae in the universe composed of primeval cosmical matter out 

 of which future worlds were to be fashioned. 



Lord Rosse, by means of a telescope of fifty-two feet focus, of his 

 own construction, was able to resolve into clusters of stars many of the 

 nebulae not resolved by Herschel ; but there were still revealed to the 

 eye, thus carried farther into space, new nebulae beyond the power 

 even of this gigantic telescope to resolve. 



1 Abridged from Schellen's " Spectrum Analysis." 

 vol. m. 9 



