136 The Stars around the North Pole [April 24, 



(7) When, however, the luminosity of the stars in a given volume 

 of s])ace is considered, there are found to be far more faint than 

 briirht stars. There is no contradiction between this conclusion and 

 the last one, because the more distant bright stars are visible, while 

 we only see the faint ones which are comparatively near. 



(s) Evidence has been found that the stars thin out very materi- 

 ally at great distances from the sun. 



" 26. These conclusions are in harmony with the conception of a 

 finite stellar universe. Most of the stars we see and a great many 

 fainter ones are within the distance of 1000 parsecs. Doubtless the 

 stars extend to much greater distances, perhaps 10 times as far or 

 farther, but we can hardly doubt that we are near the middle of a 

 finite group of stars, and that the extent of this group is of the order 

 of 1,000 to 10,000 parsecs. 



It has been suggested, though the opinion is a speculative 

 one, that the Andromeda Nebula, and Spiral Nebulae in general, may 

 be similar groups of stars separated by vast intervals of empty space 

 h'om the stellar system to which we belong. If this is the case, we 

 may suppose that our system of stars, as seen from outside (say a 

 distance of the order of 100,000 parsecs), would present an appear- 

 ance similar to that of the Andromeda Nebula as seen from the earth. 



[F. W. 1).] 



