CELESTIAL EVOLUTION. 23*7 



inclinations in the satellite systems increase with 

 distance from the primary ; the outer planets 

 show a greater tilt of axis to orbit-plane with 

 increased distance from the Sun (so far as detect- 

 able) ; the inner planets show a similar relation." 



The fate of the average solar star is sketched 

 out by Vogel's classification, and by any evolu- 

 tionary hypothesis which we may adopt. In the 

 words of Lowell : " Though we cannot as yet 

 review with the mind's eye our past, we can, to 

 an extent, foresee our future. We can with 

 scientific confidence look forward to a time when 

 each of the bodies composing our Solar System 

 shall turn an unchanging face in perpetuity to 

 the Sun. Each will then have reached the end 

 of its evolution set in the unchanging stare of 

 death. Then the Sun itself will go out, becom- 

 ing a cold and lifeless mass ; and the Solar 

 System will circle unseen, ghostlike, in space, 

 awaiting only the resurrection of another cosmic 

 catastrophe." 



As to what this cosmic catastrophe will be, 

 science gives no definite idea ; nor can astrono- 

 mers say with certainty whether the Universe 

 will come to an end by the extinction of its 

 luminaries, or whether the suns and planets 

 will be brought back to luminosity again ; but 

 the human mind shrinks from the idea of a 



