iSo/ar and Flanetary Evolviloii. 



m 



tent of the universe. Are there an infinite nnmher of 

 worlds, extending beyond our ntniost vision ? We cannot 

 know. All the objects within the reach of the most power- 

 ful telescopes belong to our universe. It is possible that 

 other universes exist beyond, which we are unable to per- 

 ceive because of the absence of a luniiniferous ether, con- 

 necting them with our range of vision. It is an interest- 

 ing question whether our universe is still young and grow- 

 ing, or whether it is now on its downward course, tending 

 to decay and death, liespecting this question it may be 

 said that we find within the range of vision very few dead 



Fig. 13. Spiral nebula in Canes Yenatici. 



stars, while the number of nebula? in process of forming 

 into stars is very great. AVe may therefore assume that 

 the universe is still in a yovithful condition and has not 

 ])assed the noon of its existence. The spectroscope assvires 

 us that those stars which shine with a red liglit are the old- 

 est, and the nearest extinction. Of these there are com- 

 paratively few. 



We have brought the history of a planet from the i)eriod 

 of its primal evolution out of the fiery mist, to its extinc- 

 tion. Is this all ? AVill there be no resurrection of dead 

 worlds ? AVhen a planet like the moon has parted with its 

 heat it will still continue to rotate on its axis and to re- 



