8 



LIFE HISTORY OK THE STARS. 



But the scheme of research is the prime con- 

 sideration. Let us suppose, as in the case of the 

 Mount Wilson Observatory, that the chief object 

 is to contribute, in the highest degree possible, to 

 the solution of the problem of stellar evolution. 

 What was the origin of this earth on which we live? 

 We know that it is a member of a solar system, one 

 of several planets moving harmoniously about a 

 great central sun, on which they depend for light 



FIG. 3. Saturn. 



and heat. Hut how was the earth formed? 

 1 hrough what successive stages did it pass in its 

 early life? How were its constituent parts sepa- 

 rated from that great vaporous mass which, as 

 most astronomers believe, once united the planets 

 and the sun? By what process, extending over 

 millions of years, have the intensely hot solar gases 

 condensed toward a center, leaving behind those 

 rotating and revolving spheres, the planets and 

 their satellites? Or must this Laplacian view give 



