9 



way to the radically different conceptions of the 

 planetesimal hypothesis? What is the nature of 

 the central sun, on which our lives depend ? What 

 is its relationship to other stars, and what part 

 does it play in the universe? How is this universe 

 organized, what bodies does it comprise, what is 

 its structure, and what are its bounds? If the 

 processes of creation and evolution are still at work 

 within it, may we not expect to find existing exam- 



FIG. 4. Nebula N. G. C. 7217. 



pies of the various stages through which our own 

 solar system has passed ? And may we not hope, 

 by learning the relationship of stars in moving 

 groups, and by tracing these groups back to their 

 former positions in space, to reconstruct a picture 

 of the universe as it was long before the solar sys- 

 tem had taken form? 



A large project, it may be said, too ambitious for 

 the ideal of any institution. But while no single 



