48 



other in their appeal to the observer and tend to 

 scatter and exhaust his efforts? The simplest and 

 most obvious step would be to make just such a 

 study of the physical phenomena of selected stars, 

 representing different phases of evolution, as we 

 are now making of the sun. In spite of the neces- 

 sity, because of their feeble brightness, of basing 

 our conclusions on spectra a few inches long, repre- 

 senting the combined light from all parts of the 

 stellar disks, material progress could be made in 

 this way. But the importance of making the 

 most effective use of our instrumental equipment 

 and of accomplishing the greatest possible advance 

 within a limited period of years led to the post- 

 ponement of most of this work and the immediate 

 adoption of a different plan. 



THE STRUCTURE OF THE UNIVERSE. 



A great Dutch astronomer, gifted with a power- 

 ful scientific imagination, had been engaged for 

 many years in the study of the structure of the 

 universe. The fact that he had no telescope or 

 other observatory equipment did not hamper in 

 the least his ambitions or his successes. On the 

 contrary, it led to his cooperation with astronomers 

 in various parts of the world, who gladly contrib- 

 uted toward the realization of his far-reaching 

 projects. Kapteyn's first ally w T as the late Sir 

 David Gill, Astronomer Royal at the Cape of Good 

 Hope, who had photographed the whole of the 

 southern heavens. After twelve years of patient 



