49 



labor in measuring the positions of 454,875 stars 

 on these photographs, Kapteyn turned his atten- 

 tion to the study of stellar motions. He found, 

 in brief, that all the stars whose motions were 

 known belonged in one or the other of two great 

 intersecting streams, which have been moving 

 through space since time immemorial. Projected 

 back into the positions which they occupied in the 

 remote past, these stars represent two great sys- 

 tems, which drew toward one another, interpene- 

 trated, and now continue toward their unknown 

 goals. 



This impressive result, with its strong appeal to 

 imaginations curious as to the past or the future, 

 was but a single step in Kapteyn's progress. His 

 plans involved the study of great numbers of 

 stars, uniformly distributed over the heavens and 

 embracing questions of brightness, of distance, 

 and of motion. Through the cooperation of many 

 astronomers the necessary measurements to solve 

 these questions will ultimately be obtained. But 

 the great light-collecting power of our 6o-inch 

 reflector and the facilities provided for its use indi- 

 cated that it might prove of special service in the 

 realization of Kapteyn's hopes. Could this help 

 be given without loss to our own enterprise? 



STELLAR EVOLUTION. 



For it will be observed that Kapteyn's project dif- 

 fered materially from our own. He was occupied 

 with such questions as the limits of the universe, 



