PRESIDENT S ADDRESS. 7 



the problem of stellar movements and groupings are those that 

 in days to come will yield the best results. 



Already Halm has been enabled, from the spectroscopic data 

 at his disposal, to come to two very far-reaching conclusions. 

 First, the two streams discovered by Kapteyn are not sym- 

 metrical with regard to the sun, that is, they are not equally 

 distributed in space. 



They have, instead, their own definite locus, their own celestial 

 basin. Second, there are more than two streams of stars. One 

 is tempted to speculate on the future of this region of research. 

 Shall we some day be able to distinguish, not three streams of 

 stars, but three thousand? Shall we so enlarge our boundaries 

 that at no very remote day astronomers will be taken up mainly 

 with realms and kingdoms of stars, defining their boundaries, 

 determining their size, deducing their age, foretelling their des- 

 tination in time and space. Already something has been done in 

 this direction. The stars have been grouped according to their 

 spectroscopic characteristics, that is, according to their composi- 

 tion : and it is found that their proper motions are most intimately 

 connected with their size and structure. Stars of a certain type, 

 heavy, massive stars, move slowly through space ; stars of another 

 definite type move more rapidly. Once more, it is a Cape 

 Astronomer who is bent on running this relation to its cause. 



Halm has on hand an investigation in which proper motion is 

 held to be a function of the state of evolution of each star. 



The investigation is purely a dynamical one, based on the 

 Maxwellian law of the distribution of velocities. 



When in this connection we consider that, a hundred years 

 ago, men despaired of ever fathoming the abyss that lies between 

 us and the outposts of the stars : that spectroscopy is only fifty 

 years old ; that stellar photography has not been in use for more 

 than a quarter of a century, it is impossible to say what even a 

 decade may bring to us of advance and discernment. 



The matter of photographing the stars has naturally been 

 referred to again and again. We have said that in South Africa 

 it was born, born the hour Gill looked upon the photograph of the 

 1882 comet, taken with an ordinary portrait camera, and saw as 

 in a vision, the power of the new arm. 



The first comprehensive photographic survey of the heavens 

 was taken at the Cape. 



The present great international photographic star map, a 

 labour that will take three decades to complete, that will cost over 

 three quarters of a million adequately to finish, but which will 

 put on permanent record at least 15,000,000 stars, had its incep- 

 tion and its stimulus at the Cape. 



In exact astronomy, or fundamental astronomy, as it is often 

 called, there has been a brilliant succession of men in South 



