30 Repokt 8.A.A. Advancement of Science. 



separate orbs, granted a vast tidal distortion, and the life history of an 

 Algol star follows a path of development as rigidly defined as the life 

 history of a plant or an animal. 



A most interesting line of research has been opened up by the 

 suggestion that the variation of certain stars is due to spots on their 

 surface. Thus an analogy between the variation of our own luminary 

 and that of distant orbs is sought to be established. It is possible, 

 as we have already pointed out, that in this suggestion may lie the 

 explanation of long period \ariation. 



The problem whether variable stars are confined to a certain 

 region of space, the outer concentric area of our stellar universe, or 

 whether the}' are scattered at random through the chambers of space 

 is one of no ordinary interest. At present our knowledge is too meagre 

 to enable us even roughly to come to any judgment on the matter. 



Allied to this line of inquiry is that which seeks to establish a 

 connection between stellai- variation and the constitution of the stars. 

 Is it only stars of a certjiin class that vary — gaseous, nebular, solar, 

 as the case may be — or is variation common to all sorts and condi- 

 tions of stellar worlds I 



These and many other problems of deep interest indicate Ikjw 

 wide is the outlook of this particular science. It is only by years 

 and years of continuous and indefatigable labour that material will 

 be gathered which will avail in the solution of the great cosmic 

 <juestions which the study of stellar variation opens up. 



In the pure air and clear skies of South Africa there is abundant 

 room and a great field for innumerable workers. If what I have 

 said in this i)aper will add to the active interest in the science I will 

 consider myself indeed fortunate. 



