THE SEMI-CENTENNIAL ANNIVERSARY 67 



tion of stars. Since the exhaustion of the nebulous matter, 

 evidently there could be formed no more helium stars; and the 

 helium stars that had been formed developed gradually in the 

 second stage into first type stars, and in a short time there will 

 be an end to helium stars in those groups, and this will explain 

 perfectly how it is coming to pass at present, that we do not find 

 any helium stars in those groups. 



Therefore, finally, our answer to the question: how does it 

 come to pass that in the second stream or cloud we find hardly 

 any helium stars, would be because at some time the nebulous 

 matter must have been exhausted in this cloud. 



As to the first stream or star cloud, we similarly conclude that 

 the nebulous matter must not yet have been exhausted, or, if so, 

 only at a very recent period. 



It has been my aim to show, not that much has been done, but 

 that there is a beginning; not that we have entered far into the 

 promised land, the land lying open to the human view so tempt- 

 ingly since the first man looked up to the sky, but that a few 

 pathways are being mapped out, along which we may direct a 

 hopeful attack. Our problems now take a more definite form, 

 and even if we are never to solve them completely, let us remem- 

 ber the words of the poet: 



" If God held in His right hand all truth, and in His left nothing but the ever 

 ardent desire for truth, even with the condition that I should err forever, and bade, 

 me choose, I would bow down to His left, saying, ' Oh, Father, give, for truth is 

 but for Thee alone.' ' 



(Applause.) 



THE PRESIDENT: I am sure that you will all approve of my 

 action if I express the thanks of the Academy to Professor 

 Kapteyn for taking the trouble to come over here to talk to us 

 on this most inspiring subject. I can not imagine anything more 

 inspiring than the structure of the universe. I will give notice, 

 in accordance with the notice already given, that this is the 

 only lecture or address at this session. 



(Thereupon at 1 1 : 35 o'clock a. m. the session was adjourned.) 



