( 635 ) 



TABLE IV. 



Summing up we find: that the total numbers of stars of different 

 magnitude (Harvard scale) as derived from observation in Publications 

 of the Groningen Lnhoratory No. 18, are well represented by 

 adopting the luminosity -curve (2), with the values (4) of the constants 

 and the following values of the star-density : 



TABLE V. STAR-DENSITY. 



in which a(0)=^ 139.7. 



It would be interesting to investigate what are the changes that 

 can be made in these values without their ceasing to represent the 

 observed numbers satisfactorily. I have deferred this investigation for 

 the present because it will be desirable in such a discussion to 

 include also the data furnished by the parallaxes. 



