47 ' 



our research to more clusters. It will then also be possible to 

 investigate, how far our results give sup|)ort to the well-known 

 theory of giant and dwarf stars. 



From the figure subjoined it is evident that the luminosity curves 

 of the various clusters greatly resemble that found by Prof. Fvaptkyn 

 for the stars in the neighbouihood of the sun. And so this method 

 of determining the parallax, proposed l)y Prof. Kaptkvn, is justified. 



In the graphical representation Nm means the number of stars 

 from the brightest star to the absolute magnidide under consideration. 

 As it is only our purpose to compare the relative frequencies of 

 the various absolute magnitudes, we added in each curve a constant 

 amount to log. -Vj/. 



Amsterdam, December 1917. 



