532 



tlie numbers in each column, as has been already observed, agree 

 witli each other. If onr conclusion that the frequency curve of the 

 absolute magnitudes does not vary with r, is right, we may derive 

 from the agreement of the luminosity curves in the different shells 

 that there is no perceptible absorption of light in space. 



In figure 1 the frequency curves that were found liave been 

 drawn. The six lines in the lowest part of the figure refer to the 

 determination of the luminosily curve, discussed in this essay. The 

 six lines in the upper part refer to an application of Schvvahzschild's 

 method to the same data, which will be explained in a following 

 communication. 



The line representing our determination of the luminosity curve 

 for the whole sky, indicates the logarithm of the number of stars 

 of every M per unit of volume in the neighbourhood of the sun. 

 For the other curves we added, in order to make comparison pos- 

 sible, a constant amount to each number. 



Ainsterdam, June 1918. 



