63 
distance; but here the discontinuity already spoken of, and the lack 
of counts for fainter stars makes the explanation of the data uncertain. 
Of course the results of this first investigation have only a 
provisional character, and that for two reasons. In the first place 
by the incompleteness of the data: while up to the 9th magnitude 
the Durchmusterung Catalogues afford a rather complete though 
coarse material (by the uncertainty of the reduction to the photo- 
metric scale), we have hardly any data for the 10% and 11' magnitude. 
For the fainter classes the Selected Areas form an excellent but 
very limited material, while it is uncertain in what degree the local 
irregularities vary the average values for greater regions. Thus 
we do not know the whole course of A(m) from the 6" to the 
14% magnitude, which would be necessary to remove all doubts 
on the course of Z (9). 
In the second place it must be emphasized that by taking together 
extended space-sectors with artificial boundaries the real irregularities 
in the distribution of the stars, with perhaps wholly different boun- 
daries may be partly effaced, partly changed in their character. 
Moreover by regarding the influence of near absorbing nebulae and 
of remote galactic objets on the number of stars the results for 
space density may still be modified. 
