1 334 



value of tlie gradients between the 10^'' and the 13^'' magnitude. 

 A second explanation is the admittance of absorbing nebulons 

 masses. If snch nebulous matter should exist in I lie regions of the 

 galactic condensations, only the more distant stars would be dimmed, 

 and the phenomena would be the same as in the former case, a 

 relative excess of brilliant stars. From the numbers found, it there- 

 fore becomes evident, that the absorbing dark nebulous mass causing 

 the tipartite hole, is so near as to dim also the majority of the 

 stars of the 10''' and 11'^ magnitude. It stands in no organic con- 

 nection to the galactic clouds, being only accidentally projected against 

 that clear background. 



5. Comparison ivith other results. Our former in\'estigations ^; 

 stated for the galactic region in Aquila a strong increase of the 

 gradient up to far over 0,6. These results however cannot be imme- 

 diately compared with the present ones, another scale of magnitudes 

 having been used. The scale of Groningen Publ. J8 that was em- 

 j)loyed there, needs increasing corrections to reduce them to the 

 visual Harvard scale; in order to obtainthe photographic magnitudes, 

 belonging to log \, still inci-easing positive corrections have to be 

 added, as the average colour-index increases for the fainter stars. ') 

 With these corrections we gel : 



Here an increase of the gradient from the 13''' magnitude (phot.) 

 upward is perceptible: this therefore corresponds to the results now 

 obtained. But the \alues of the gradients now obtained are consi- 



1) Researches into the structure of the Galaxy. Proceedings R. A. S., Amster- 

 dam, June 25th 1910. 



-) P. J. VAK Rhun. Un the number of stars of each photographic magnitude. 

 Publ. Groningen W. 27. 



