318 POPULAB SCIENCE MONTHLY. 



The numbers on the planisphere given in each area thus express the 

 star density of the region, or the number of stars per 100 square de- 

 grees, expressed generally to the nearest unit, the half unit being some- 

 times added. 



A study of the reproduction which we give will show how fairly 

 well the Milky Way may be traced out round the sky by the tendency 

 of those stars visible to the naked eye to agglomerate near its course. 

 In other words, were the cloud forms which make up the Milky Way 

 invisible to us, we should still be able to mark out its course by the 

 condensation of the stars. As a matter of interest, I have traced out 

 the central line of the shaded portions of the planispheres as if they 

 were the galaxy itself. The nearest great circle to the course of this line 

 was then found to have its pole in the following position: 



E. A.; 12h. 18m. 



Dec. + 27°. 



This estimate was made without having at the time any recollection 

 of the position of the galaxy given by other authorities. Compared 

 with the positions given in the last chapter by Gould and Seeliger, it 

 will be seen that the deviation is only 5° in right ascension, while the 

 declinations are almost exactly similar. We infer that the circle of con- 

 densation found in this way makes an angle with the galaxy of less 

 than 5°. 



DISTRIBUTION OF THE FAINTER STAES. 



The most thorough study of the distribution of the great mass of 

 stars relative to the galactic plane has been made by Seeliger in a series 

 of papers presented to the Munich Academy from 1884 to 1898. The 

 data on which they are based are the following: 



1. The Bonner Durchmusterung of Argelander and Schonfeld, de- 

 scribed in our third chapter. These two works included under this title 

 are supposed to include all the stars to the ninth magnitude, from the 

 north pole to 24° of south declination. But there are some inconsisten- 

 cies in the limit of magnitude which we shall hereafter mention. 



2. The 'star gauges' of the two Herschels. These consisted simply 

 in counts of the number of stars visible in the field of view of the tele- 

 scope when the latter was directed toward various regions of the sky. 

 Sir William Herschel's gauges were partly published in the 'Philosophi- 

 cal Transactions.' A number of unpublished ones were found among 

 his papers by Holden and printed in the publications of the Washburn 

 Observatory, Vol. II. The younger Herschel, during his expedition to 

 the Cape of Good Hope, continued the work in those southern regions 

 of the sky which could not be seen in England. 



3. A count of the stars by Celoria, of Milan, in a zone from the 

 equator to 6° Dec, extended round the heavens. 



