OF THE COSMOS. NUMBER OF THE FIXED STARS. 89 



the conjectures which, founded on the "star-gaugings" of 

 particular parts of the Milky Way, touch the theoretical 

 solution of the question How many stars would be distin- 

 guished over the whole heavens by Herschers 20 -foot 

 telescope, comprehending all those stars whose light is be- 

 lieved( 169 ) to have required 2000 years to reach the Earth? 

 The numerical data which I here publish on this subject 

 are chiefly taken from the final results obtained by my highly 

 esteemed friend Argelander, Director of the Astronomical 

 Observatory at Bonn. The author of the " Beview of the 

 Northern Heavens" has carefully examined for me afresh, 

 at my request, the data supplied by Star-catalogues up to 

 the present time. In the lowest class of stars visible to the 

 naked eye some uncertainty is occasioned by the difference 

 of estimation caused by organic differences in individual ob- 

 servers, stars between the 6th and 7th magnitudes being found 

 among those of the 6th magnitude. By a variety of com- 

 binations we obtain, as a mean number, from 5000 to 5800 

 as the number of stars visible to the unassisted eye, through- 

 out the entire heavens. The distribution of the fixed stars 

 in descending magnitudes down to the 9th, is given by 

 Argelander( 170 ) approximately as follows : 



1st magnitude. 2nd magnitude. 3rd magnitude. 4th magnitude. 5th magnitude. 



20 65 190 425 1100 



6th magnitude. 7th magnitude. 8th magnitude. 9th magnitude. 



3200 13000 40000 142000 



The number of stars which can be clearly distinguished by 

 the naked eye (4022 above the horizon of Berlin, 4638 

 above that of Alexandria), appears at first sight astonishingly 



