388 POPULAR SCIENCE MONTHLY. 



the southern, Gould's 'Uranometria Argentina.' A zone from the equator 

 to 30° south declination is common to both; for this zone I use Gould. 

 The number of each class in the entire sky, north and south of the 

 celestial equator, is as follows: 



Northern Southern 

 Hemisphere. Hemisphere. 



Pickering. Gould. Total. 



1+ 9 14 23 



2.0 17 15 32 



2.5 17 24 41 



3.0 37 41 78 



3.5 61 74 135 



4.0 114 126 240 



4.5 228 234 462 



5.0 450 426 876 



5.5 787 681 1,468 



6.0 789 1,189 1,978 



Sum. 2,509 2,824 5,333 



It would seem from this that the number of lucid stars in the south- 

 ern celestial hemisphere is 315 greater than in the northern. But this 

 arises wholly from a seemingly greater number of stars of magnitude 6. 

 In the zone 0° to 30° S., Pickering has 214 stars of this class fewer than 

 Gould. Hence it is not likely that there is any really greater richness 

 of the southern sky. 



The total number of lucid stars is thus found to be 5,333. But it is 

 not likely that stars of magnitudes 6.1 and 6.2 should be included in this 

 class, though this is done in the above table. From a careful study and 

 comparison of the same data from Pickering and Gould, Sehiaparelli 

 enumerated the stars to magnitude 6.0. He found: 



North pole to 30° S 3,113 stars. 



30° S. to south pole 1,190 " 



Total lucid stars 4,303 



For most purposes a classification by entire magnitudes is more in- 

 structive than one by half magnitudes. From the third magnitude 

 downward we may assume that 40 per cent, of the stars of each half 

 magnitude belong to the magnitude next above, and 60 per cent, to that 



next below. We thus find that of 



Total. 



Mag. and 1 there are 21 stars 21 



Mag. 2 there are 52 stars 73 



Mag. 3 there are 157 stars 230 



Mag. 4 there are 506 stars 736 



Mag. 5 there are 1,740 stars 2,476 



Mag. 6 there are 5,171 stars 7,647 



