ASTRONOMY 



example, a standard star of magnitude 2 is about 

 2 1 times as bright as a standard star of magnitude 3. 

 Returning now to the Franklin-Adams plates, 

 it was, of course, clearly impossible to count all 

 the stars which they showed, and therefore typical 

 areas were selected and the stars of different mag- 

 nitudes counted. The result of the counts thus 

 made by Chapman and Melotte are shown in the 

 accompanying table : 



THE NUMBERS OF STARS OF DIFFERENT MAGNITUDES 

 Magnitude Number 



I II 



1-2 27 



2 -3 ... 73 



3-4 189 



4-5 . 650 



5-6 .' . . . 2,200 



6-7 . ... 6,600 



7-8 . . 22,550 



8-9 . . 65,000 



9-!o . 174,000 



lo-n . . . 426,000 



I][ - 12 . . . 961,000 



12-1 3 . 2,020,000 



I 3~ I 4 . 3,960,000 



H-I5 . 7,820,000 



I 5~ 1 ^ . 14,040^000 



16-17 . . 25,400,000 



Although the faintest stars shown on the plates 

 are of the seventeenth magnitude, there must be 



49 



