ZONE OF PLANETS BETWEEN MARS AND JUPITER. 95 



as we have actually discovered between Mars and Ju- 

 pitec, 



"With regard to the actual number of bodies belonging 

 to this zone of planets, we can do little more than con- 

 jecture. Already we have one asteroid of the sixth 

 magnitude, one of the seventh, five of the eighth, nineteen 

 of the ninth, and fourteen of the tenth or eleventh. 

 It would require 400 bodies as large as the largest of 

 the asteroids to make a body one fourth of the size of the 

 earth ; and, according to Le Yerrier, the sum of all the 

 asteroids can not exceed this limit. When we consider 

 the shortness of the period during which stars below the 

 eighth magnitude have been systematically observed, we 

 see room for the discovery of several more planets of the 

 ninth magnitude, and perhaps three or four hundred more 

 of inferior dimensions. 



