296 SPECIAL RESULTS IN THE URANOLOGICAL 



^X 



IL 



THE PLANETS. 



BEFORE we enter into descriptions of each of these bodies 

 viewed individually, I propose to present some general and 

 comparative considerations respecting the entire class to 

 which they belong. These considerations will embrace, in 

 conformity to the state of discovery at the present moment, 

 22 primary planets, and 21 subordinate bodies, moons or 

 satellites. They do not apply to other classes of bodies in 

 our planetary or solar system, among which comets whose 

 orbits have been calculated are already ten times as nume- 

 rous. Planets have, generally speaking, only a slight degree 

 of scintillation, because they shine by the solar light reflected 

 from their disks. (The difference in this respect between 

 disks and luminous points has been explained in pp. 68 and 

 xxviii. of the First Part of the present volume.) In the 

 pale radiance of the illuminated moon, and in the reddened 

 light of its darkened disk, which shows itself with peculiar 

 strength within the tropics, the solar light, as seen by the 

 observer stationed on the Earth, has suffered a two-fold 

 change of direction. That the Earth and other planets are 



