116 NOMOS. 



tricities of not be accounted for in the same manner 



the planets , , . , . . n , , , 



are to be ac. as the orbital eccentricity of the Earth. 

 for ' At any rate there is no reason why the 

 needful differences of surface may not be assumed to 

 exist in all the planets, and there is some reason 

 to the contrary. Mercury is too much hid in the 

 light of the Sun to allow anything to be known 

 about the nature of his surface; and of Venus 

 nothing is really known except that she is invested 

 with a very dense atmosphere. In Mars the telescope 

 reveals unequivocally well-defined marks upon the 

 surface, which, from their constancy, can only be 

 accounted for by supposing them to be continents 

 and seas: it also reveals fainter and fleeting marks 

 which sometimes obscure the outline of the other 

 marks, and which are properly regarded as clouds. 

 The polar regions of the planet are also seen to be 

 covered with well-defined circular spots of dazzling 

 whiteness, which decrease in size as the summer 

 advances, and which, on that account, are most 

 probably the snows which have accumulated during 

 the long winter. Nothing is known about the 

 surfaces of the planetoids, and little, if anything, 

 about the surfaces of the large planets beyond the 

 planetoids. The belts of Jupiter are very remarkable 

 and familiar objects, but they are nothing more than 

 markings which indicate the presence of currents in 

 the atmosphere of the planet analogous to the trade- 

 winds of the Earth. They are nothing more than 

 this, because they exhibit changes of form which are 

 inconsistent with the idea that they have any more 

 fixed foundation than heavy clouds. The same may 



