NOMOS. 115 



and less as the distance from the Sun increases. 

 Nay, analogy is in favour of this possibility ; for it 

 is not unnatural to assume that the arrangement 

 of the atmosphere of the earth may be that of the 

 atmosphere of atmospheres which fills the abyss. 

 And if this be the case, then we see a means of 

 escaping from the difficulty with which we are at 

 present concerned ; for if the resistance which the 

 planets have to encounter in their movements is 

 inversely proportionate to their distance from the 

 Sun, it follows that the actual motion of any planet 

 in its orbit cannot be taken as the measuVe of the 

 force which is concerned in producing thr^ motion. 

 Where the resistance is only slight, a smai- f amount 

 of force may serve to produce an amount c/ J motion 

 which would require a considerable exper ^iture of 

 force if the resistance were greater; and . us the 

 impulse which would only serve to send Neptune 

 through 26 feet in a second, if he had to overcome 

 the resistance which Mercury has to encounter, may 

 serve to send him through no less than 18,435 feet 

 in a second through the rare medium in which his 

 path is actually appointed. 



And thus, if we assume that space is filled with a 

 medium whose powers of resistance are inversely 

 proportionate to the distance from the Sun, the rate 

 at which the planets move is no objection to the idea 

 that these movements may be explained upon the 

 principles which have been employed in explaining 

 the movements of the Earth. 



Nor is there any reason why the or- HOW the par. 

 bital eccentricity of all the planets should 



I 2 



