110 NOMOS. 



We may assume, then, without further preamble 

 for it is not necessary to repeat the explanation 

 already given that the reactions between the solar 

 and terrestrial currents will cause the earth to move 

 in a circular orbit around the sun, if she 

 the e iabora- nas to encounter the requisite amount of 



res i stance - ^ s ^ e nas to encounter the 

 medium in requisite amount of resistance, we sav ; 



space. /. ' 



for it the ever-acting impulse was not 

 counteracted in this manner, the earth must go on 

 moving with continually increasing velocity away 

 from the skirts of any orbit. In a word, that resist- 

 ing medium is requisite which is demanded by the 

 previous considerations respecting law, and which 

 appears to be revealed by the retarded movements 

 of Encke's comet. Now what the amount of the 

 impulse may be, and what the amount of resistance, 

 we have not yet the means of knowing ; but, whether 

 great or small, it is plain that each must be adjusted 

 to the other so as to allow the amount of motion 

 which is required. Comparing by time, for example, 

 the impulse which has acted upon the earth during 

 a single second must be entirely exhausted by the 

 resistance when the earth has travelled through 

 101,066 feet, so that no spare velocity remains to be 

 carried over into the next second. We may argue, 

 however, that the resistance is very slight and the 

 impulse comparatively feeble, for comets which must 

 be denser than the medium in which they move are 

 of such exceeding rarity that the smallest star may 

 be seen through their very nucleus without any 

 obscuration of its lustre, and because they have 



