66 



from a distance perhaps ten times more remote, may 

 there not be another planet whose movement may approach 

 nearer that of the comets than Saturn? And may there 

 not be still others which, by an approximation of their 

 determinations through a series of gradations, transform 

 the planets gradually into comets, and connect the latter 

 with the former? 



The law according to which the eccentricity of the orbits 

 of the planets are in the inverse ratio of their distance from 

 the sun, supports this conjecture. The eccentricity in the 

 movements of the planets, increases with their distance 

 from the sun; and the more remote planets thus come 

 nearer the definition of comets. It may therefore be 

 supposed that there are other planets beyond Saturn 

 which are still more eccentric in their orbits, and thereby 

 have nearer affinity to comets, so that through a con- 

 tinuous gradation the planets finally become comets. 

 The eccentricity in the case of Venus is T |^ of the semi- 

 axis of its elliptical orbit; in the case of the Earth it is 

 ^g- ; in the case of Jupiter -% ; in the case of Saturn T V 

 of their respective semi-axes. The eccentricity therefore 

 evidently increases with the distances. It is true that 

 Mercury and Mars form exceptions to this law, on account 

 of their much greater eccentricity than their actual distance 

 from the sun would give ; but we shall learn in the sequel 

 that the same causes which explain why some planets 

 obtained a smaller mass when they were formed, account 

 for the deficiency of the impulsion required for a circular 

 orbit, and consequently have produced their eccentricity ; 

 and in both respects this has left them incomplete. 



Is it therefore not probable that the decrease of the eccen- 

 tricity of the heavenly bodies situated next beyond Saturn, 



