PORTION OF THE COSMOS. COMETS. 395 



fancies, based on mistaken analogies respecting a supposed 

 law of increasing excentricity, magnitude, and rarity of 

 matter in planetary bodies with increasing solar distances, 

 led to the view, that beyond Saturn there would be disco- 

 vered excentric planetary cosmical forms of enormous 

 volume, "constituting intermediate links or gradations 

 between planets and comets; and that the last or outer- 

 most planet might even deserve to be called a comet, because 

 it might perhaps be found to intersect the orbit of the pre- 

 ceding planet nearest to itself, i. e. Saturn" ( 645 ). Such a view 

 of the graduated succession of forms in the structure of the 

 Universe, analogous to the often misused doctrine of gra- 

 dation or transition of form in organic existence, was shared 

 by Kant, one of the greatest intellects of the eighteeenth 

 century. Eespectively twenty-six and ninety-one years after 

 the dedication to Frederick the Great of the Naturgeschichte 

 des Himmels by the Konigsberg philosopher, Uranus and 

 Neptune were discovered by William Herschel and Galle; 

 but both these planets have a less excentricity than Saturn ; 

 indeed, while the excentricity of Saturn is 0'056, that of 

 the outermost of all the planets now known to us, Neptune, 

 is 0*008, nearly the same as that of Yenus, so near to the 

 Sun (O'OOG). In other respects, also, neither Uranus nor 

 Neptune show anything of the anticipated cometary qualities. 

 As within a recent period, (since ] 81 9), the discovery of 

 five interior comets have followed that of Encke's, the whole 

 six forming apparently a distinct group, whose semi-major 

 axis does not differ much from that of the majority of the 

 small planets, the question has been suggested, whether the 

 group of the interior comets may not have originally consti- 

 tuted a single cosmical body, as in the case of the small 



