534 COSMOS. 



the planet next to it." 1 Such an opinion of the connection 

 of forms in the universe, analogous to the frequently mis- 

 employed doctrine of transition in organic nature, was shared 

 by Immanuel Kant, one of the greatest minds of the eighteenth 

 century. At two epochs, twenty-six and ninety-one yearp 

 after the Naturgeschichte des Himmels was dedicated to the 

 rreat Frederick by the Konigsberg philosopher, Uranus and 

 Neptune were discovered by William Herschel and Galie ; 

 but the orbits of both planets have a less degree of excen- 

 tricity than that of Saturn ; if even the latter is 0-056, so 

 on the contrary Neptune, the outermost of all known planets, 

 moves in an orbit whose excentricity is 0-008, nearly the 

 same as that of Venus (0-006). In addition to this, Uranus 

 and Neptune present none of the predicted cometary cha- 

 racters. 



As in more recent times (since 1819), the discovery of 

 Encke s Comet was gradually followed by those of five inte- 

 rior comets, forming as it were a peculiar group, the semi- 



1 " By means of a series of intermediate members," savs 

 Immanuel Kant, "the last planets beyond Saturn would gra- 

 dually pass into comets, and so the last species would be 

 connected with the first. The law according to which the 

 excentricity of the planetary orbits is proportionate to the 

 distances of the planets from the Sun, supports this conjecture. 

 The excentricity increases with the distance, and consequently 

 the more distant planets approach nearer to the definition of 

 comets. The last planet and the first comet may be called 

 that body which in its perihelion intersects the orbit of the 

 adjoining planet, perhaps that of Saturn. Our theory of the 

 mechanical formation of the cosmical bodies is al.^o clearly 

 proved by the magnitudes of the planetary masses which 

 increase with the distance from the Sun.'" Kant, Natur- 

 gescliichte des Himmels (1755), in his B'dmmtliclie Werke, 

 Th. vi. pp. 88 and 195. At the commencement of the filth 

 section (p. 131), he speaks of the former cometary nalure 

 which Saturn was supposed to have possessed. 



