THE PLANETS. 423 



of small planets situated in the solar system between the orbits 

 of Mars and Jupiter, but on the whole nearer to the former, 

 is considered as a separating zone, as it were an inter- 

 mediate group; then, as has already been remarked, those 

 planets which are nearest to the sun, the interior (Mercury, 

 Venus, the Earth, and Mars) present several resemblances 

 among each other, and contrasts with the exterior planets 

 (Jupiter, Saturn, Uranus, and Neptune), or those which are 

 more remote from the sun, beyond this separating zone. 

 Of these three groups, the intermediate one occupies a space 

 scarcely equal to half the distance of the orbit of Mars from 

 that of Jupiter. Of the space between the two great princi- 

 pal planets, Mars and Jupiter, that part which is nearest to 

 Mars is, as far as has hitherto been observed, the most closely 

 filled; for if, in the zone which the asteroids occupy, the two 

 outermost, Flora and Hygeia, are examined, it will be found 

 that Jupiter is more than three times further from Hygeia 

 than Flora is from Mars. The most distinctive features of 

 this intermediate group of planets, are the great inclination 

 and eccentricity of their interlacing orbits ; and the extreme 

 smallness of the planets. The inclination of the orbits to- 

 wards the ecliptic increases in that of Juno to 13 3', in that 

 of Hebe even to 14 47', of Egeria to 16 33', of Pallas 

 even to 34 37' : while in the same intermediate group, 

 it falls as low, in the orbit of Astrea, as 5 19', in that 

 of Parthenope to 4 37', and that of Hygeia to 3 47'. The 

 whole of the orbits of the small planets having inclinations 

 smaller than 7, are, to go from the large to the small, those 

 of Flora, Metis, Iris, Astrea, Parthenope, and Hygeia. 

 Nevertheless, none of these orbits attain such a small degree 

 of inclination as those of Venus, Saturn, Mars, Neptune, 

 Jupiter, and Uranus. The eccentricities partly exceed even 

 that of Mercury (0'206); for Juno, Pallas, Iris, and Victoria 

 have 0-255, 0*239, 0'232, and 0-218; while Ceres (0-076) 



