306 SPECIAL RESULTS IN THE URANOLOGICAL 



0.076, 0.0&6, 0.089, being excentricities inferior to that 

 of the orbit of Mars (0,093), but without making so near 

 an approach to a circular orbit as the planets Jupiter, Sa- 

 turn, and Uranus. The diameters of the telescopic planets 

 are so small as to render their measurement very difficult 

 and uncertain. From the observations of Lamont at Munich, 

 and of Madler with the Dorpat refractor, it is probable that 

 the largest of them all does not exceed at the utmost 145 

 German, or 580 English geographical miles, being ^tli of 

 the diameter of Mercury, and -^th of that of the Earth. 



If we call the four planets nearest to the Sun, between 

 the ring of Asteroids or small planets and the central 

 body, inner planets, and the four planets which are fur- 

 thest from the sun (being placed between the ring of 

 the asteroids and the unknown extremities of the solar 

 domain) outer planets, we find the inner planets all of 

 moderate magnitude, comparatively dense, slow in their 

 movements of rotation round their axes, (the periods being 

 nearly similar in all, differing little in any case from 24 

 hours), and, with the exception of the Earth, wholly desti- 

 tute of satellites. The four outer planets, Jupiter, Sa- 

 turn, Uranus, and Neptune, on the other hand, are much 

 larger, five times less dense, rotate twice as rapidly round their 

 axes, are more flattened at the poles, and richer in satellites 

 in the average proportion of 20 to 1. Of the four inner 

 planets the Earth is the largest (the diameters of Mercury 

 and Mars are respectively -f-ths and J of the Earth's 

 diameter) ; while the outer planets, on the other hand, are 

 from 4'2 to 11*2 times larger than the Earth. The density 

 of the Earth being taken as unity, the densities of Venus 

 and Mars agree with it to less than T Vth, and the density 



