340 SPECIAL RESULTS IN THE URANOLOGICAL 



solar domain is so unequal, that whilst, on the whole, the 

 proportion of the primary planets which have no such 

 attendants to those which are so accompanied is as 3 to 5, 

 the latter class, with the single exception of the Earth, 'all 

 belong to the outer planetary group, situated beyond the 

 intersecting orbits of the asteroids or small planets. The 

 only satellite in the group of the inner planets situated be- 

 tween the Sun and the asteroids viz. our Moon is strik- 

 ingly large in proportion to the diameter of its primary 

 planet. This proportion is T Jy; whereas the largest of 

 all the satellites of Saturn (the 6th, Titan) is probably 

 only -j-^.-j- , and the largest of Jupiter's satellites (the 

 3d) 2 S \T of their respective primaries. We must distinguish 

 in this consideration between relative and absolute magni- 

 tude. Our Moon, which is relatively so large, is abso- 

 lutely smaller than any of the four satellites of Jupiter ; the 

 diameter of the former being 454, and the diameters of the 

 latter respectively 776, 664, 529, and 475 German geogra- 

 phical miles (or the Moon 1816, and Jupiter's satellites 

 3104, 2656, 2116, and 1900 English geographical miles). 

 The magnitude of the 6th satellite of Saturn differs very 

 little from that of the planet Mars (the diameter of which 

 is 892 German, or 3568 English geographical miles) ( 54 ). 

 If the question of telescopic visibility depended solely on 

 the diameter of the satellite, and was not also conditional 

 on the proximity to the disk of its primary planet, and the 

 remoteness and nature of its light-reflecting surface, we 

 should have to regard the 1st and 2d of Saturn's satellites 

 (Mimas and Enceladus), and two of the satellites of Uranus, 

 which have been repeatedly seen, as the smallest of 



