and on the Rotation of a Heavenly Body. 207 



Mercuiy . . . . •0 + '4= '4 



Venus •3-(_.4=: -7 



Earth -6 + -4= 1-0 



Mars 1-2 4- -4= 1-6 



Asteroids .... 2-4 + -4= 2*8 



Jupiter 4-8 + -4= 5*2 



Saturn 9-6 + •4=10-0 



Uranus 19-2 + -4=19-6 



Neptune .... 38-4 + •4 = 38-8 

 If we compare these numbers with the actual distances as set 

 down in the following Table, we shall see that there is a very 

 close agreement, with one exception, viz. that of Neptune : — 



Mean^ distance. Mass. 



Mercury .... -387 0-12 



Venus -723 0-88 



Earth 1-000 1-00 



Mars 1-523 0-13 



Ceres ..... 2-767 



Jupiter 5-202 338-45 



Saturn 9-538 101-03 



Uranus 19-183 14-78 



Neptune .... 30-2 24*57 



Here the continuity in the law of Bode, which assigns the 

 distances of all the other planets with such remarkable exactness, 

 ceases. Still, when we consider the infinite wisdom displayed by 

 the great Creator of the universe in the mechanism of our pla- 

 netary system — since it has been ascertained beyond doubt that 

 it is a system of wonderful stability and equilibrium, and that 

 there does not exist a single inequahty of any considerable 

 amount — that the masses of the planets seem to follow no law 

 whatever, but that the mean distances do follow a very remark- 

 able progression— is it not probable tliat there may yet be a law 

 almost, if not entirely, independent of the masses themselves, by 

 which the planets are linked together, and of which the law of 

 Eode is only an approximation ? The problem which I long ago 

 proposed to myself, is the following :— The limits of the solar 

 system being given, is it possible to assign the orbits of the in- 

 termediate i)lanets so that at any time they shall be least dis- 

 turbed ? To take a more simple case : suppose there were only 

 three planets, Mercury, Venus, and the Earth ; and supposing 

 Mercury and the Earth to move in elliptic orbits ; to assign the 

 orbit of Venus so that at any time she shall be least disturbed. 

 Since an undisturbed ])lanet describes an ellipse, it would seem 

 that Venus will be least disturbed wlien the path described is 

 most nearly elliptical. 



