28 INEQUALITY OF JUPITER AND SATURN. [SECT. in. 



mitted to their mutual attractions only, always maintains a 

 fixed position, whence the oscillations of the system may be 

 estimated through unlimited time. Future astronomers will 

 know, from its immutability or variation, whether the sun 

 and his attendants are connected or not with the other sys- 

 tems of the universe. Should there be no link between 

 them, it may be inferred, from the rotation of the sun, that 

 the centre of gravity (N. 82) of the system situate within 

 his mass describes a straight line in this invariable plane or 

 great equator of the solar system, which, unaffected by the 

 changes of time, will maintain its stability through endless 

 ages. But, if the fixed stars, comets, or any unknown and 

 unseen bodies, affect our sun and planets, the nodes of this 

 plane will slowly recede on the plane of that immense orbit 

 which the sun may describe about some most distant centre, 

 in a period which it transcends the power of man to deter- 

 mine. There is every reason to believe that this is the case ; 

 for it is more than probable that, remote as the fixed stars 

 are, they in some degree influence our system, and that even 

 the invariability of this plane is relative, only appearing fixed 

 to creatures incapable of estimating its minute and slow 

 changes during the small extent of time and space granted 

 to the human race. " The development of such changes," 

 as M. Poinsot justly observes, " is similar to an enormous 

 curve, of which we see so small an arc, that we imagine it 

 to be a straight line." If we raise our views to the whole 

 extent of the universe, and consider the stars, together with 

 the sun, to be wandering bodies, revolving about the common 

 centre of creation, we may then recognise in the equatorial 

 plane passing through the centre of gravity of the universe 

 the only instance of absolute and eternal repose. 



All the periodic and secular inequalities deduced from the 

 law of gravitation are so perfectly confirmed by observation, 

 that analysis has become one of the most certain means of 

 discovering the planetary irregularities, either when they 

 are too small, or too long in their periods, to be detected by 



