26 INVAEIABLE PLANE. [SECT. in. 



contains no principle of decay, unless a rotatory motion from 

 west to east has been given to this fluid by the bodies of the 

 solar system, which have all been revolving about the sun in 

 that direction for unknown ages. This rotation, which seems 

 to be highly probable, may even have been coeval with its 

 creation. Such a vortex would have no effect on bodies 

 moving with it, but it would influence the motions of those 

 revolving in a contrary direction. It is possible that the 

 disturbances experienced by comets which have already re- 

 vealed the existence of this fluid may also, in time, disclose 

 its rotatory motion. 



The form and position of the planetary orbits, and the 

 motion of the bodies in the same direction, together with the 

 periodicity of the terms in which the inequalities are ex- 

 pressed, assure us that the variations of the system are con- 

 fined within very narrow limits, and that, although we do not 

 know the extent of the limits, nor the period of that grand 

 cycle which probably embraces millions of years, yet they 

 never will exceed what is requisite for the stability and har- 

 mony of the whole; for the preservation of which every cir- 

 cumstance is so beautifully and wonderfully adapted. 



The plane of the ecliptic itself, though assumed to be 

 fixed at a given epoch for the convenience of astronomical 

 computation, is subject to a minute secular variation of 

 45" *7, occasioned by the reciprocal action of the planets. 

 But, as this is also periodical, and cannot exceed 2 42', 

 the terrestrial equator, which is inclined to it at an angle of 

 23 27' 34"-69, will never coincide with the plane of the 

 ecliptic : so there never can be perpetual spring (N. 79). 

 The rotation of the earth is uniform ; therefore day and 

 night, summer and winter, will continue their vicissitudes 

 while the system endures, or is undisturbed by foreign 

 causes. 



Yonder starry sphere 

 Of planets and of fix 'd, in all her wheels, 

 Resembles nearest mazes intricate, 

 Eccentric, intervolved, yet regular, 

 Then most, when most irregular they seem. 



