ACTIVE POWERS. 405 



traverses annually, if multiplied by three thousand years, 

 during which we know 110 change has taken place, give 

 us 99,000,000,000 as the distance passed over in that 

 period. How wide, then, must have been the journey 

 of the system in space to produce the alteration in the 

 physical powers, by which these changes have been 

 effected ! 



We have an example, and a striking one, of the varia- 

 tions which may be produced in all the physical con- 

 ditions of a world, in those disturbances of Uranus which 

 led to the discovery of Neptune. For thirty years or 

 more certain perturbations Avere observed in this distant 

 planet, the discovery of Sir William Herschel, and 

 calculation pointed to some still more remote mass of 

 matter as the cause, which has been verified by its actual 

 discovery. But now Uranus is at rest ; quietly that 

 star progresses in its appointed orbit, Neptune can no 

 longer, for the present, cause it to move with greater or 

 less rapidity they are too remote to produce any sensible 

 influence upon each other. Consequently, for thirtyyears, 

 it is evident, phenomena must have occurred on the surface 

 of Uranus, which can be no longer repeated until these 

 two planets again arrive at the same positions in their 

 respective paths which they have occupied since 1812. 

 These considerations assist us in our attempts to com- 

 prehend infinite time and space ; but the human mind 

 fails to advance far in the great sublimity. 



Through every inch of space we have evidence of the 

 exercise of such forces as we have been considering. 

 Gravitation chains world to world, and holds them all 

 suspended from the mystic centre. Cohesion binds 

 every mass of matter into a sphere, while motion exerts 

 a constant power, which tends to alter the form of the 

 mass. The earth's form a flattened spheroid the 

 rings of Saturn and of Neptune are the consequences 

 of motion in antagonism to cohesion. Heat, radiating 

 from one planet to another, does its work in all, giving 



