508 EQUILIBRATION. 



which these calculations proceed, and no consequent error in 

 the inferred rate at which the Sun is expending his reserve 

 of force, militates against the general proposition that this 

 reserve of force is being expended ; and must in time be ex- 

 hausted. Though the residue of undiffused motion in the 

 Sun, may be much greater than is above concluded ; though 

 the rate of radiation cannot, as assumed, continue at a uni- 

 form rate, but must eventually go on with slowly-decreasing 

 rapidity; and though the period at which the Sun will cease 

 to afford us adequate light and heat, is very possibly far more 

 distant than above implied; yet such a period must some 

 time be reached, and this is all which it here concerns us to 

 observe. 



Thus while the Solar System, if evolved from diffused 

 matter, has illustrated the law of equilibration in the estab- 

 lishment of a complete moving equilibrium ; and while, as at 

 present constituted, it illustrates the law of equilibration in 

 the balancing of all its movements; it also illustrates this law 

 in the processes which astronomers and physicists infer are 

 still going on. That motion of masses produced during Evo- 

 lution, is being slowly re-diffused in molecular motion of the 

 ethereal medium; both through the progressive integration 

 of each mass, and the resistance to its motion through space. 

 Infinitely remote as may be the state when all the motions of 

 masses shall be transformed into molecular motion, and all 

 the molecular motion equilibrated ; yet such a state of com- 

 plete integration and complete equilibration, is that towards 

 which thp changes now going on throughout the Solar Sys- 

 tem inevitably tend. 



§ 172. A spherical figure is the one which can alone 

 equilibrate the forces of mutually-gravitating atoms. If the 

 aggregate of such atoms has a rotatory motion, the form of 

 equilibrium becomes a spheroid of greater or less oblateness, 

 according to the rate of rotation ; and it has been ascertained 

 that the Earth is an oblate spheroid, diverging just as much 



