DIRECT EQUILIBRATION. 433 



which has its involved perturbations, that now increase and 

 now decrease, is heie presented to us. Suppose a new 

 force were brought to bear on this moving equilibrium — say 

 by the arrival of some wandering mass, or by an additional 

 momentum given to one of the existing masses — what would 

 be the result ? If the strange body or the extra force were 

 very large, it might so derange the entire system as to cause 

 its collapse : by overthrow of its rhythmical movements, the 

 moving equilibrium might rapidly be changed into a com- 

 plete equilibrium. But what if the incident force, falling on 

 the system from without, proved insufficient to overthrow it? 

 There would then arise a set of perturbations which would, 

 in the course of an enormous period, slowly work round into 

 a modified moving equilibrium. The effects primarily im- 

 pressed on the adjacent masses, and in a smaller degree on 

 the remoter masses, would soon become complicated with the 

 secondary effects impressed by the disturbed masses on one 

 another ; and these again with tertiary effects. Waves of 

 perturbation would continue to be propagated throughout 

 the entire system; until, around a new centre of gravity, 

 there had been established a set of planetary motions more 

 or less different from the preceding ones. All this would 

 necessarily follow from the truth^ that any new force brought 

 to bear on a moving equilibrium, must gradually be used up 

 in overcoming the forces that resist the divergence it gener- 

 ates : which antagonizing forces, being then no longer op- 

 posed, set up a counter-action, ending in a compensating 

 divergence in the opposite direction, that is followed by a 

 re- compensating divergence ; and so on, until there is either 

 established some additional rhythmical movement, or some 

 equivalent modification of the pre-existing rhythmical move- 

 ments. ]STow though instead of being, like the Solar 

 System, in a state of independent moving equilibrimn, an 

 organism is in a state of dependent moving equilibrium 

 {First Principles, § 130) ; yet this does not prevent the 

 manifestation of the same law. Every animal daily obtains 



