DIEECT EQUILIBBATION. 433 



whicli has its involved perturbations, that now increase and 

 now dec?ease, is lieie presented to us. Suppose a uew 

 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 residt ? 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 iacident force, falling on 

 the system from without, proved insufficient to overthrow it? 

 There would then arise a set of perturbations which would, 

 Lq 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 agaiu 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 estabhshed a set of planetary motions more 

 or less different from the preceding ones. All this would 

 necessarily follow from the truths that any new force brought 

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

 ia overcoming the forces that resist the divergence it gener- 

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

 posed, set up 1 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. K^ow though instead of being, like the Solar 

 System, in a state of independent moving equilibrium, 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 



