EQUILIBRATION. 503 



ances to change in that direction : leaving behind only those 

 movements which compensate each other, and so form a 

 moving equilibrium. Respecting the structural 



state simultaneously reached, it must obviously be one pre- 

 senting an arrangement of forces that counterbalance all 

 the forces to which the aggregate is subject. So long as 

 there remains a residual force in any direction be it excess 

 of a force exercised by the aggregate on its environment, or 

 of a force exercised by its environment on the aggregate, 

 equilibrium does not exist ; and therefore the re-distribution 

 of matter must continue. Whence it follows that the limit 

 of heterogeneity towards which every aggregate progresses, 

 is the formation of as many specializations and combina- 

 tions of parts, as there are specialized and combined forces 

 to be met. 



171. Those successively changed forms which, if the 

 nebular hypothesis be granted, must have arisen during 

 the evolution of the Solar System, were so many transitional 

 kinds of moving equilibrium ; severally giving place to more 

 permanent kinds on the way towards complete equilibration. 

 Thus the assumption of an oblate spheroidal figure by con- 

 densing nebulous matter, was the assumption of a temporary 

 and partial moving equilibrium among the component parts 

 a moving equilibrium that must have slowly grown 

 more settled, as local conflicting movements were dis- 

 sipated. In the formation and detachment of the 

 nebulous rings, which, according to this hypothesis, from 

 time to time took place, we have instances of progressive 

 equilibration ending in the establishment of a complete mov- 

 ing equilibrium. For the genesis of each such ring, implies 

 a perfect balancing of that aggregative force which the 

 whole spheroid exercises on its equatorial portion, by that 

 centrifugal force which the equatorial portion has acquired 

 during previous concentration: so long as these two forces 

 are not equal, the equatorial portion follows the contracting 



