300 COSMIC PHILOSOPHY. [it. 11. 



transformed into heat. But if all the molar momentum thus 

 dissipated could be retained, the rhythmic motion of the 

 pendulum would continue for ever. But why ? Simply 

 because the momentum acquired during the descending 

 rhythm cannot cease to manifest itself, save as it is neu- 

 tralized during the ascending rhythm. And to adduce this 

 reason is to appeal directly to the persistence of force. 



The case of undulatory motions propagated among the 

 molecules of matter, is precisely similar. The passage of 

 an undulation implies at each instant a momentary local 

 rarefaction, followed by a momentary local condensation. 

 At a given instant certain molecules are removed further 

 from each other, while at the next succeeding instant they 

 approach each other, and the molecules immediately adjacent 

 are removed from each other. Why is rarefaction thus suc- 

 ceeded by condensation ? What is it that determines the 

 rebound of the disturbed molecule towards its original posi- 

 tion ? Obviously the progress of a pair of molecules toward 

 positions farther and farther from each other is opposed by 

 the inertia of adjacent molecules, which these push before 

 them as they advance. The local rarefaction is achieved 

 only at the expense of an adjacent condensation. This 

 condensation of the adjacent molecules increases their elas- 

 ticity until it begins to overbalance the momentum of the 

 separating pair of molecules, and then these molecules are 

 driven back toward each other. And so on, without inter- 

 mission. Now the recoil of the advancing molecule is 

 necessitated by the fact that the elasticity which it generates 

 in the resisting molecule cannot expend itself without pro- 

 ducing motion. And to say this is to recur again to our 

 fundamental axiom. 



Thus in all cases, whether molar or molecular, the rhythm 

 of motion is necessitated by the fact that in a multiform 

 universe no portion of matter can move uninfluenced by 

 some other portion. The illustrations just given do but 



