PHILOSOPHICAL SOCIETY OF WASHINGTON. 153 



under this dynasty of percussion, do not speedily raise the tempera- 

 ture of all coherent bodies to a fierce and glowing heat?* 



And this brings us face to face with the great radical — incom- 

 mensurable difference between " force " and energy, — that the func- 

 tion of the former is attended with no expenditure, and is capable 

 of no exhaustion. The truth of this bold asseveration has been 

 tested again and again by every expedient which the most skillful 

 and ingenious kinematists have been able to devise for its question, 

 without the suspicion of impeachment ; and it remains to-day, one 

 of our strongest and best assured inductions. 



On this broad platform rests the issue between kinematism and 

 dynamism, — that the former inevitably contravenes and destroys 

 that bulwark of modern physics — the conservation of energy ; while 

 the latter is its only support and its necessary foundation. With- 

 out the indestructible — unwasting — tensions of molecular attraction 

 and repulsion, it lies beyond the scope of human ingenuity to devise 

 or imagine a conservative system. 



The fundamental — the inherent and incurable weakness of every 

 attempt to supersede " force " by motion is betrayed in this, — the 

 inadmissible supposition of a world held together only by the infi- 

 nite expenditure of work, for whose existence no provision is devised, 

 and for whose maintenance no motor can be suggested or conceived.^ 



* Eeferring to the steady maintenance of material tensions by supposed 

 setherial motions or vortices, J. Clerk Maxwell truly remarks: "No 

 theory of the constitution of the ether has yet been invented which will 

 account for such a system of molecular vortices being maintained for an in- 

 definite time without their energy being gradually dissipated into that irreg- 

 ular agitation of the medium which in ordinary media is called heat." 

 (Encyclopcedia Britannica. 9th ed. 1878: art. "Ether:" vol. vni, p. 572.) 



f "Taking such a system in its entirety (where force exists not), there is 

 no possibility of its reproduction. There is therefore a necessary and un- 

 ceasing drain on the vis viva of such a system. Everything which consti- 

 tutes an event, whatever its nature, exhausts some portion of the original 

 stock. Such a system has no vitality. It feeds upon itself and has no 

 restorative power." Sir John Herschel, ("On the origin of Force." — 

 Fortnightly Review. July 1, 1865: vol. I, p. 437. And. Familiar Lectures, 

 [etc.] 1866: art. XII, p. 465.) 



"It is remarkable" observes J. Clerk Maxwell, " that of the three 

 hypotheses which go some way toward a physical explanation of gravitation, 

 every one involves a constant expenditure of work." (Encyclopced. Brit. 

 9th ed. 1875: art. "Attraction:" vol. Ill, p. 65.) 



