APPENDIX A. 225 



living force, or, which is the same thing, of motive 

 power, if the bodies act upon each other without 

 directly touching each other, without actual col- 

 lision. Now everything leads us to believe that 

 the molecules of bodies are always separated from 

 each other by some space, that they are never ac- 

 tually in contact. If they touched each other, 

 they would remain united, and consequently 

 change form. 



If the molecules of bodies are never in close con- 

 tact with each other whatever may be the forces 

 which separate or attract them, there can never 

 be either production or loss of motive power in 

 nature. This power must be as unchangeable in 

 quantity as matter. Then the direct re-establish- 

 ment of equilibrium of the caloric, and its re-estab- 

 lishment with production of motive power, would 

 be essentially different from each other. 



Heat is simply motive power, or rather motion 

 which has changed form. It is a movement among 

 the particles of bodies. Wherever there is destruc- 

 tion of motive power there is, at the same time, 

 production of heat in quantity exactly proportional 

 to the quantity of motive power destroyed. Ke- 

 ciprocally, wherever there is destruction of heat, 

 there is production of motive power. 



