98 THE PHYSICAL SIGNIFICANCE OF ENTROPY 



tion. For changes of the latter sort were never considered in 

 denning entropy." 



(15) " Finally, we may designate the sum of the entropies of 

 several bodies as the entropy of the system of all the bodies, 

 provided the system can be subdivided into infinitesimal elements 

 for which uniform density and temperature can be assumed; 

 but velocity and force of gravitation do not at all enter into the 

 expression for entropy." 



SECTION B 

 GENERAL CONCLUSION AS TO ENTROPY CHANGES 



Now that the existence and value of entropy have been estab- 

 lished for every state of any body, we can proceed to draw general 

 conclusions in much the same way as that followed with the ideal 

 gases. The general result is : 



" IT IS IN NO WAY POSSIBLE TO DIMINISH THE ENTROPY OF A 

 SYSTEM OF BODIES WITHOUT HAVING CHANGES REMAIN IN OTHER 

 BODIES." 



If we admit to the system all the bodies participating in the 

 process, this theorem becomes: 



" Every physical and chemical process occurring in Nature 

 takes place in such a way that there is an increase in the sum of 

 the entropies of the bodies in any way participating in the process" 



We will close with BOLTZMANN'S statement: 



" The driving motive (or impelling cause) in all natural events 

 is the difference between the existing entropy and its maximum 

 value" 



