416 Prof. E. Clausius on the Second Fundamental 



nicatiou with a second empty vessel ; a portion of the gas will 

 then pass info the empty vessel until the pressure in both ves- 

 sels has become equal. The gas has then expanded without 

 overcoming any external force; but we cannot restore it to its 

 former volume without the application of an external force. In 

 this case, therefore, the expansion of the gas has taken place in 

 an nnreversible manner. 



The final result of the expansion is in both cases so far the 

 same, that the disgregation of the gas has been increased to a 

 certain extent ; but in the one case, where a resistance had to 

 be overcome, heat was transformed into ergon, while in the 

 other case, where there was no resistance to overcome, no ergon 

 was done, and accordingly no heat was transformed into ergon. 

 If, on the other hand, it is required to compress the gas again 

 and so to diminish its disgregation, it is not possible to do this 

 otherwise than in such away that ergon is transformed into heat. 

 But since the transformation of ergon into heat is a positive 

 transformation, and that of heat into ergon a negative transfor- 

 mation, the above result may be expressed as follows : — A dimi- 

 nution of disgregation, which is a negative transformation, can- 

 not take place without a simultaneous positive transformation ; 

 while it is possible, on the contrary, for an increase of disgrega- 

 tion, which is a positive transformation, to take place without a 

 negative transformation. 



Let us now consider the second kind of transformation, or the 

 transformation of heat into ergon, cr vice versa, in relation to 

 the same point. 



In order that heat may be transformed into ergon, it is neces- 

 sary, as we have already seen, that either an increase of disgre- 

 gation should take place, or if this does not occur, as in the case 

 of cyclical processes, a certain further quantity of heat must be 

 transferred from a hotter to a colder body. But since increase 

 of disgregation and passage of heat from a hotter to a colder 

 body are positive transformations, it follows that the negative 

 transformation of heat into work is necessarily connected with a 

 simultaneous positive transformation. 



On the other hand, the positive transformation of ergon into 

 heat can quite well take place without any simultaneous nega- 

 tive transformation. "When, for example, force is expended in 

 overcoming the resistance of friction, heat is produced, and thus 

 ergon is transformed into heat without its being at all needful 

 that any negative transformation should take part in the pro- 

 cess. In like manner, the resistance of the air and the resist- 

 ance to conduction which an electric current has to overcome 

 in a conductor comport themselves in the same way as the re- 

 sistance of friction. 



