88 THE PHYSICAL SIGNIFICANCE OF ENTROPY 



divided by the temperature (in centigrade degrees). In English 

 units and the F.P.S. system this numerical value is 5.50 (io~ 24 ). 

 From the whole development we see that entropy 5 depends 

 only on the number of complexions; it should not be considered, 

 as is sometimes done, as of the same dimensions of energy or 

 anything that may generally be called a factor of energy. 



SECTION D 

 THE SECOND LAW 



It is evident that all these results have for their original basis 

 the Theory of Probabilities. Consequently, because these con- 

 clusions are thus based, they must be interpreted according to the 

 general method underlying this Theory. This method essentially 

 is the determination of average (mean) values and calling them 

 the probable ones. We therefore conclude that each state is 

 characterized by the mean number of complexions belonging 

 to that state, that is, by this mean number which changes always 

 in a one-sided way, ever in the same sense, inasmuch as it inevitably 

 and invariably grows till the normal, settled condition is reached. 



For the sake of clarity we must keep in mind that the motions 

 of the individual atoms are reversible and that in this sense the 

 irreversible processes are reduced to reversible ones. But the 

 process as a whole is not reversible because, by the very act of 

 complete reversal, we would suspend the general, chaotic character 

 of the elementary motions and give them to this extent a special, 

 prearranged feature which would be more or less hostile to the 

 original definition of " elementary chaos." The irreversibility 

 is not in the elementary events themselves, but solely in their 

 irregular arrangement. It is this which guarantees the one-sided 

 change of the mean value characteristic of each one of the successive 

 states of the process. 



Now remembering that the kernel of the Second Law is that 

 all processes in Nature are irreversible, or, that all changes in 



