PREFACE 



IN this little book the author has in the main sought to present 

 the interpretation reached by BOLTZMANN and by PLANCK. The 

 writer has drawn most heavily upon PLANCK, for he is at once 

 the clearest expositor of BOLTZMANN and an original and important 

 contributor. Now these two investigators reach the result that 

 entropy of any physical state is the logarithm of the probability 

 of the state, and this probability is identical with the number 

 of "complexions" of the state. This number is the measure of 

 the permutability of certain elements of the state and in this sense 

 entropy is the "measure of the disorder of the motions of a system 

 of mass points." To realize more fully the ultimate nature of 

 entropy, the writer has, in the light of these definitions, interpreted 

 some well-known and much-discussed thermodynamic occurrences 

 and statements. A brief outline of the general procedure followed 

 will be found on p. 3, while a fuller synopsis is of course given 

 in the accompanying table of contents. 



J. F. KLEIN. 



LEHIGH UNIVERSITY, October, 1910. 



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