2 THE PHYSICAL SIGNIFICANCE OF ENTROPY 



down to the bottom is worthy of all encouragement and respect. 

 For this reason and because the matter is of prune importance 

 to the technical world, the final .meaning of entropy (i.e., of the 

 Second Law) must be .clarified and realized. Indeed, we may well 

 go beyond this somewhat narrow view and say that this is well 

 worth doing because change of entropy constitutes the driving motive 

 in all natural events; it has therefore a reach and a universality 

 which even transcends that of the First Law, or Principle of the 

 Conservation of Energy. 



In striving to present the physical meaning of entropy and of the 

 Second Law, the writer cannot lay claim to any originality; he 

 has simply tried here to put in logical order the somewhat scattered 

 propositions of the leading investigators of this subject and in 

 such a way that the difficulties of apprehension might be minim- 

 ized; in other words, to present the solutions of his own diffi- 

 culties, in the hope that the solutions may be helpful to other 

 students of engineering and thermodynamics. In overcoming these 

 difficulties, the writer owes everything to the books and papers by 

 PLANCK and BOLTZMANN, pre-eminently to PLANCK, who has so 

 clearly and appreciatively interpreted the life work of BOLTZ- 

 MANN. 1 The writer furthermore wishes to say that he has not 

 hesitated here to quote verbatim from both these investigators 

 and not always so that their own statements can be distinguished 

 from his own. If any part of this presentation is particularly 

 clear and exact the reader will be safe in crediting it to one or 

 the other of these two investigators and expositors, although it 

 would not be right to consider them responsible for everything 

 contained in this little book. 



In considering the proper approach to the matter in hand we 

 must remember that 2 " in physical science there are two more or 



1 BOLTZMANN, GasTheorie; PLANCK, Thermodynamik, Theorie der Warme- 

 strahlung, and Acht Vorlesungen iiber Theoretische Physik. 



2 Professor W, S. FRANKLIN, The Second Law of Thermodynamics: its basis 

 in Intuition and Common Sense. Pop. Science Monthly, March, 1910. 



