AND OF THE SECOND LAW 41 



Here S is BOLTZMANN'S value H, wru"ch always changes 

 in one direction only; k is the universal integration constant 

 which is the same for a terrestrial as for a cosmical system, and 

 when it is known for one, it is known for the other; when k is 

 known for radiant phenomena it is also known and is the same 

 for molecular motions. 



There are some general statements which indicate more or 

 less rigorously some of the properties or features of the entropy 

 of a state. 



(a) Entropy is a universal measure of the " disorder " in the 



mass points of a system. 



(b) Entropy is a universal measure of the irreversibility of a 



state and is its criterion as well. 



(c) Entropy is a universal measure of nature's preference for 



the state. 



(d) Entropy is a universal measure of the spontaneity with 



which a state acts when it is free to change. 



(e) Entropy of a system can only grow. 



(f) Entropy asserts the essential one-sidedness of Nature. 



(g) There exists in Nature a magnitude which always changes 



in the same sense. 



(e), (f), and (g) imply change and therefore, strictly speaking, 

 should not be mentioned here but postponed to a later section. 



SECTION E 



EQUIVALENTS or CHANGE OF ENTROPY IN MORE OR LESS 

 GENERAL PHYSICAL TERMS 



Here we are really considering the Second Law, for change 

 of entropy is the kernel of this law, in fact is identical with it. 

 It will be profitable, however, to view this law in all its many 

 physical aspects. To be sure, in times past it has been accounted 

 a reproach to the Second Law that it should be stated in so many 



