vi CONTENTS 



PAOB 



(3) Settled and unsettled states; distinction between final stage of " elemen- 



tary chaos " and its preceding stages .............. 18 



Each stage has sufficient haphazard; examples and characteristics of the 

 settled and unsettled stages of "elementary chaos"; all micro - 

 states not equally likely; the assumed state of " chaos " does not 

 eliminate adequate haphazard; two anticipatory remarks .......... 19 



SECTION B 



CONCERNING THE APPLICATION OF THE CALCULUS OF PROBABILITIES 



(i) The probability concept, its usefulness in the past, its present 



necessity, and its universality .................. 22 



Popular objection to its use; BOLTZMANN'S justification of this concept; 

 its usefulness in the past and in other fields; some of its good points; 

 the haphazard features necessary for its use .................... 23 



(2) What is meant by probability of a state ? Example ..... 27 



SECTION C 



(i) The existence, definition, measure, properties, relations and scope 



of irreversib ility and reversibility ................. 29 



Inference from experience; inference from the H-theorem or calculus of 

 probabilities; definitions of irreversible and reversible processes; 

 examples of each ............................................ 30 



(2) Character of process decided by limiting states ........ 32 



Nature's preference for a state; measure of this preference ............ 33 



Entropy both the criterion and the measure of irreversibility ......... 33 



(3) All the irreversible processes stand or fall together ...... 34 



(4) Convenience of the fiction, the reversible processes ...... 35 



Entropy the only universal measure of irreversibility. Outcome of the 



whole study of irreversibility ...... . ........................... 36 



