ON THE STATISTICAL VIEW OF NATURE. 593 



undisputed and indisputable bases.^ In proportion a8 

 this has been done the calculated results have proved 

 to be in closer and closer accord with observed facts. 1 

 will here mention only one of the latest achievements 

 in this line of research and reasoning. Assuming — as 

 the atomic and kinetic theories do — that all external 

 phenomena of bodies can be reduced to the collective 

 or mean effect of a practically infinite variety of tur- 

 bulent movements of a very large number of particles, it 

 must be possible to give a mechanical explanation of 

 that remarkable property of all phenomena of nature, 29. 



■^ Irreversi- 



tirst noticed by Lord Kelvin, that they are essentially |^^'|*yj|'' 

 irreversible — i.e., that, with very rare exceptions, they i"'"<=e-''«es. 

 take place in a certain direction which we may define as 

 an equalisation of existing diflterences of level, tempera- 

 ture, electric pressure, and similar inequalities. In order 

 to fix this remarkable property of all natural phenomena, 

 physicists found themselves obliged to introduce, along- • 

 side of energy and mass (which are both assumed to 

 conserve or maintain their total quantity), a third some- 

 thing which is the measure of the degree in which an 

 existing distribution of mass and energy can be con- 

 sidered to be capable of external, visible, finite activity 



^ Those who are interested in 'Mathematical Appendix,' ]>. 17 ; 



seeing how difficult it is to link and the great number of memoirs 



together the common-sense argu- , referred to on p. 60 of that book, 



ments of the theory of probabilities , Nevertheless Tait speaks of the still 



in a consistent chain of unimpeach- 

 able logic, should read the report 

 on the various attempts to prove 



remaining difficulties in the kinetic 



theory of gases as having been 



' greatly enhanced by an apparently 



Clerk-Maxwell's law (mentioned in ; unwarranted application of the 



the foregoing note) contained in I theory of probabilities on whicli 



Prof. 0. E. Meyer's ' Kinetische I the stiitistical method is based." 



Thoorie der Gase' (2nd ed., Breslau, ('Properties of Matter,' •2nd ed., 



1899), esiiecially p. 46, ic, and 1 1890, p. 291.) 



VOL. II. 2 P 



