Septembee 21, 1900.] 



SCIENCE. 



435 



ogy of chemical actions, and assert that it 

 cannot in the long run increase the mechan- 

 ical availability of energy — that is, con- 

 sidering the organism as an apparatus for 

 transforming energy without being itself in 

 the long run changed. But we cannot es- 

 tablish a Carnot cycle for a portion of an 

 organism, nor can we do so for a limited 

 period of time ; there might be creation of 

 availability accompanied by changes in the 

 organism itself, but compensated by de- 

 struction and the inverse changes a long 

 time afterwards. This amounts to assert- 

 ing that where, as in a vital system or 

 even in a simple molecular combination, 

 we are unable to trace or even assert com- 

 plete dynamical sequence, exact thermody- 

 namic statements should be mainly confined 

 to the activity of the existing organism as 

 a whole ; it may transform inorganic ma- 

 terial without change of energy and with- 

 out gain of availability, although any such 

 statements would be inappropriate and un- 

 meaning as regards the details of the proc- 

 esses that take place inside the organism 

 itself. 



In any case it would appear that there is 

 small chance of reducing these questions 

 to direct dynamics ; we should rather re- 

 gard Carnot's principle, which includes the 

 law of uniformity of temperature and is 

 the basis of the whole theory, as a property 

 of statistical type confined to stable or per- 

 manent aggregations of matter. Thus no 

 dynamical proof from molecular considera- 

 tions could be regarded as valid unless it 

 explicitly restricted the argument to per- 

 manent systems; yet the conditions of 

 permanency are unknown except in the 

 simpler cases. The only mode of discus- 

 sion that is yet possible is the method 

 of dynamical statistics of molecules intro- 

 duced by Maxwell. Now statistics is a 

 method of arrangement rather than of de- 

 monstration. Every statistical argument 

 requires to be verified by comparison with 



the facts, because it is of the essence of 

 this method to take things as fortuitously 

 distributed except in so far as we know the 

 contrary ; and we simply may not know 

 essential facts to the contrary. For ex- 

 ample, if the interaction of the aether or 

 other cause produces no influence to the 

 contrary, the presumption would be that 

 the kinetic energy acquired by a molecule 

 is, on the average, equally distributed among 

 its various independent modes of motion, 

 whether vibrational or translational. As- 

 suming this type of distribution to be once 

 established in a gaseous system, the dy- 

 namics of Boltzmann and Maxwell show 

 that it must be permanent. But its as- 

 sumption in the first instance is a result 

 rather of the absence than of the presence 

 of knowledge of the circumstances, and 

 can be accepted only so far as it agrees with 

 the facts; our knowledge of the facts Qf 

 specific heat shows that it must be re- 

 stricted to modes of motion that are homol- 

 ogous. In the words of Maxwell, when 

 he first discovered in 1860, to his great 

 surprise, that in a system of colliding rigid 

 atoms the energy would always be equally 

 divided between translatory and rotatory 

 motion, it is only necessary to assume, in 

 order to evade this unwelcome conclusion, 

 that ' something essential to the complete 

 statement of the physical theory of mo- 

 lecular encounters must have hitherto es- 

 caped us.' 



Our survey thus tends to the result, that 

 as regards the simple and uniform phe- 

 nomena which involve activity of finite 

 regions of the universal sether, theoretical 

 physics can lay claim to constructive func- 

 tions, and can build up a definite scheme ; 

 but in the domain of matter the most that 

 it can do is to accept the existence of such 

 permanent molecular systems as present 

 themselves to our notice, and fit together 

 an outline plan of the more general and 

 universal features in their activity. Our 



