212 Prof. L. T. More on the 



In simplicity of formula the last two have the advantage, 

 and from general theoretical principles there is little to 

 choose between them. Here, too, the shape and other 

 definite properties of a fundamental element of matter 

 are not subject to proof and become finally a mere question 

 of definition. 



If the electron is rigid, we must expect to obtain mea- 

 surable and positive results in experiments, such as those of 

 Michelson and Morley, made on the mutual relations of the 

 quiescent sether and matter. These are now conceded to be 

 impossible, either from the principle of relativity or from 

 what, I think, is a more fundamental idea : that however 

 finely matter be divided, it maintains all such attributes as 

 potential energy. So if the electron is held to be rigid and 

 without potential energy, that attribute must be given to it 

 from some mutual relation between it and a plenum of which 

 it is a modification, such as is expressed by Poynting's 

 energy theorem. 



On the other hand, if the electron is deformable, work 

 must be done to produce this deformation. This can come 

 either from internal potential energy due to force actions of 

 its own parts, or from an unlimited reservoir, the aether. In 

 the first case, we are compelled to subdivide the electron, 

 which thus ceases to be a fundamental element of matter ; 

 and the second case leads us nowhere. 



Nor can the principle of relativity aid us in obtaining 

 positive knowledge on such questions ; at best it is a principle 

 of negation, stating in mathematical terms the idea long- 

 established in philosophy that all our knowledge is relative, 

 and must be so, from the fact of the finitude of our minds. 



If now we turn to the experimental evidence to decide 

 between these two forms of the electron, we come to no 

 definite decision. 



Kaufmann * concludes with the following remarks : — 

 " Die vorstehenden Ergebnisse sprechen entschieden gegen 

 die Richtigkeit der Lorentzschen und somit auch der Em- 

 steinschen Tbeorie i betrachtet man diese aber als widerlegt, 

 so ware damit auch der Versuch^ die ganze Physik ein- 

 schliesslieh der Elektrodjmamik und der Optik auf das 

 Prinzip der Relativbewegung zu grunden, einstweilen als 

 missgliickt zu bezeichnen. Eine Betrachtung der Einstein- 

 schen Theorie zeigt, dass man, um bei Beibebaltung dieses 

 Priuzipes dennoch Uebereinstimmung mit meinen Resultaten 

 zu erhalten, bereits die Maxwellschen Gleichungen fiir 



* Annul der Physik, xix. p. 534 (1906). 



