212 SCIENCE AND METHOD. 



have no further meaning, or else it must designate the 

 fictitious electro-magnetic mass ; in that case mass will 

 no longer be constant, transversal mass will no longer 

 be equal to longitudinal mass, and the principles of 

 Mechanics will be upset. 



And first a word by way of explanation. I said 

 that, for the same charge, the total mass of a positive 

 electron is much greater than that of a negative electron. 

 Then it is natural to suppose that this difference is 

 explained by the fact that the positive electron has, 

 in addition to its fictitious mass, a considerable actual 

 mass, which would bring us back to the first hypothesis. 

 But we may equally well admit that the actual mass 

 is nil for the one as for the other, but that the fictitious 

 mass of the positive electron is much greater, because 

 this electron is much smaller. I say advisedly, much 

 smaller. And indeed, in this hypothesis, inertia is of 

 exclusively electro-magnetic origin, and is reduced to 

 the inertia of the ether ; the electrons are no longer 

 anything in themselves, they are only holes in the 

 ether, around which the ether is agitated ; the smaller 

 these holes are, the more ether there will be, and the 

 greater, consequently, will be its inertia. 



How are we to decide between these two hypotheses ? 

 By working upon the canal-rays, as Kaufmann has 

 done upon the ^ rays? This is impossible, for the 

 velocity of these rays is much too low. So each must 

 decide according to his temperament, the conservatives 

 taking one side and the lovers of novelty the other. 

 But perhaps, to gain a complete understanding of 

 the innovators' arguments, we must turn to other 

 considerations. 



