HYPOTHESIS OF RADIANT MATTER 69 



drawn the consequences in the most rigid fashion. I do assert, 

 however, that some of their fundamental terms are used in a 

 different sense from that to which we are accustomed, and 

 that we are, therefore, entitled to doubt whether the con- 

 clusions which they reach really affect the phenomena with 

 which the chemist deals: as if one were to discuss the crystal- 

 lographic structure of Pentelian marble with reference to the 

 architecture of the Parthenon. 



A few examples, pertinent to our inquiry, will more pre- 

 cisely establish my meaning. One of the fundamental postu- 

 lates of Professor Thomson's mathematical argument is the 

 definition of momentum as the product of mass by velocity. 

 Although this is not axiomatic, we accept it as such by reason 

 of the many ballistic experiments which have proved its truth, 

 so long as the projectile's mass was assumed to remain con- 

 stant: we should hesitate if we were told that mass was to 

 vary, i.e., that a bullet which weighs the same before and after 

 the shot, was heavier during its flight. But the momentum 

 of Thomson's electrons increases faster than their velocity, 

 when the latter approaches that of light; hence, he says, the 

 mass of the electrons increases with their swiftness. True, he 

 calls it an electro-magnetic mass, but some of his followers 

 have forgotten the distinction. At all events, his terms " mo- 

 mentum " and " mass " must not be accepted by us in their 

 usual meaning. 



It is perfectly true that Thomson's calculations are corrob- 

 orated by Kaufmann's experiments on the velocity of 

 radium rays in combined electric and magnetic fields, if the 

 latter 's data are calculated according to Thomson's views; 

 without even seeking a radically different basis which 

 would not be difficult we can follow Thomson to a point 

 where his departure from ordinary assumptions becomes evi- 

 dent. He shows that the value elm diminishes at high veloc- 



