THE PHILOSOPHY OF SCIENCE 415 



actually an accretion of mass with velocity. There are a 

 number of interpretations possible. It may be that that of 

 Sir Oliver Lodge is the correct one. But certainly that of the 

 exponent of non-Newtonian mechanics is wrong. On this 

 point, no words can be clearer than those of Sir Oliver Lodge ! : 



" That mass is constant is only an approximation. That 

 mass equal to ratio of force and acceleration is a definition and 

 can be absolutely accurate. It holds perfectly even for an 

 electron with a speed near that of light. ... I urge that we 

 remain with or go back to Newton. I see no reason against 

 retaining all Newton's laws, discarding nothing, but supple- 

 menting them in the light of further knowledge." 



On the question of metageometry, the address is not so 

 clear, but, here again, we can apply still further the underlying 

 principles. In Riemann's space, a line returns on itself. In 

 the space of Lobatschewsky, " parallel" lines bend apart. Does 

 either of these or Euclidean space represent actual space ? To 

 this question there is only one possible answer. The line 

 returning on itself is not straight, and the bending parallel 

 straight lines are neither straight nor parallel. No possible 

 experiments can alter or modify this fundamental. It may 

 be that non-Euclidean geometry is applicable to real existent 

 conditions. It may be that the parallaxes of very distant stars 

 are negative, and there may be means of proving that the 



1 There is, however, one point on which Sir Oliver Lodge is not quite 

 clear. He speaks of variable masses, and compares electrons to raindrops or a 

 locomotive. Elsewhere, he says : " The dependence of inertia and shape on 

 speed is a genuine discovery and, I believe, a physical fact." The writer is pre- 

 pared to admit this only on the same assumption that is applied to raindrops — 

 that the additional mass comes from somewhere. It is not clear whether or no 

 this is Sir Oliver Lodge's meaning. If not, I would add it as a corollary. I 

 regard the indestructibility of mass as as fundamental an axiom as the unchange- 

 ability of space and time, and I am not aware of any more fundamental measure 

 of mass than inertia. 



The idea has occurred to me that electrons, when their velocity exceeds a 

 certain amount, may meet with some resistance from the cether, and that the very 

 experiments which have occasioned a doubt as to its existence may be an 

 additional means of proving it. As I have not had an opportunity of witnessing 

 the actual experiments, I merely put this forward as a suggestion and with all 

 reserve. I am informed that there is some objection on the ground of the path 

 of the /3 rays, but that the experiments have not been performed with sufficient 

 care to enable us to speak definitely, hence the reserve. But, personally, on 

 present knowledge, I am inclined to think variable resistance more probable than 

 variable mass- 



