200 Prof. L. T. More on (lie 



and electrical energy, originating in one body, pass through 

 space undiminished and unaugmented to another body. We 

 can also express tbis energy as kinetic energy while it is 

 associated with matter. In transit, since our experience 

 gives us no clue or criterion, we can assume as a formula for 

 tbe energy, either a periodic motion of an hypothetical some- 

 tiring, called an aether, or a projectile motion of an hypo- 

 thetical mass-particle. In either case, all we really do is to 

 divide the initial or final material energy into two mathe- 

 matical quantities, one a mass-factor and the other a velocity- 

 factor, and give to each such a value as to make their product 

 remain a constant. As a rule, we make the mass-factor so 

 small that we can shut our eyes to its existen e and imagine 

 anything about it we please. The time relation is fixed by 

 experiment. For tbe purposes of theory, although this 

 radiant energy appeals to our senses in the three forms of 

 heat, light, and electricity, which in their qualitative respect 

 are each fundamental and not referable one to another, we 

 fortunately find that quantitatively all three are satisfied by 

 one dynamic formula. We have therefore obtained an 

 adequate quantitative knowledge of energy, but not an 

 inkling of tbe qualitative coefficients in this formula. 



The hypothesis of the aether is an attempt to accomplish 

 the impossible. And while it is now generally admitted 

 that we cannot create such a substance as will satisfy the 

 phvsical requirements of a transmitter of radiant energy, 

 still the aether is claimed to be a useful hypothesis. This 

 utilitv is said to consist in giving us a crude image, in a 



1/ OCT CT ? 



mechanical way, of what occurs. In other words, it lessens 

 our innate dislike to confessing complete ignorance, and it 

 provides a set of concrete analogies for abstract statements 

 and equations. Thus Poincare says in the preface to his 

 Thearie de la Lumiere: " Peu nous importe que Tether 

 existe reellement ; c'est Taffaire des metaphysiciens ; Tessen- 

 tiel pour nous c'est que tout se passe comme s'il existait et 

 que cette hypothese est commode pour 1'explication des 

 phenomenes. Apres tout, avons nous d'autre raison de croire 

 a l'existence des objets materiels ? Ce n'est la aussi qu'une 

 hypothese commode ; seulement elle ne cessera jamais de 

 Fetre, tandis qu'un jour viendra sans doute ou Tether sera 

 rejete comme inutile/' Now the old elastic-solid and 

 mechanical aether did afford us a concrete image and we 

 could speak of it with some intelligence to one another, 

 because everyone has a conception of an elastic solid. To 

 be sure, this solid aether became a grotesque. It permitted 

 the transference of heat and light energy, but only at the 



