128 THE LIMITATIONS OF SCIENCE 



eluding that a complete theory is not necessary. But 

 the history of science shows that we shall soon create 

 two media or try to give properties to one which will 

 include electrical, chemical, and material forces; in- 

 deed, this latter is already being attempted. If the 

 conception of an elastic solid ether was admittedly a 

 fiction of the mind, and one impossible to align with 

 any known kind of matter, the electro-magnetic ether is 

 so esoteric, so subtilized from all substance, that it 

 merely provides a nomenclature for a set of equations 

 expressing the propagation of radiant energy. We 

 may well go still further, for I believe the time is 

 rapidly approaching when all scientific discussion of 

 the nature of the ether will be considered futile. 



In accordance with my view no hypothesis will be 

 made to express properties of a medium, whose exist- 

 ence is itself incapable of scientific proof. It is, at 

 the same time, perfectly proper to distinguish space 

 through which we say radiant energy passes by a 

 special name such as the ether. The amount of 

 radiant energy in transit is best given by an equa- 

 tion expressing conservation of energy and con- 

 taining a velocity and an inertia factor. The 

 velocity factor of this equation most conveniently 

 takes the form of a periodic motion, but no assump- 

 tions need to be made as to the nature of the periodicity 

 or of the inertia factor, since they also are not subject 

 to experimental verification. 



