CLASSICAL AND NEW MECHANICS 153 



of this something we have called light. It is sur- 

 prising that men of science should believe that they 

 have proved the existence of the ether, as when Sir 

 Oliver Lodge states that it is the most massive thing 

 imaginable; or that space is occupied by energy, an 

 entity possessing inertia and probably gravitational 

 force, as Professor Einstein announces: they should 

 see that such statements are not deductions made from 

 our experimental knowledge of light, but are already 

 contained in the postulate that light is mechanical and 

 has a mechanical velocity. 



It is instructive to consider, in this connection, how 

 we also have attached hypothetically the science of 

 electricity to mechanics. The fundamental phenome- 

 non observed, when bodies are electrified or magnet- 

 ized, is that they attract or repel each other with a 

 mechanical force which, like the force of gravitation, 

 varies inversely as the square of the distance between 

 them. In our fundamental units this mechanical force 

 is equal to a mass times a length and divided by the 

 square of a time. Now Coulomb, who discovered 

 and measured the law of electrical attraction, believed 

 that electricity was a kind of fluid substance, such as 

 was always introduced when phenomena were obscure ; 

 and with this idea in his mind, he employed the term 

 quantity of electricity to indicate an analogy with a 

 quantity of matter. On this supposition, a quantity 

 of electricity expressed in mechanical units is equal to 



