WHAT IS ELECTRICITY ? jj 



what electricity is, any more than we shall know what energy is. 

 What we shall be able jDrobably to discover is, the relationship be- 

 tween electricity, magnetism, light, heat, gravitation, and the attract- 

 ing force which manifests itself in chemical changes. We have one 

 great guiding principle which, like the pillar of cloud by day, and the 

 pillar of fire by night, will conduct us, as Moses and the Israelites were 

 once conducted, to an eminence from which we can survey the prom- 

 ised scientific future. That principle is the conservation of energy. 

 To-day we see clearly that there are not different kinds of forces ; 

 that light is not one thing and heat another ; that, in truth, we should 

 blot the word light from our physical text-books ; that electricity and 

 magnetism have their equivalents in heat, and heat in mechanical 

 work. The ancients had a god for every great manifestation of Na- 

 ture — a god of peace, a god of war, a god of the land, a god of the 

 sea. Fifty years ago scientific men were like the ancients. There was 

 a force attached to every phenomenon of Nature. Thus, there were 

 the forces of electricity and magnetism, the vital forces, and the 

 chemical forces. Now we accept treatises on mechanics which have 

 the one word " Dynamik " for a title ; and we look for a treatise on 

 physics, which shall be entitled " Mechanical Philosophy," in which 

 all the phenomena of radiant energy, together with the phenomena of 

 energy, which we entitle electricity and magnetism, shall be discussed 

 from the point of view of mechanics. It is true that Mascart and 

 Joubert have entitled their treatise on electricity and magnetism " The 

 Mechanical Theory of Electricity and Magnetism " ; but what we are 

 to have in the future is a treatise which will show the mechanical re- 

 lations of gravitation, of so-called chemical attracting force and elec- 

 trical attracting force, and the manifestations of what we call radiant 

 energy. 



When we survey the field of modern physics, we see that there is 

 a marked tendency to simplify our conceptions. The question is 

 sometimes asked. How shall the man of the future be able to make 

 any advance, since it now takes one until middle age to gain famil- 

 iarity with the vortex theories, with quaternions, and the more or 

 less complicated mathematical analysis which characterizes our me- 

 chanical theory of electricity to-day ? It is evident that much of our 

 complicated scaffolding is to be taken down, and the student of elec- 

 tricity in the future will start with, perhaps, the laws of vortices as 

 axioms, just as the student in physics to-day starts with the truth that 

 the energy which we receive from the sun does not exist either as 

 light or heat in the space between us and the sun, but may be elec- 

 tro-magnetic, or even in an unsuspected form ; and that light and 

 heat are merely manifestations of waves of energy differing only in 

 length. 



We have reduced our knowledge of electricity and magnetism to 

 what may be called a mechanical system, so that, in a large number 



