170 Br. J. A. Fleming [May 30, 



and if so in what way. In other words, can we have an unelectri6ed 

 corpuscle, or is the corpuscle so identified with its electric charge 

 that they are one and the same thing ? It has been shown experi- 

 mentally that an electric charge in motion is in effect an electric 

 current, and we know that an electric current possesses something 

 equivalent to inertia, that is, it cannot be started and stopped 

 instantly, and it possesses energy. We call this electric inertia 

 inductance, hence the question arises whether the energy of the 

 corpuscles when in motion is solely due to the electric inductance 

 or whether it is partly due to what may be called the ponderable 

 inertia of the corpuscle. 



This very difficult question has not yet been even approximately 

 settled. At the present moment we have no evidence that we can 

 separate the electron charge from the corpuscle itself. If this is 

 the case, then the corpuscles taken together constitute for all practical 

 purposes negative electricity, and we can no more have anything 

 which can be called electricity apart from corpuscles than we can 

 have momentum apart from moving matter. For this reason it is 

 sometimes usual to speak of the corpuscle carrying its charge of 

 one electron of negative electricity simply as an electron, and to drop 

 all distinction between the electric charge and the vehicle in or on 

 which it is conveyed. 



It is remarkable that so far no one has been able to produce or 

 find a corpuscle positively electrified. Positive electricity is only 

 known in association with masses as large as atoms, but negative 

 electricity is united with corpuscles or masses only a small fraction 

 of the size of an atom. This does not prove that an atom may not 

 include positive corpuscles or electrons, but only that so far we have 

 not been able to isolate them. 



The Electronic Theory of Electricity. 



From this point of view a theory of electricity originates called 

 the electronic theory. The principal objects of consideration in this 

 theory are these electrons which constitute what we call electricity. 

 An atom of matter in its neutral condition has been assumed to con- 

 sist of an outer shell or envelope of negative electrons associated with 

 some core or matrix which has an opposite electrical quality, such 

 that if an electron is withdrawn from the atom the latter is left posi- 

 tively electrified. 



A neutral atom minus an electron constitutes the natural unit of 

 positive electricity, and the electron and the ueutral atom minus an 

 electron are sometimes called negative and positive ions. Deferring 

 for a moment a further analysis of possible atomic structure we 

 may say that with the above hypothesis in hand we have then to 

 express our statements of electrical facts in terms of the electron as 

 the fundamental idea. 



All that can be attempted here is a very brief exposition of the 



