226 ANNUAL REPORT SMITHSONIAN INSTITUTION, 19 3 5 



may be called the sphere of the electron. This sphere contains an 

 equal number of positive and negative charges, forming a little Ken- 

 nelly-Heaviside layer around the nucleus. Measurements on the 

 diffraction rings indicate a diameter for this sphere at least 10,000 

 times that previously accepted as the diameter of the electron. 



III. The nucleus is the center of a gi"oup of waves and moves with 

 the group speed in its atmosphere of electric charges. 



At the time that J. J. Thomson proposed this hypothesis the posi- 

 tive electron was not known. Here comes in the importance of Rupp's 

 work previously referred to. On their face these experiments indi- 

 cate either that the train of waves that accompanies a negative elec- 

 tron is absent from the positive electron, or that all possible wave 

 lengths are present. 



Just as the atom, once regarded as an ultimate structural unit, is 

 now recognized as a complex of electrons, protons, neutrons and pos- 

 sibly neutrinos, so the electron, it seem^, must be regarded as a 

 similar complex. Much more, doubtless, is to be learned about its 

 structure before we can hope to answer the question, Wliat is 

 electricity ? 



Perhaps the most outstanding fact in modern physical theory is 

 the dominant position occupied by electricity. In the nineteenth 

 century one spoke of matter and electricity as two separate and in- 

 dependent entities; nowadays electricity has become the funda- 

 mental entity of which matter is merely an aspect. Matter, once 

 supreme, has lost its individuality and has become merely an elec- 

 trical phenomenon which electricity may exhibit more or less accord- 

 ing to circumstances. 



It is obvious that our answer to the question: What is electricity? 

 will be fundamentally influenced according to whether we hold an 

 electrical theory of matter or a material theory of electricity. It will 

 therefore be worth our while to examine the foundation for the 

 present view that electricity, whatever it may be, is the sole world- 

 stuff. So radical has been this change in our thinking that it would 

 seem a foregone conclusion that it must be based upon the clearest 

 and most unequivocal of experimental evidence. 



This change in our concepts did not come suddenly. Its beginning 

 dates back to 1893, when J. J. Thomson ^^ showed on theoretical 

 grounds that a charged sphere in motion through the ether would en- 

 counter a resistance which to all intents and purposes would appear 

 as an increase in the sphere's inertia, i. e., in its mass. Calculation 

 indicated that this effect would become appreciable only if the 

 velocity of the charged body was comparable to that of light. 



''* Thomson, J. .7., Recent Researches In Electricity and Magnetism, p. 21. Clarendon 

 Press, Oxford, 1893. 



