188 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1924 



and negative electrons^ which seem to be the building stones of the 

 universe ; that these two entities are electrical charges of exactly the 

 same magnitude, but of opposite sign, 'and that the mass or inertia 

 associated with the former is 1,845 times that associated with the 

 latter, so that practically the whole mass of the atom is concentrated 

 in the positive electrons within its nucleus. 



We all agree that when 'any of the electrons in the outer regions 

 of the atom are stimulated to radiate, they do so by virtue of falling 

 from a level of higher potential energy to one of lower, i. e., from a 

 level more remote from the nucleus to one nearer to it. 



And we all agree that the frequency of the emitted radi'ations is 

 proportional to the energy loss in the process of changing from the 

 one level to the other. Indeed, one of the most stimulating advances 

 which physicists have made in the past five years consists in the com- 

 plete demonstration of this Planck-Einstein-Bohr law of radiation. 

 Very recent experiments go even so far as to indicate that this law 

 holds not only for the radiations emitted by the changes in energy 

 levels of the electrons outside the nucleus, but also for the radiations 

 which originate in the nucleus itself — the so-called g'amma rays which 

 accompany changes within the nuclei of radioactive atoms. 



These results upon which we all agree are proof enough of the 

 amazing advances which have taken place, mostly within the past 

 ten years, in our ability to peer inside the atom and to see what kind 

 of entities exist there and what they are doing when they are in the 

 act of radi'ating. 



The only place where we have differences of opinion, or better, in 

 which there are uncertainties, is in the matter of how the electrons 

 spend their leisure time — the portions of their lives in which they 

 are not radiating. 



The chemist has in general been content with what I will call the 

 " loafer " electron theory. He has imagined these electrons sitting 

 around on dry goods boxes at every corner ready to shake hands with, 

 or hold on to, similar electrons in other atoms. The physicist, on the 

 other hand, has preferred to think of them as leading more active 

 lives, playing ring-around-the-rosy, crack-the-whip, and other in- 

 teresting games. In other words, he has pictured them as rotating 

 with enormous speeds in orbits, and as occasionally flying out of 

 these orbits for one reason or another. 



' It is highly to be desired that this historically correct, etymologically most suitable, 

 and authoritatively reeo^iized nomenclature (see Rutherford's B. A. address 1923, 

 Nemsts Physical Chemistry, last edition, eta) be retained. When used without a prefix 

 or qualifying adjective the word electron may signify both the generic thing, the unit 

 electrical charge (this it does, in f.act, signify both historically and derivatively), and at 

 the same time the negative member of the species, in precisely the way in which the 

 word man is used without a prefix to designate both the genus homo and also the male 

 of the species. There is no gain in convenience by the use of the word proton and a 

 distinct loss logically, etymologically, and historically. 



