6 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 65 



only one classical electron, or a very few such, for these would 

 radiate energy excessively fast. 1 



In a paper on " The Magnetic Properties of Systems of Cor- 

 puscles describing Circular Orbits " (Phil. Mag., 6, 673, 1903) he 

 shows, however, that when the number in an orbit is as great as six 

 and their linear velocity is small compared with that of light, the 

 loss of energy becomes quite, slow ; and therefore he attempts to 

 explain magnetic phenomena by means of rings of many corpuscles 

 (electrons). 



Now there are two great objections to such an explanation. In 

 the first place, subsequent work by Barkla and others has shown that 

 the lighter atoms, such as those of Hydrogen, Helium, Lithium, do 

 not contain enough electrons to form even one such ring. It may be 

 argued here that perhaps this evidence does not cover the total 

 electron content of the atom. But at least it indicates that a certain 

 number of electrons, distinct from the rest (if any), cannot be in 

 orbital motion : and it is important to notice that these are the more 

 loosely bound electrons, which play a part in chemical, magnetic, and 

 optical phenomena. 



The second objection originates in the fact that for diamagnetic 

 atoms it is necessary to assume the existence of independent orbits 

 in the atom that are so great in number or else undergo such rapid 

 variations that they can be considered to have their axes uniformly 

 distributed in three dimensions — this to account for a zero resultant 

 magnetic moment. Now separate rings of this sort cannot maintain 

 their individualities unless the difference in their radii is so great 

 that their disturbance of one another is inappreciable. This con- 

 dition, if granted, would limit the possible number of rings and the 



1 Thomson has more recently proposed an electron with such properties that 

 it could rotate in an orbit by itself. This is the electron with all its field con- 

 centrated along a narrow cone, or, to adopt Faraday's mechanism, with a 

 single tube of force. Although he has not attempted to develop a theory of the 

 structure of the atom from this, or to explain radiation or magnetism by it, 

 he has used the conception in a theory of chemical affinity (Phil. Mag., May, 

 1914), though in a manner that is not at all definite, as may easily be imagined 

 from the following considerations. Since the electron is attached to its 

 equivalent positive charge by means of its single tube of force, it cannot exert 

 any electric force upon any other body, and, even if it is in stable orbital 

 motion, it cannot for the same reason give rise to magnetic forces or any sort 

 of radiation. Hence, unless we accept some entirely new and at present incon- 

 ceivable view of the properties of the electromagnetic field, such an electron 

 is a wholly unprofitable conception. The assumptions made in Bohr's theory 

 involve similar difficulties, which, however, are ignored in its development. 



