Structure of the Atom. 259 



electrons do not revolve around a nucleus ; in the latter, 

 as in Dr. Bohr's scheme, they may so revolve. In the latter, 

 bright line emission may arise from the revolution of electrons 

 in the steady state ; in Dr. Bohr's scheme there is no emis- 

 sion, or practically none, in steady states, bright lines being 

 due to vibrations induced— in a manner not specified because 

 it is not within the scope of ordinary dynamics — -by the 

 passage of the system from one steady state to another. 



Though all such possibilities ought to be considered, for 

 they are directly suggested by actual phenomena, it does 

 not seem to me that we are yet under compulsion to forsake 

 the laws of ordinary dynamics in connexion with atomic 

 properties, or the doctrine of a continuous wave-front in 

 aether, or even, apart from magnetic action, the notion of 

 central symmetry in atomic action. 



§ 2. A centrally symmetrical Atom. 



To meet the condition of stable circulation of electrons we 

 must have regions of attractive force, To meet the conditions 

 of expulsion of electrons, without necessary absorption of 

 much radiational energy, we must have regions of repulsive 

 force alternating with the former ; and the total work done 

 by the forces of repulsion on an ejected electron must 

 exceed that done on it by the attractive forces by the amount 

 necessary in order to account for the speed of ejection. The 

 law of radial variation of force must be such as to account 

 for any observed spectrum series, 



Subject to these conditions many different structural 

 arrangements may be postulated. We are not necessarily 

 bound down to the law of repulsion according to the inverse 

 cube of the distance, or to constancy of angular momentum 

 of the electrons. On other bases, different interpretations of 

 the dynamical significance of Planck's constant h from that 

 given by Nicholson would be furnished. But it is of interest 

 to discuss the spherical counterpart of the tubular atom of 

 Bir J. J. Thomson (Phil Mag. Oct. 1913), 



Let there be relatively broad regions in which the law of 

 radial acceleration is 



.. Ae 



e and m being the charge and mass of an electron. The 

 volume density of a distribution of electricity giving rise to 

 this is /?= +3A/47rr 4 outside an interior radius a. which 

 includes within it an amount of negative electricity equal to 

 A/#, If now, over the spherical surface of radius r»' > », 



132 



