202 SCIENCE PROGRESS 



not necessarily rush together and annihilate each other, but 

 would form a doublet whose length would be comparable 

 with that of a single electron. Oscillatory motion would be 

 possible, and a radiation of wave-length comparable with the 

 " radius " of the electron would be emitted. 



This view that two ethereal structures can exist in this 

 way without deformation in the presence of each other, and 

 simultaneously occupy the whole ether, offers some difficulty, 

 no doubt ; but one no greater than that involved in the postu- 

 late that an electron composed of mutually repelling parts has 

 a definite boundary. It has the advantage of suggesting an 

 avenue of research in which one might resolve the difficulty 

 of the minute but complex nucleus. For instance, a neutral 

 doublet could be conceived as a distribution of electric density 

 given by an expression such as 



The total charge is zero when integration is extended through 

 all space. Considering Xi as less than X 2 , the density and 

 electric force are confined to a region round the origin of r 

 whose radius is of the order Ai" 1 almost precisely. The system 

 behaves like a pair of charges ±eat the origin of radii Xr 1 , Xa" 1 , 

 which can be separated by the application in a suitable form 

 of an amount of energy of the order \ x e 2 . Such a type of 

 doublet might form a component of a complex atomic nucleus ; 

 one would then preserve the extreme minuteness of the nucleus, 

 and also the property of radioactivity or partial dissolution 

 of the nucleus into positive and negative charges. 



Prof. Nicholson's second paper is printed in Part II. 

 (February 191 8) of the Proceedings. In it he criticises some of 

 the model atoms which have been employed by physicists to 

 elucidate points in the behaviour of atoms and molecules. 

 Nicholson himself in the Phil. Mag. (April and July 191 4) has 

 already pointed out that the Rutherford model is unstable 

 (according to the principles of Newtonian dynamics) unless all 

 the electrons are in one plane, rotating as a ring. True, this 

 difficulty is somewhat evaded by the non-Newtonian mechanics 

 worked out by Bohr (Phil. Mag. 1914, July, September, 

 December). But a pyramidal form of atom has been em- 

 ployed by Stark in building up theoretical molecules, and in 

 this paper Nicholson demonstrates the impossibility of their 



