﻿Atomic Model with a Magnetic (lore. 717 



of nebular and coronal spectra, the nucleus for each of these 

 elements is probably complex. It is only to the simple 

 nucleus that we need attribute the small size necessary to 

 account for the large mass. 



The properties of a terrestrial element connected with its 

 atomic number N can be explained just as in the case of the 

 Rutherford atom, if the resultant positive charge of the 

 complex nucleus amount to Ne. In particular Bohr's theory 

 of the hydrogen spectrum remains unaffected if we attribute 

 a complex character to the nucleus, provided the resultant 

 positive charge of the nucleus be 4- e. 



The interesting results obtained by Nicholson in his paper 

 on Electromagnetic Inertia and Atomic Weight* appear 

 to the writer to indicate a diameter for the nucleus of an 

 atom of radium or of thorium considerably greater than that 

 formerly assigned. Thus it is suggested in the paper that 

 the a. particles in a thorium atom have a mean distance apart 

 comparable with the radius of an electron, 10 -13 cm. Now 

 as the atom of thorium must contain the equivalent of about 

 58 ol particles, it would appear that the radius of the com- 

 plex nucleus of thorium must be considerably greater than 

 10" 13 cm. 



The view to which we are thus led is that the central 

 portion of an ordinary atom may contain a and j3 particles, 

 or hydrogen nuclei in orbital motion. This motion would 

 give rise to an external magnetic field. But as the velocities 

 in question must presumably be less than that of light, the 

 radius of the magnetic core must be greater than that of the 

 simple nucleus of Rutherford, and is perhaps of the order of 

 10" 10 cm. 



Magnetism. 



The views of magnetism that are widely accepted at the 

 present time are those developed by Langevin and by Weiss. 

 An electron in orbital motion may be regarded as equivalent 

 to an elementary magnet. According to the theory of 

 Weiss there is a certain elementary magnet, the magneton, 

 which is common to the atom of a large number of diflterenl 

 substances. It was pointed out in a discussion on this 

 theory at a meeting of the German Naturforscherversammlung 

 in 1911, that there may be a connexion between Planck's 

 "universal constant" h and the magnetic moment of the 

 magneton. Nicholson regards tins constant as an angular 

 momentum. McLaren f identifies the natural unit of 



* Nicholson, Phys. Soc. Loud. Fob. 26, L916, 

 t McLaren, 'Nature/ vol. xcii. p. 165 (1918). 



