352 Proceedings of the Poyal Society of Edinburgh. [Sess. 
XXIV. — Chemical Combination and Sir Alfred Ewing’s Magnetic 
Atom. By Principal A. P. Laurie, M.A., D.Sc. 
(MS. received July 14, 1922. Eead June 19, 1922.) 
The outcome of recent investigations into the properties of matter has 
been to show that the atom, in all probability, consists of a positive 
nucleus surrounded by electrons. The distribution of the electrons round 
the positive nucleus is controlled b}^ the attraction of the positive nucleus 
on the electrons and by the repulsion of the electrons for each other. Sir 
J. J. Thomson and others have investigated mathematically and experi- 
mentally the laws governing such a distribution, on the assumption that 
the electrons are stationary in relation to each other and to the positive 
nucleus. 
It is also probable from the experimental evidence that atoms of 
elements containing a considerable number of electrons consist of an inner 
stable group of electrons round the positive nucleus with an outer shell 
containing the electrons which take part in chemical change. We also 
have evidence that when elements combine to form salts which are capable 
of ionisation one or more electrons pass from one atom to the other. It 
is evident that the simplest possible conception of the atom is that of a 
positive element surrounded by stationary electrons, and many chemical 
phenomena have been explained in terms of this simple atom by Sir J. J. 
Thomson and others. 
It is, however, by no means certain that the electrons are stationary. 
They are quite possibly moving in orbits with the nucleus as a centre, 
or they may be moving in tiny orbits of their own, each orbit occupying 
a fixed position with reference to the other orbits, and the positive 
nucleus thus endowing the electron with magnetic as well as electrostatic 
properties. 
We may also, instead of assuming the electron to be moving in an 
orbit small compared with the size of the atom, adopt the assumption 
made by A. L. Parson that the electron is a continuous negative charge 
disposed round a ring, and that this ring is rotating with a velocity 
approaching the velocity of light and so producing a magnetic shell. 
To this conception of the electron Parson has given the name of the 
magneton. We shall assume in the subsequent discussion that the atom 
consists of a positive nucleus surrounded by electrons holding fixed posi- 
tions in space in relation to the surrounding electron and to the nucleus. 
