Award of the Boyle Medal and Rep. of Sci. Com. R.D.S. 545 
hardly been hitherto adduced. This law he illustrates by the case 
of three substances:—magnesium, cadmium, and zine. The law 
expresses the fact that not only are similar lines in the series of 
chemically related elements similarly modified by the magnetic 
field, but that the value 
dn 
» 
is, in these cases, the same. The importance of this law, whether 
the theory of ions is accepted or not, is accentuated in M. Cotton’s 
able review of the present state of the investigation. (Le 
Phénoméne de Zeeman, Scientia, Oct. 1899.) 
In the course of these researches Prof. Preston was gradually 
increasing the strength of his magnetic field, and lately was using 
a magnet built to his own design attaining a field of 40,000 cgs. 
units. The design of this magnet is original, but a published 
account of it has not yet appeared. 
With the aid of this powerful instrument he was able to 
announce, in the addendum to his paper in the Trans. R. D.S. 
last referred to, that the quartet form hitherto noticed is really a 
sextet, the outer lines being feebly bipartite, that the normal 
triplets are not further resolved, and that the diffuse triplets are, 
in fact, nonets, consisting of unequally luminous lines. 
Contemporaneously with these papers, others, mainly recapitu- 
latory, appeared :— 
Phil. Mag. xly., 1898, p. 325. 
Pe exlviiee 1899 pa 165: 
Nature, vol. 59, Jan. 5, p. 224; March 23, p. 485; April 6, p. 683, 1899. 
A clear and lucid account of the whole matter is also to be 
found in the report of Prof. Preston’s lecture before the Royal 
Institution appearing in Nature, vol. 60, June 22, 1899, p. 175. 
It is satisfactory to find how clearly in his later papers, Prof. 
Preston recognises the pioneer work of Dr. G. J. Stoney (upon 
whom this Society conferred the Boyle Medal last year). 
On Dr. Stoney’s conception oi the ionic charge, originating by 
its orbital and orbital-apsidal motions, sequences of dual lines in the 
spectrum, much has since been founded. Dr. Larmor uses a similar 
conception to explain, as before referred to, the triplet produced by 
the influence of the magnetic field. Herein is indicated the present 
great interest of the research into magnetic radiation. It appears 
