pose 
XUITI. 
AWARD OF THE BOYLE MEDAL TO PROFESSOR re: 
LEE DTSMLO INS Mlgalon, IDGISie, italg tse, IMS 
In recommending that the Boyle Medal be this year awarded to- 
_ Professor Thomas Preston, the Science Committee have more 
especially in view the recent important advances which Professor 
Preston has effected in our knowledge of the phenomena attending 
radiation in a magnetic field, which work he has communicated to: 
this Society during the last two years. 
Your Committee in the first place desire to place on record 
their great regret at the unfortunate illness which alone has. 
hindered Professor Preston from continuing the investigation. 
Meanwhile they submit that sufficient has been accomplished by 
Professor Preston to mark important advance in this field of 
research. 
Early in 1897 the broadening of the spectral lines arising from 
radiation in a strong magnetic field was announced by Dr. P. 
Zeeman ; and about the middle of that year, Dr. Zeeman further 
announced the fact that the triple nature of some of these lines. 
had been established by aid of the differing polarisation of the 
central and lateral bands. ‘This important.experimental work was. 
the first completely successful accomplishment of an experiment 
undertaken by Faraday, so long ago as 1862. The theoretical 
aspect of Zeeman’s first experiments had been examined by 
Professor Lorentz and by Dr. Larmor. ‘The threefold nature of 
the broadened lines as well as their polarisation phenomena had 
been predicted by these mathematicians, and also the probability 
that the change of wave-length introduced by the magnetic force 
should be proportional to the square of the wave-length of the 
affected hoes 
1 The presentation took place at the Council Meeting of February the 8th, 1900, 
when the medal was handed by the Chairman (Right Hon. Viscount Powerscourt, K.P.) 
to Professor G. F. FitzGerald, F.T.C.D., F.R.S., on behalf of Professor Preston, who, 
owing to illness, was unable to be present. 
SCIENT. PROC. R.D.S., VOL. IX., PART IV. 258 
