240 Proceedings of the Royal Society of Edinburgh. [Sess. 
Advances in Electricity and Magnetism, he tackled in his own way the 
many difficult questions suggested by that treatise, and applied his mind 
to the mastery of vector algebras as an aid in electro-magnetic investigation. 
From the notes he sent home at intervals it was abundantly evident that, 
with scanty help from the ordinary sources, he was himself constructing 
his own vector methods, largely retreading paths which, unknown to 
him, had been trodden by his predecessors, Hamilton, Tait, Heaviside, 
M‘Aulay, Gibbs, and others. So impressed were his scientific friends with 
the brilliancy shown by Gordon Brown that an effort was made to get 
him appointed to a less dangerous post ; but he himself would not listen 
to the proposal. 
His correspondence is particularly interesting as throwing light on the 
way his mind was working. For example, in a letter written to his 
mother from Haslar R.N. Hospital of date December 5, 1915, we find 
the following : — 
“ Up to the present I have written a first scroll of (1) the first part of 
a paper on ‘ The Faraday -tube Theory of Electro-magnetism,’ of which you 
will find an elementary discussion in Thomson’s Electricity and Matter I 
have in the house as a prize. I think this first part, which deals with the 
theory in general, and shows that on simple assumptions it leads in general 
(as it ought) to what are called the Five Equations of Electro-magnetism, 
of which the first four are the epitome of Maxwell’s theory, and the Fifth 
Equation is due to Lorentz or possibly (in justice) to Heaviside — I think 
this part of the paper may be of interest in itself, and is almost certain to 
be correct and original. The second part I am only just commencing. . . . 
Its purpose would be to apply the Faraday-tube theory to special 
problems, such as the law of gravitation, the structure of the atom, and 
the density of energy in radiation in temperature equilibrium with matter. 
. . . Besides working the first part of the paper, I have written a rough 
note on the ' Energetics of the Electron,’ which is fairly short, and more 
on the lines of the work I had published in August.” (See Phil. Mag., 
August 1915, “ Note on Reflections from a Moving Mirror.”) 
The paper referred to above is the one now being published ; and a 
more particular account of its genesis was given to Dr Pinkerton, in a 
letter written about the middle of January 1916. This letter brings out 
the writer’s keen critical faculty, and his determination not to accept any- 
thing which was not fully understood by him : — 
‘'Dear Dr Pinkerton, — I am ashamed to trouble you again about my 
scribbling, but as I am now having typed a paper which you yourself — 
