39 
1920-21.] iEther and the Quantum Theory. 
then the physical nature of the lines must be granted also. The question 
of the existence of physical lines of force he regards as “ both important, 
and likely to be answered ultimately in the affirmative” (p. 437). Again, 
in the celebrated letter published under the title “ Thoughts on ray- 
vibrations” (p. 447) he writes: “The view which I am so bold as to put 
forth considers, therefore, radiation as a high species of vibration in the 
lines of force which are known to connect particles and also masses of 
matter together. It endeavours to dismiss the aether, but not the 
vibration.” “ It may be asked, what lines of force are there in nature 
which are fitted to convey such an action and supply for the vibrating 
theory the place of the aether ? ” “ The lines of weight or gravitating 
force are, certainly, extensive enough to answer in this respect any 
demand made upon them by radiant phaenomena ; and so, probably, are the 
lines of magnetic force. . . .” 
As is well known, Clerk Maxwell developed and gave mathematical 
expression to the views of Faraday, and one of his earliest papers deals 
with the illustration of Faraday’s lines of force by the lines of flow of a 
liquid (1856). As early as 1857 Faraday was speculating whether the 
velocity of propagation of magnetic action is of the same order as that of 
light, but Maxwell’s memoir, entitled “ A Dynamical Theory of the Electro- 
magnetic Field,” in which the electromagnetic theory of light was 
formulated, was not completed till 1864. 
Sir Joseph Thomson has developed extensively the theory of moving 
tubes of force, but unlike Faraday he regarded magnetism as a secondary 
effect, ascribing magnetic fields, not to the presence of magnetic tubes, but 
to the motion of electric tubes. The conception of lines of electric force 
stretching from positive to negative charges presents certain difficulties, 
as in the case where magnetic fields occur without any manifestation of 
electric force. In order to account for such facts it may be supposed that 
two sets of Faraday tubes exist starting from positive and negative 
charges respectively. In a steady magnetic field the positive and negative 
tubes may be thought of as moving in opposite directions with equal 
velocities. Such difficulties have led many physicists to reject the idea of 
the discrete existence of electrostatic tubes, in spite of the fact that “ they 
give a natural and simple explanation of the electrokinetic momentum in 
the aether ” (Jeans). 
The results of the present paper suggest that the magnetic tubes may 
be more fundamental than the electrostatic. 
§ 8. Faraday’s proposal to “ dismiss the aether ” seems to have reference 
to the particular view of the aether then prevalent. His own hypotheses 
