THE ELECTRIC AND LUMINIFEROUS MEDIUM. 
209 
On Material Models and Illustrations of the Mther and its associated 
Electrons, 
o. Although the Gaussian aspect of the subject, which would simply assert that 
the primary atoms of matter exert actions on each other which are transmitted in time 
across space in accordance with Maxwell’s equations, is a formally sufficient basis 
on which to construct physical theory, yet the question whether we can form a valid 
conception of a medium which is the seat of this transmission is of fundamental 
philosophical interest, quite independently of the fact that in default of the analogy 
at any rate of such a medium this theory would be too difficult for development. 
With a view to further assisting a judgment on this question, it is here proposed to 
desciibe a process by which a dynamical model of this medium can be theoretically 
built up out of ordinary matter,—not indeed a permanent model, but one which can 
be made to continue to represent the mther for any assignable finite time, though 
it must ultimately decay. The aether is a perfect fluid endowed with rotatioiial 
elasticity; so in the first place we have—and this is the most difficult part of our 
under taking to constiuct a material model of a perfect fluid, which is a type of 
medium nowhere existing in the material world. Its characteristics are continuity 
of motion and absence of viscosity : on the other hand in an ordinary fluid, 
continuity of motion is secured by diffusion of momentum by the moving molecules, 
which is itself viscosity, so that it is only in motions such as vibrations and slight 
undulations where the other finite effects of viscosity are negligible, that we can 
treat an ordinary fluid as a perfect one. If we imagine an aggregation of frictionless 
solid spheres, each studded over symmetrically with a small number of frictionless 
spikes (say four) of length considerably less than the radius, “so that there are a very 
large number of spheres in the differential element of volume, we shall have a 
possible though very crude means of re|)resentation of 
an ideal perfect fluid. There is next to be imparted to 
each of these spheres the elastic property of resisting 
absolute rotation ; and in this we follow the lines of 
Lord Kelvin’s gyrostatic vibratory sether. Consider 
a gyrostat consisting of a flywheel spinning with angular 
momentum g, Avith its axis AB pivoted as a diameter on 
a ring whose perpendicular diameter CD is itself phmted 
on the sphere, which may for example be a hollow shell 
with the flywheel pivoted in its interior; and examine 
the effect of imparting a small rotational displacement to the sphere. The direction 
of the axis of the gyrostat will be displaced only by that component of the rotation 
^ The use of these studs is to maiutaiii coutiuuity of motiou of the medium without the aid of 
. ' ^ ’ ^ud also (§ 4) to compel each sphere to participate iu the rotation of the element of volume 
ot 1 10 medium, so that the latter shall be controlled by the gyrostatic torques of the sphei'es. 
VOL. CXC.—A. •> V 
