The Metaphysics of a Naturalist 
41 
of Dalton. It is, as history shows^ no great feat of metaphysical 
engineering at times to substitute a new foundation without 
disturbing the superstructure. The theory of a rigid atom, 
besides failing to explain the attraction between atoms, was found 
incompetent to meet the requirements of molecular physics. 
The luminiferous ether was postulated to meet certain of these 
difficulties, Farraday’s electrical ether to escape others, while 
MacCullagh^s rotational ether attempted a mathematical solu- 
tion. A rotational ether depends on the gyrations within for 
its energy. It seems mathematically possible to explain the laws 
of refraction and reflection by such a theory as the’' vortex sponge 
atom, but there are many objections to any form of the vortex 
theory yet presented, aside from the difficulty of mathematically 
expressing the form of motion. Thus, the problem of the density 
of such an atom alone is enough to disturb our confidence in the 
theory. Maxwell has shown that the masses of atoms on the 
vortex theory cannot be explained. Lord Kelvin proposed his 
theory of rigid vortex atoms as far back as 1867, but it has made 
little progress beyond stimulating to other similar attempts. The 
density problem has been simplified by the supposition that, 
just as a rigid sphere moving in a liquid behaves as though its 
mass were increased by half the displaced liquid, so the atom has 
an effective mass greatly increased by the effect of the velocity 
on the surrounding medium. Nevertheless we see that an explana- 
tion requiring to be so amended is no explanation at all, for we 
approach no nearer to the ultimate by interposing an interme- 
diary and incongruous postulate between phenomena and the 
unknown ultimate. J. J. Thomson has shown how vortex rings 
enable us to understand the laws of a perfectly elastic atom, 
but no form of vortex atom has yet offered a satisfactory explana- 
tion of gravitation, which is really the crucial point in the dis- 
cussion. 
But we must not forget that, as already stated, all these 
theories require an elastic ether, or, as Dr, Hicks himself admits, 
^^a primitive perfect fluid. However, I am assured by a well- 
known mathematical physicist in a recent letter that it is still con- 
sidered that the ether is not imponderable, but has a certain 
small weight. If so, it follows that ether cannot be perfectly 
elastic and our search begins de novo. 
Now, the one thing that seems evident in the maze of conflicting 
