[Footnote A: Vol. II, p. 184.]
[Footnote B: Heat, A Mode of Motion, Tyndall, 6th ed., p. 38.]
The wonderful developments of the last century, in electricity and magnetism, led to much speculation concerning the nature of the subtle electrical and magnetic forces. The most popular theories for many years were those that presupposed various electrical and magnetic fluids, which could be collected, conducted, dispersed and otherwise controlled. In 1867, the eminent English mathematician, Clerk Maxwell, proposed the theory that electrical and magnetic phenomena were simply peculiar motions of the ether, bearing definite relationship to light waves. Later researches, one result of which is the now famous Roentgen or X-rays, have tended to confirm Maxwell's theory. A recent text-book on physics, of unquestioned authority,[A] states that the ether theory of electricity and magnetism is now susceptible of direct demonstration; and another eminent authority frankly states that "when we explain the nature of electricity, we explain it by a motion of the luminiferous ether."[B]
[Footnote A: Lehrbuch der Physik, Riecke, (1896), 2ter Band, p. 315.]
[Footnote B: Popular Lectures and Addresses, Kelvin (1891) Vol. 1, page 334.]
Other recent discoveries have hinted at the possibility of matter itself being only the result of peculiar forms of this all-pervading substance, the luminiferous ether. The properties of the element radium, and other radioactive elements, as at present understood, suggest the possibility of a better understanding of the nature of the ether, and of its relation to the world of phenomena.
[Sidenote: The existence of the ether is a certainty of science.]
That the present knowledge of the world of science compels a faith in an all-pervading substance, of marvelous properties, and of intimate relationship to all forms of energy, is shown by the following quotations from Lord Kelvin, who is generally regarded as the world's greatest physicist: "The luminferous ether, that is the only substance we are confident of in dynamics. One thing we are sure of, and that is the reality and substantiality of the luminiferous ether." "What can this luminiferous ether be? It is something that the planets move through with the greatest ease. It permeates our air; it is nearly in the same condition, so far as our means of judging are concerned, in our air and in the interplanetary space." "You may regard the existence of the luminiferous ether as a reality of science." "It is matter prodigiously less dense than air—of such density as not to produce the slightest resistance to any body going through it."[A]
[Footnote A: Kelvin's Lectures, Vol. 1, pp. 317, 334, 336, 354.]
The theory of the ether is one of the most helpful assumptions of modern science. By its aid the laws of energy have been revealed. There is at the present time no grander or more fundamental doctrine in science than that of the ether. The nature of the ether is, of course, far from being clearly understood, but every discovery in science demonstrates that the hypothetical ether stands for an important reality of nature. Together with the doctrines of the indestructibility of matter and energy, the doctrine of the ether welds and explains all the physical phenomena of the universe.