Now, transverse waves can exist only in rigid (solid) bodies. The universal ether of space, referred to in the text-books, must—for reasons which I need not discuss here—be a solid body of a rigidity much greater than that of steel, while at the same time possessing a very great elasticity so that bodies (such as the planets) moving through it meet with no resistance, no friction. The electron theory of Lorentz, Larmor, Thomson, Lodge and others is based upon the assumption that such a _plenum_, or medium, is a real substance. As a matter of fact, it is not known that any such medium (or ether) does exist, and it is now recognized that while light is a _wave_, a periodic phenomenon, like an alternating current, it is not necessarily a wave _motion_ of something or in something, any more than it is necessary to assume the alternating current or voltage wave to be a motion of matter. Electrical engineers make no assumption regarding the existence of an ether filling all space and interpenetrating all matter—have no need for an ether as the hypothetical carrier of the electric wave. And just so the physicist of today has no real need for the classical assumption that the light-wave is a wave motion of or in something of great rigidity yet highly elastic and frictionless, filling all space. Light is now known to be a high-frequency electromagnetic wave, and cannot logically be considered as a wave motion of a hypothetical ether. “The ether thus vanishes, following the phlogistin and other antiquated conceptions.”[2] As Prof. A. S. Eddington remarks in his “Report on the Relativity Theory of Gravitation” (1920), “Light does not cause electromagnetic oscillations; it _is_ the oscillations.” We know nothing whatever about the so-called ether of space; but we can formulate very clearly “The Principles of Electricity” without the aid of that hypothesis.[3] FOOTNOTES: [1] If a light piece of iron is placed near a magnet, it moves to the magnet and clings to it; but if the magnet is the lighter of the two bodies, it moves toward the piece of iron. [2] Steinmetz, Dr. Charles P., “Four Lectures on Relativity and Space,” Pages 21-22, London and New York, 1923. See Lecture II, “Conclusions from the Relativity Theory,” Pages 12-45. See also, Campbell, Dr. Norman R., “Modern Electrical Theory. Supplementary Chapters: Relativity,” Cambridge University Press, 1923. CHAPTER 2 MAGNETIC PHENOMENA It was long ago observed that if glass is rubbed by silk, or a piece of sealing-wax or hard rubber by fur or wool, an effect occurs similar to that noted by Thales when amber is rubbed by similar materials—i. e., light bodies such as bits of dry paper, pith, etc., will cling to the surface of the substance. After coming in contact with the attracting substance, the bits of paper, straw, etc., are then repelled.