The 'Sub-Mechanics of the Universe' are here made to depend upon the fitting together of ineffably small, ideally rigid grains. A misfit gives rise to matter, which might hence be defined as 'ether out of joint'; and the misfit can be propagated endlessly from one range of granules to the next. This propagation through the ether of an abnormal arrangement of its constituent particles, without any transference of the particles themselves, explains the phenomena of matter in motion. A concrete existence belongs to the ether alone. It is composed of round aboriginal atoms, the diameters of which measure the seven hundred thousand millionth part of the wave-length of violet light.[81] They are packed closely together, yet not so closely but that free paths are left to them averaging in length the four hundred thousand millionth part of their diameters.
This inconceivably small relative motion suffices, nevertheless, to render the medium elastic; is, indeed, 'the only cause of elasticity in the universe, and hence is the prime cause of the elasticity of matter.' The medium so formed is ten thousand times denser than water; it exerts a mean pressure of 750,000 tons on the square inch; the coefficient of its transverse elasticity is 9 + 1024 (in C.G.S. units); which gives a velocity of transmission identical with that of light for vibrations of the same type, while longitudinal waves are propagated 2·4 times more rapidly. The scheme further includes a plausible rationale of gravity and of electrical effects; so that there is much to warrant the claim of its author to have excogitated 'the one and only conceivable purely mechanical system capable of accounting for all the physical evidence, as we know it, in the universe.'
The machine, to be sure, lacks motive power; but that is a want which no human ingenuity can supply. Its source is obscured in the primal mystery of creation. And as regards the preliminary assumptions required for the constitution of an atomic ether, inclined though we might be to cavil at them, we should, perhaps, act more wisely in following Dr. Larmor's advice by abstaining from attempts to explain 'the simple group of relations which have been found to define the activity of the ether. We should rather rest satisfied,' he tells us, 'with having attained to their exact dynamical correlation, just as geometry explores or correlates, without explaining, the descriptive and metric properties of space.'[82] Yet one cannot help remarking that the properties of space are not ordinarily modified to suit the needs of demonstration, while those of the ethereal medium are varied at the arbitrary discretion of rival cosmogonists. In the future, when they come to be more clearly ascertained, they will, perhaps, form the basis of a genuine new science. Already, the study of ethereal physics excites profound interest and attention. Nor is it possible to ignore the gathering indications that it will impose qualifications upon principles consecrated by authority and hitherto regarded as fundamental.
The grand modern tenet of the conservation of energy, for example, may need a gloss; it may prove to be admissible only with certain restrictions. The second bulwark of the scientific edifice is even more seriously undermined. For the 'strain theory' of atomic constitution necessarily includes the conception of opposite distortions corresponding to positive and negative electricity. And the further inference lies close at hand that these, by combining, may neutralize one another. The coalescence, then, of a positive and negative electron should result in the smoothing out of the complementary strains they stand for; and there would ensue the annihilation of a pair of the supposed ultimates of matter. The event might be called the statical equivalent of the destruction of light through interference. That its possibility should be contemplated even by the most adventurous thinkers is a circumstance fraught with meaning as to the subversive tendencies of recent research.
Already, in May, 1902, Professor J. A. Fleming[83] pointed out that 'if the electron is a strain-centre in the ether, then corresponding to every negative electron there must be a positive one. In other words, electrons must exist in pairs of such kind that their simultaneous presence at one point would result in the annihilation of both of them.' The consequence thus viewed in the abstract finds concrete realization, if Mr. Jeans's suggestion be adopted,[84] in the processes of radio-activity, which possibly consist 'in an increase of material energy at the expense of the destruction of a certain amount of matter. There would, therefore, be conservation neither of mass nor of material energy.'
No longer ago than at the opening of the present century such notions would have been scouted as extravagant and paradoxical; now there is no escape from giving them grave and respectful consideration. Scientific reason has ceased to be outraged by hypotheses regarding the disappearance of mass and the development of energy. Mass and energy may, after all, be interchangeable; they are, at any rate, kept less rigidly apart in our meditations than used formerly to be the case. Nor can we assert with any confidence that partial subsidences into or emergences from the surrounding medium are for either a sheer impossibility; the universal framework, on the contrary, presents itself to us in the guise of an iridescent fountain leaping upward from, and falling back towards, the ethereal reservoir.
To the very brink of that mysterious ocean the science of the twentieth century has brought us; and it is with a thrill of wondering awe that we stand at its verge and survey its illimitable expanse. The glory of the heavens is transitory, but the impalpable, invisible ether inconceivably remains. Such as it is to-day, it already was when the Fiat Lux was spoken; its beginning must have been coeval with that of time. Nothing or everything, according to the manner in which it is accounted of, it is evasive of common notice, while obtrusive to delicate scrutiny. Its negative qualities are numerous and baffling. It has no effect in impeding motion; it does not perceptibly arrest, absorb, or scatter light; it pervades, and may even share in the displacements of gross matter; yet its motion (if it do move), is without effect on the velocity of light.
Looking, however, below the surface of things, we find the semi-fabulous quintessence to be unobtrusively doing all the world's work. It embodies the energies of motion; is, perhaps, in a very real sense, the true primum mobile; the potencies of matter are rooted in it; the substance of matter is latent in it; universal intercourse is maintained by means of the ether; cosmic influences can be exerted only through its aid; unfelt, it is the source of solidity; unseen, it is the vehicle of light; itself non-phenomenal, it is the indispensable originator of phenomena. A contradiction in terms, it points the perennial moral that what eludes the senses is likely to be more permanently and intensely actual than what strikes them.