IV. The consistency of ether is also peculiar, on our hypothesis, and different from that of ponderable matter. It is neither gaseous, as some conceive, nor solid, as others suppose; the best idea of it can be formed by comparison with an extremely attenuated, elastic, and light jelly.
V. Ether may be called imponderable matter in the sense that we have no means of determining its weight experimentally. If it really has weight, as is very probable, it must be so slight as to be far below the capacity of our most delicate balance. Some physicists have attempted to determine its weight by the energy of the light-waves, and have discovered that it is some fifteen trillion times lighter than atmospheric air; on that hypothesis a sphere of ether of the size of our earth would weigh at least two hundred and fifty pounds(?).
VI. The etheric consistency may probably (in accordance with the pyknotic theory) pass into the gaseous state under certain conditions by progressive condensation, just as a gas may be converted into a fluid, and ultimately into a solid, by lowering its temperature.
VII. Consequently, these three conditions of matter may be arranged (and it is a point of great importance in our monistic cosmogony) in a genetic, continuous order. We may distinguish five stages in it: (1) the etheric, (2) the gaseous, (3) the fluid, (4) the viscous (in the living protoplasm), and (5) the solid state.
VIII. Ether is boundless and immeasurable, like the space it occupies. It is in eternal motion; and this specific movement of ether (it is immaterial whether we conceive it as vibration, strain, condensation, etc.), in reciprocal action with mass-movement (or gravitation), is the ultimate cause of all phenomena.
“The great question of the nature of ether,” as Hertz justly calls it, includes the question of its relation to ponderable matter; for these two forms of matter are not only always in the closest external contact, but also in eternal, dynamic, reciprocal action. We may divide the most general phenomena of nature, which are distinguished by physics as natural forces or “functions of matter,” into two groups; the first of them may be regarded mainly (though not exclusively) as a function of ether, and the second a function of ponderable matter—as in the following scheme which I take from my Monism:
| Ether—Imponderable. | Mass—Ponderable. |
|---|---|
| 1. Consistency: Etheric (i.e., neither gaseous nor fluid, nor solid). | 1. Consistency: Not etheric (but gaseous, fluid, or solid). |
| 2. Structure: Not atomistic, not made up of separate particles (atoms), but continuous. | 2. Structure: Atomistic, made up of infinitesimal, distinct particles (atoms) discontinuous. |
| 3. Chief Functions: Light, radiant heat, electricity, and magnetism. | 3. Chief Functions: Gravity, inertia, molecular heat, and chemical affinity. |
The two groups of functions of matter, which we have opposed in this table, may, to some extent, be regarded as the outcome of the first “division of labor” in the development of matter, the “primary ergonomy of matter.” But this distinction must not be supposed to involve an absolute separation of the two antithetic groups; they always retain their connection, and are in constant reciprocal action. It is well known that the optical and electrical phenomena of ether are closely connected with mechanical and chemical changes in ponderable elements; the radiant heat of ether may be directly converted into the mechanical heat of the mass; gravitation is impossible unless the ether effects the mutual attraction of the separated atoms, because we cannot admit the idea of an actio in distans. In like manner, the conversion of one form of energy into another, as indicated in the law of the persistence of force, illustrates the constant reciprocity of the two chief types of substance, ether and mass.
The great law of nature, which, under the title of the “law of substance,” we put at the head of all physical considerations, was conceived as the law of “the persistence of force” by Robert Meyer, who first formulated it, and Helmholtz, who continued the work. Another German scientist, Friedrich Mohr, of Bonn, had clearly outlined it in its main features ten years earlier (1837). The old idea of force was, after a time, differentiated by modern physics from that of energy, which was at first synonymous with it. Hence the law is now usually called the “law of the persistence of energy.” However, this finer distinction need not enter into the general consideration, to which I must confine myself here, and into the question of the great principle of the “persistence of substance.” The interested reader will find a very clear treatment of the question in Tyndall’s excellent paper on “The Fundamental Law of Nature,” in his Fragments of Science. It fully explains the broad significance of this profound cosmic law, and points out its application to the main problems of very different branches of science. We shall confine our attention to the important fact that the “principle of energy” and the correlative idea of the unity of natural forces, on the basis of a common origin, are now accepted by all competent physicists, and are regarded as the greatest advance of physics in the nineteenth century. We now know that heat, sound, light, chemical action, electricity, and magnetism are all modes of motion. We can, by a certain apparatus, convert any one of these forces into another, and prove by an accurate measurement that not a single particle of energy is lost in the process.