---------------------------------+------------------------------------- ETHER--Imponderable. | MASS--Ponderable. ---------------------------------+------------------------------------- | 1. _Consistency_: | 1. _Consistency_: | Etheric (_i.e._, neither | Not etheric (but gaseous, fluid, gaseous nor fluid, nor solid). | or solid). | 2. _Structure_: | 2. _Structure_: | Not atomistic, not made up of | Atomistic, made up of infinitesimal, separate particles (atoms), but | distinct particles (atoms) continuous. | discontinuous. | 3. _Chief Functions_: | 3. _Chief Functions_: | Light, radiant heat, electricity,| Gravity, inertia, molecular heat, and magnetism. | 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.
The sum-total of force or energy in the universe remains constant, no matter what changes take place around us; it is eternal and infinite, like the matter on which it is inseparably dependent. The whole drama of nature apparently consists in an alternation of movement and repose; yet the bodies at rest have an inalienable quantity of force, just as truly as those that are in motion. It is in this movement that the potential energy of the former is converted into the kinetic energy of the latter. "As the principle of the persistence of force takes into account repulsion as well as attraction, it affirms that the mechanical value of the potential energy and the kinetic energy in the material world is a constant quantity. To put it briefly, the force of the universe is divided into two parts, which may be mutually converted, according to a fixed relation of value. The diminution of the one involves the increase of the other; the total value remains unchanged in the universe." The potential energy and the actual, or kinetic, energy are being continually transformed from one condition to the other; but the infinite sum of force in the world at large never suffers the slightest curtailment.
Once modern physics had established the law of substance as far as the simpler relations of inorganic bodies are concerned, physiology took up the story, and proved its application to the entire province of the organic world. It showed that all the vital activities of the organism--without exception--are based on a constant "reciprocity of force" and a correlative change of material, or metabolism, just as much as the simplest processes in "lifeless" bodies. Not only the growth and the nutrition of plants and animals, but even their functions of sensation and movement, their sense-action and psychic life, depend on the conversion of potential into kinetic energy, and _vice versâ_. This supreme law dominates also those elaborate performances of the nervous system which we call, in the higher animals and man, "the action of the mind."
Our monistic view, that the great cosmic law applies throughout the whole of nature, is of the highest moment. For it not only involves, on its positive side, the essential unity of the cosmos and the causal connection of all phenomena that come within our cognizance, but it also, in a negative way, marks the highest intellectual progress, in that it definitely rules out the three central dogmas of metaphysics--God, freedom, and immortality. In assigning mechanical causes to phenomena everywhere, the law of substance comes into line with the universal law of causality.
