Separated from all these impurities, the crystal becomes clear and limpid." This experiment is especially the true image of what Faraday was as a metaphysician. For him nothing had so great a charm as those serene transparent regions, in which science, cleared of impurities, appeared to his great mind in all the glory of its power and splendor. He yielded himself to it with absolute abandonment. He particularly loved to dwell upon the problem which is now engaging us: "What do we know of an atom apart from force?" he exclaims. "You conceive a nucleus which may be called a, and you surround it with forces which may be called m; to my mind your a or nucleus vanishes, and substance consists in the energy of m. In fact, what notion can we form of a nucleus independent of its energy?" As he holds, matter fills all space, and gravitation is nothing else than one of the essentially constitutive forces of matter, perhaps even the only one. An eminent chemist, Henry Saint-Claire Deville, lately declared that, when bodies deemed to be simple combine with one another, they vanish, they are individually annihilated. For instance, he maintains that in sulphate of copper there is neither sulphur, nor oxygen, nor copper. Sulphur, oxygen, and copper, are composed, each of them, by a distinct system of definite vibrations of one energy, one single substance. The compound, sulphate of copper, answers to a different system, in which the motions are confounded that would produce the respective individualities of its elements, sulphur, oxygen, and copper. Moreover, Berthelot long ago expressed himself in exactly the same manner. As long ago as 1864 that savant said that the atoms of simple bodies might be composed of one and the same matter, distinguished only by the nature of the motions set up in it. This decisive saying a great number of savants and philosophers in France and abroad have repeated and are still repeating, with good reason, as the expression of a solid truth.
If the smallest parts which we can imagine and distinguish in bodies differ from each other only by the nature of the motions to which they are subjected, if motion alone rules and determines the variety of different attributes which characterizes these atoms, if in a word the unity of matter exists—and it must exist—what is this fundamental and primary matter whence all the rest proceed? How shall we represent it to our minds? Every thing leads to the belief that it is not essentially distinguished from the ether, and consists in atoms of ether more or less strongly held together. It is objected that the ether is imponderable; but that is an unfounded objection. Doubtless it cannot be weighed; to do that we must compare a space filled with ether to a space empty of ether; and we are evidently unable to isolate this subtle agent, whose particles counterpoise each other with perfect equilibrium throughout the universe. Yet many facts attest its prodigious elasticity. A flash of lightning is nothing more than a disturbance of equilibrium in the ether, yet no one will deny that
