_V._ The matters of which man is cognizant escape the senses in gradation. We have, for example, a metal, a piece of wood, a drop of water, the atmosphere, a gas, caloric, electricity, the luminiferous ether. Now we call all these things matter, and embrace all matter in one general definition; but in spite of this, there can be no two ideas more essentially distinct than that which we attach to a metal, and that which we attach to the luminiferous ether. When we reach the latter, we feel an almost irresistible inclination to class it with spirit, or with nihility. The only consideration which restrains us is our conception of its atomic constitution; and here, even, we have to seek aid from our notion of an atom, as something possessing in infinite minuteness, solidity, palpability, weight. Destroy the idea of the atomic constitution and we should no longer be able to regard the ether as an entity, or at least as matter. For want of a better word we might term it spirit. Take, now, a step beyond the luminiferous ether—conceive a matter as much more rare than the ether, as this ether is more rare than the metal, and we arrive at once (in spite of all the school dogmas) at a unique mass—an unparticled matter. For although we may admit infinite littleness in the atoms themselves, the infinitude of littleness in the spaces between them is an absurdity. There will be a point—there will be a degree of rarity, at which, if the atoms are sufficiently numerous, the interspaces must vanish, and the mass absolutely coalesce. But the consideration of the atomic constitution being now taken away, the nature of the mass inevitably glides into what we conceive of spirit. It is clear, however, that it is as fully matter as before. The truth is, it is impossible to conceive spirit, since it is impossible to imagine what is not. When we flatter ourselves that we have formed its conception, we have merely deceived our understanding by the consideration of infinitely rarified matter. _P._ There seems to me an insurmountable objection to the idea of absolute coalescence;—and that is the very slight resistance experienced by the heavenly bodies in their revolutions through space—a resistance now ascertained, it is true, to exist in _some_ degree, but which is, nevertheless, so slight as to have been quite overlooked by the sagacity even of Newton. We know that the resistance of bodies is, chiefly, in proportion to their density. Absolute coalescence is absolute density. Where there are no interspaces, there can be no yielding. An ether, absolutely dense, would put an infinitely more effectual stop to the progress of a star than would an ether of adamant or of iron.