earth, is in incessant movement. There is a constant flow, and the wisdom of the Creator is seen, rather in the exquisite rhythm of movement, than in the rigid collocation of the material world. We see only a few spokes of the great wheel of the universe; and what appears to be a destructive breach of continuity, may be only the completed part of a mighty cycle.
As to the purpose served by comets, the odd fancy of Newton, that they are intended to serve as fuel to the sun, is again revived, and revived by our ablest philosophers. It is held, in connexion with the dynamical theory of heat, that the sun's heat and light must be exhausted, unless supplied with fuel, and comets are held as part of the fuel destined to keep the central fire burning. It is supposed that there are zones of meteoric matter round the sun, of which the zodiacal light may be one, which supply the sun with the needful fuel. And some careful observers state, that they have actually seen large bodies plunge into the luminous atmosphere, just as a large block of coal is thrown into the furnace by the stoker. These bodies are not supposed to act precisely as fuel, though they keep up the heat. In the practice of the Armstrong guns, it was found when a bolt was lodged in the sides of the gunboat serving as target, that it could not be touched with the hand on account of the great heat—the arrested motion being converted into heat. So the meteorites and comets are supposed to communi-
