28. The numerous tribe of small bodies, which revolve between Jupiter and Mars, do not admit of much of the kind of reasoning, which we have applied to the larger planets. They have, with perhaps one exception (Vesta) no disk of visible magnitude; they are mere dots, and we do not even know that their form is spherical. The near coincidence of their orbits has suggested, to astronomers, the conjecture that they have resulted from the explosion of a larger body, and from its fracture into fragments. Perhaps the general phenomena of the universe suggest rather the notion of a collapse of portions of sidereal matter, than of a sudden disruption and dispersion of any portion of it; and these small bodies may be the results of some imperfectly effected concentration of the elements of our system; which, if it had gone on more completely and regularly, might have produced another planet, like Mars or Venus. Perhaps they are only the larger masses, among a great number of smaller ones, resulting from such a process: and it is very conceivable, that the meteoric stones which, from time to time, have fallen upon the earth's surface, are other results of the like process:--bits of planets which have failed in the making, and lost their way, till arrested by the resistance of the earth's atmosphere. A remarkable circumstance in these bodies is, that though thus coming apparently from some remote part of the system, they contain no elements but such as had already been found to exist in the mass of the earth; although some substances, as nickel and chrome, which are somewhat rare in the earth's materials, are common parts of the composition of meteoric stones. Also they are of crystalline structure, and exhibit some peculiarities in their crystallization. Such as these strange visitors are, they seem to show that the other parts of the solar system contain the same elementary substances, and are subject to the same laws of chemical synthesis and crystalline force, which obtain in the terrestrial region. The smallness of these specimens is a necessary condition of their reaching us; for if they had been more massive, they would have followed out the path of their orbits round the sun, however eccentric these might be. The great eccentricity of the smaller planets, their great deviation from the zodiacal path, which is the highway of the large planets, their great number, probably by no means yet exhausted by the discoveries of astronomers; all fall in with the supposition that there are, in the solar system, a vast multitude of such abnormal planetoidal lumps. As I have said, we do not even know that they are approximately spherical; and if they are of the nature of meteoric stones, they are mere crude and irregularly crystallized masses of metal and earth. It will therefore, probably, be deemed unnecessary to give other reasons why these planetoids are not inhabited. But if it be granted that they are