Now, so far as astronomy has revealed the condition of other worlds, almost all of them appear to be passing through those preparatory changes which the earth underwent previous to man's creation. What are the unresolvable nebulæ and most of the comets also, but intensely heated vapor and gas? What is the sun but a molten globe, or perhaps gaseous matter condensed so as to possess almost the density of water? The planets beyond Mars, also, (excluding the asteroids,) appear to be in a liquid condition, but not from heat, and therefore may be composed of water, or some fluid perhaps lighter than water; or at least be covered by such fluid. Moreover, so great is their distance from the sun, that his light and heat could not sustain organic beings such as exist upon the earth. Of the inferior planets, Mercury is so near the sun that it would be equally unfit for the residence of such beings. Mars, Venus, and the Moon, then, appear to be the only worlds known to us capable of sustaining a population at all analogous to that upon earth. But of these, the Moon appears to be merely a mass of extinguished volcanos, with neither water nor atmosphere. It has proceeded farther in the process of refrigeration than the earth, because it is smaller; and in its present state, is manifestly unfit for the residence either of rational or irrational creatures. So that we are left with only Mars and Venus in the solar system to which the common arguments in favor of other worlds being inhabited, will apply. But are not the fixed stars the suns of other systems? We will thank those who think so, to read the chapter in this work that treats of the fixed stars, and we presume they will be satisfied that at least many of these bodies exhibit characters quite irreconcilable with such an hypothesis. And if some are not central suns, the presumption that the rest are, is weakened, and we must wait till a greater perfection of instruments shall afford us some positive evidence, before we know whether our solar system is a type of any others.