known facts of astronomy, only allowing the fancy to have free play where science is, and must be, unable, in its present state, to answer the questions here considered. If there are any statements which are found to be irreconcilable with any of the recent discoveries of inductive science, I shall be much obliged to any scientific reader to draw my attention to them, and they shall be corrected in a future edition.
It will be noticed by the reader that, to give it more human interest, and also to ventilate some practical subjects, there are two Utopias in this book—the one in which there is a speculation as to a perfect society of perfect happiness, such as may be regarded as a meditation on the possible joys of a future state; the other a more practical Utopia, implying the tendencies of human progress, and suggesting improvements for human society as it now exists. The other worlds beside these two (Venus and Mars) have no special earth-lesson to teach; they are little more than bold deductions from observations or probabilities suggested by them.
I have by no means assumed, as some extreme partisans of the habitability of other worlds are wont to do, that all the planets are inhabited. I rather suppose that Earth at
