Then, to vary the theme, we find charming inhabitants of other worlds represented as coming down to the earth and sojourning for a time on our dull planet, to the delight of susceptible successors of father Adam, who become, henceforth, ready to follow their captivating visitors to the ends of the universe.

In short, writers of fiction have already established interplanetary communication to their entire satisfaction, thus vastly and indefinitely enlarging the bounds of romance, and making us so familiar with the peculiarities of our remarkable brothers and sisters of Mars, Venus, and the moon, that we can not help feeling, notwithstanding the many divergences in the descriptions, that we should certainly recognize them on sight wherever we might meet them.

But the subject is by no means abandoned to the tellers of tales and the dreamers of dreams.  Men of science, also, eagerly enter into the discussion of the possibilities of other worlds, and become warm over it.

Around Mars, in particular, a lively war of opinions rages.  Not all astronomers have joined in the dispute—­some have not imagination enough, and some are waiting for more light before choosing sides—­but those who have entered the arena are divided between two opposed camps.  One side holds that Mars is not only a world capable of having inhabitants, but that it actually has them, and that they have given visual proof of their existence and their intelligence through the changes they have produced upon its surface.  The other side maintains that Mars is neither inhabited nor habitable, and that what are taken for vast public works and engineering marvels wrought by its industrious inhabitants, are nothing but illusions of the telescope, or delusions of the observer’s mind.  Both adduce numerous observations, telescopic and spectroscopic, and many arguments, scientific and theoretic, to support their respective contentions, but neither side has yet been able to convince or silence the other, although both have made themselves and their views intensely interesting to the world at large, which would very much like to know what the truth really is.

And not only Mars, but Venus—­the beauteous twin sister of the earth, who, when she glows in the evening sky, makes everybody a lover of the stars—­and even Mercury, the Moor among the planets, wearing “the shadowed livery of the burnished sun,” to whom he is “a neighbor and near bred,” and Jupiter, Saturn, and the moon itself—­all these have their advocates, who refuse to believe that they are lifeless globes, mere reflectors of useless sunshine.

The case of the moon is, in this respect, especially interesting, on account of the change that has occurred in the opinions held concerning its physical condition.  For a very long time our satellite was confidently, and almost universally, regarded as an airless, waterless, lifeless desert, a completely “dead world,” a bare, desiccated skull of rock, circling about the living earth.