Broad reaches of black and empty space! Where are they? Perhaps nowhere. We are very apt, in our ignorance, to imagine that where we see nothing, there must of necessity be nothing. But, for aught we know, the whole Solar System, not to speak of sky-depths lying beyond, may be bright with reflecting bodies great and small, from the mighty Jupiter down to the fine diamond-dust of countless meteorites. In this earth of ours we find no emptiness. Closer and closer examination with the microscope only shows tinier and yet tinier wonders of form and life, each perfect in finish. Not of form only, but of _life_. How about that matter as regards the Solar System? Is our little world the one only spot in God’s great universe which teems with life? Are all other worlds mere barren, empty wastes? Surely not. We may safely conclude that life of one kind or another has been, is, or will be, upon our brother and sister worlds. The same reasoning may be used for the distant stars--those millions of suns lying beyond reach of man’s unassisted eyes. Are they formed in vain? Do their beams pour uselessly into space, carrying light, warmth, and life-giving power to nothing? Surely around many of them, as around our sun, must journey worlds; and not only worlds, but worlds containing life. We shall have to speak of this matter again as we go on. Whether men and women like ourselves could live on the other planets is another question. In some cases it looks doubtful, in some it would seem to be impossible. But the endless variety of life on this earth--life on land, life in the air, life in water, life underground, life in tropical heat, life in arctic cold--forbids us in anywise to be positive as to what may or may not be. If no animals that we know could exist there, animals that we do not know might be found instead. Any one of the planets may, and very likely does, abound with life. Nay, the very meteorites themselves, before they catch fire and burn in our air, _may_ be the homes of tiny animalcula, altogether different from anything we see on earth. We can not fancy life without air, but neither could we fancy life in water, if we had not seen and known it to be possible.