But may not the stars have planets revolving round them, forming solar systems similar to our own? As they are evidently suns shining by inherent light, may they not form centres of planetary systems? In the case of those stars having spectra differing from the solar spectrum, we can not speak with any confidence; but for those which show spectra similar to that of our sun, and having, therefore, probably a similar chemical constitution, the existence of planets revolving round them seems from analogy very probable. I refer to _single_ stars, that is stars which have no telescopic close companion; for the double stars may, perhaps, form systems differently constituted. In any case these binary systems would not be strictly comparable with ours, for the sun is certainly a single star. Whether systems of planets really revolve round the stars referred to, is a question which, unfortunately, can not be decided by observation. If a planet equal in size to the “giant planet,” Jupiter, were revolving round the nearest star—Alpha Centauri—at the same distance from that star that Jupiter is from the sun, it would be utterly invisible in our largest telescopes. The invisibility of planets circling round the stars is therefore no proof whatever of their non-existence. Each star of the solar type may possibly be attended by a retinue of planets which may, perhaps, remain forever invisible in the largest telescopes which man can construct. We can, therefore, draw our conclusions only from analogy. If other suns exist resembling our own sun in chemical constitution, which we know to be a fact, is it not reasonable to suppose that they also form centres of planetary systems similar to the Solar System? “Consult with reason, reason will reply, Each lucid point which glows in yonder sky, Informs a system in the boundless space, And fills with glory its appointed place; With beams unborrowed brighten other skies, And worlds to the unknown with heat and light supplies.” The suns, which we call stars, were clearly not created for our benefit. They are of very little practical use to the earth’s inhabitants. They give us very little light; an additional small satellite—one considerably smaller than the moon—would have been much more useful in this respect than the millions of suns revealed by the telescope. They must, therefore, have been formed for some other purpose.