The mention of eclipses reminds us, too, of the use which the moon has been in increasing, through them, our knowledge of the physical condition of the sun. If the moon had never intervened to cut off the blinding glare of the solar disc, we should have been to this day left to assume that the sun is all-contained by the dazzling globe that we ordinarily see. But, thanks to the moon’s intervention, we now know that the sun is by no means the mere naked sphere we should have suspected. Eclipses have taught us that it is surrounded by an envelope of glowing gases, and that it has a vast vaporous surrounding, beyond its glowing atmosphere, which appears to be composed of matter streaming away from the sun into surrounding space. With these discoveries still in their infancy, it is impossible to foresee the knowledge to which they will eventually lead, but they can hardly be barren of fruit, and whatever they ultimately teach will be so much insight gained into the sublimest problem that human science has before it—the determination of the source and maintaining power of the light and heat and vivifying agency of the sun. In according our thankful reflections to the moon for these revelations, we must not forget that, should there be inhabitants upon our neighbouring worlds, Mercury, Venus, and Mars, which have no satellites, they, the supposed inhabitants, can gain no such knowledge upon the surroundings of the ruler of the solar system. On the other hand, any rational being who may be supposed to dwell upon Saturn or Jupiter, would, through the intervention of their numerous moons, have, in the latter case especially, far more abundant opportunities of acquiring the knowledge in question than we have.