Thus we are sure that free hydrogen exists in large quantities in the atmospheres of the two outermost planets and most so in the one farthest off. Helium, too, apparently is there, and other gases which in part may be those of long-period stars, decadent suns, in part substances we do not know. From the fact that these bands are not present in the Sun and apparently in no type of stars, we may perhaps infer that the substances occasioning them are not elements but compounds to us unknown. And from the fact that free hydrogen exists there alongside of them, and apparently helium, too, we may further conclude that they are of a lighter order than can be retained by the Earth. But now, we may ask, why should these lighter gases be found where they are? It cannot be in consequence simply of the kinetic theory of gases from which a corollary shows that the heaviest bodies would retain their gases longest, because the strange gases are not apportioned according to the sizes of their hosts. Jupiter, by all odds the biggest in mass, has the least, and Saturn, the next weightiest, the next in amount. Nor can title to such gaseous ownership be lodged in the planet’s present state. For though Jupiter is the hottest and Saturn the next so, the increased mass more than makes up in restraint what increased temperature adds in molecular volatility—as we perceive in the cases of the Sun and Earth. No; their envelopes are increasingly strange because their internal constituents are different, and as hydrogen is most abundant in Neptune, the lightest of all the gases, it is inferable that this planet’s material is lighter. As distance from the Sun determines their atmospheric clothing, so distance decides upon their bodies, too. It was all a case of primogeniture. The light strange matter that constitutes them was so because it came from the outer part of the dismembered parent orb. Neptune the outermost, Uranus the next, then Saturn and Jupiter came in that order from the several successive layers of the pristine body, while the inner planets came from parts of it deeper down. The major planets were of the skin of the dismembered body, we of its lower flesh. Very interesting the study of these curious spectral lines from the outer planets for themselves alone; even more so for what one would hardly have imagined: that they should actually tell us something of the genesis of our whole solar system. They corroborate in so far what the meteorites have to say.