The first difficulty with this theory is to explain how, if the hydrogen wiggled off in this unceremonious manner, it ever wiggled on. There is no objection to a gait of this rapidity, however; it is highly creditable, in fact; but we have a right to expect some degree of consistency in even so light-headed a body as hydrogen gas. The article quoted thus continues: "If the mass of the earth were very much larger than it is, then the velocities with which the molecules of hydrogen wend their way would never be sufficiently high to enable them to quit the earth altogether, and consequently we might in such a case expect to find our atmosphere largely charged with hydrogen." It will be seen that, according to this theory, hydrogen is able to achieve a speed of seven miles per second under exceptional excitement, and that this molecular velocity is just enough, and no more than enough, to give it egress. We know that Jupiter's mass is three hundred times as great as that of the earth, and the attraction of gravity is so powerful on the surface of that planet that, as the writer just quoted says, "Walking, or even standing, would involve the most fearful exertion, while rising from bed in the morning would be a difficult, indeed, probably, an impossible, process." We also know that the atmosphere of this planet is laden with enormous clouds floating at various altitudes and with incessant movements. We are told that "the molecular speed of aqueous vapor averages only one-third of that attained by the molecules of hydrogen." Of course, on the planet Jupiter, hydrogen would have no chance of escape at all: it would just have to stay and take it, like the rest of us. Jupiter must thus have an atmosphere like our own, except that it is "largely charged with hydrogen." Of the clouds upon this planet, Professor Ball says, "In fact, the longer we look at Jupiter the more we become convinced that the surface of the planet is swathed with a mighty volume of clouds so dense and so impenetrable that our most powerful telescopes have never yet been able to pierce through them down to the solid surface of the planet." With the densities, molecular velocities, and specific gravity of the oxygen, nitrogen, and the hydrogen, with which latter the atmosphere of Jupiter must be "largely charged," as it is said, it is difficult to understand how such enormous clouds of aqueous vapors, themselves composed of oxygen, which is a very slow-footed gas, and hydrogen, could travel about with such facility; we ought to find them packed down like London fog, to say the least, upon the surface of that planet, with the supernatant gases all adrift overhead. Jupiter is a hot body; it has not yet cooled down; and if it is provided with volcanoes, such as its great red spot and the analogies of the earth and moon would suggest, we can tell pretty nearly what would have happened long ago with a Jovian atmosphere like ours; but "largely charged with hydrogen," if we compare it with,