These spectrograms are full of possibilities, and it is not too much to say that chemistry may yet be greatly indebted to the stars. Compounds, the strange unknown substances there revealed by their spectral lines, may be cryptic as yet to us. Some of the elements missing in Mendeléeff’s table may be there, too. Helium was first found in the Sun; coronium still awaits detection elsewhere. So with these spectral lines of the outer planets. It looks as if chemistry had been a thought too previous in making free for others with what should have been their names, Zenon and Uranium. For we may yet have to speak of Dion and Varunium. From the chemical aspect of evolution we pass to its physical side; from the indirectly to the directly visible results. Here again, to learn what happened after the sunlike stage, we must turn to the major planets. For the cooling which induced both physical and chemical change has there progressed less far, inasmuch as a large globe takes longer to cool than a small one. To the largest planets, then, we should look for types of the early planetary stages to-day. Almost as soon as the telescope was directed to Jupiter, among the details it disclosed were the Jovian belts (in the year 1630), dark streaks ruling the planet’s disk parallel to its equator. They are of the first objects advertised as visible in small glasses to-day, vying with the craters in the Moon as purchasable wonders of the sky. As the belts were better and better seen, features came out in them which proved more and more interesting. Cassini, in 1692, noticed that the markings travelled round Jupiter and those nearest his equator the quickest. Sir William Herschel thought them due to Jovian trade-winds, the planet’s swift rotation making up for deficiency of sun; why, does not appear. Modern study of the planet shows that the bright longitudinal layers between the dark belts are unquestionably belts of cloud. Their behavior indicates this, and their intrinsic brightness bears it out. For they are of almost exactly that albedo. Whether they are the kind of cloud with which we are familiar, clouds of water-vapor, we are not yet sure. But whatever their constitution, their conduct is quite other than is exhibited by our own.