Page:The Solar System - Six Lectures - Lowell.djvu/112

 V JUPITER AND HIS COMETS 

describes Jupiter at present; the seething something between sun and world. The planet is either a sun in its senility or an earth in its babyhood, as you are pleased to regard it. For the one state passes by process of development into the other.

Viewed as a sun, it lacks little except light; viewed as a world, it wants everything except that lack of luminosity. It is, as Virgil described another giant, informe ingens cui lumen ademptum. Its density is almost exactly that of the Sun itself. Either, therefore, its bulk is chiefly atmosphere round a kernel of planet, which is Professor Darwin's conclusion, or its smaller mass is offset by its lesser heat, causing a like condensation of the two globes. On the latter supposition, though not luminous, it is still hot. This would bear out and confirm the inference, from the brick-red color between its belts, that its surface is at a red heat.

Almost precisely the same is true of Saturn; the body of that planet, too, being a faint cherry