Not including the rings in the calculation, Saturn exceeds the earth in size 760 times.  The addition of the rings would not, however, greatly alter the result of the comparison, because, although the total surface of the rings, counting both faces, exceeds the earth’s surface about 160 times, their volume, owing to their surprising thinness, is only about six times the volume of the earth, and their mass, in consequence of their slight density, is very much less than the earth’s, perhaps, indeed, inappreciable in comparison.

Saturn’s mean diameter is 73,000 miles, and its polar compression is even greater than that of Jupiter, a difference of 7,000 miles—­almost comparable with the entire diameter of the earth—­existing between its equatorial and its polar diameter, the former being 75,000 and the latter 68,000 miles.

We found the density of Jupiter astonishingly slight, but that of Saturn is slighter still.  Jupiter would sink if thrown into water, but Saturn would actually float, if not “like a cork,” yet quite as buoyantly as many kinds of wood, for its mean density is only three quarters that of water, or one eighth of the earth’s.  In fact, there is no known planet whose density is so slight as Saturn’s.  Thus it happens that, notwithstanding its vast size and mass, the force of gravity upon Saturn is nearly the same as upon our globe.  Upon visiting Venus we should find ourselves weighing a little less than at home, and upon visiting Saturn a little more, but in neither case would the difference be very important.  If the relative weight of bodies on the surfaces of planets formed the sole test of their habitability, Venus and Saturn would both rank with the earth as suitable abodes for men.

But the exceedingly slight density of Saturn seems to be most reasonably accounted for on the supposition that, like Jupiter, it is in a vaporous condition, still very hot within—­although but slightly, if at all, incandescent at the surface—­and, therefore, unsuited to contain life.  It is hardly worth while to speculate about any solid nucleus within, because, even if such a thing were possible, or probable, it must lie forever hidden from our eyes.  But if we accept the theory that Saturn is in an early formative stage, and that, millions of years hence, it may become an incrusted and habitable globe, we shall, at least, follow the analogy of what we believe to have been the history of the earth, except that Saturn’s immense distance from the sun will always prevent it from receiving an amount of solar radiation consistent with our ideas of what is required by a living world.  Of course, since one can imagine what he chooses, it is possible to suppose inhabitants suited to existence in a world composed only of whirling clouds, and a poet with the imagination of a Milton might give us very imposing and stirring images of such creatures and their chaotic surroundings, but fancies like these can have no basis in human experience, and consequently can make no claim upon scientific recognition.