As one passed toward the north, or the south, pole he would see the upper part of the arch of the rings gradually sink toward the horizon until at length, somewhere in the neighborhood of the polar circle, it would finally disappear, hidden by the round shoulder of the great globe.
URANUS, NEPTUNE, AND THE SUSPECTED ULTRANEPTUNIAN PLANET What has been said of Jupiter and Saturn applies also to the remaining members of the Jovian group of planets, Uranus and Neptune, viz., that their density is so small that it seems probable that they can not, at the present time, be in a habitable planetary condition.

All four of these outer, larger planets have, in comparatively recent times, been solar orbs, small companions of the sun.

The density of Uranus is about one fifth greater than that of water, and slightly greater than that of Neptune.

Uranus is 32,000 miles in diameter, and Neptune 35,000 miles.
Curiously enough, the force of gravity upon each of these two large planets is a little less than upon the earth.

This arises from the fact that in reckoning gravity on the surface of a planet not only the mass of the planet, but its diameter or radius, must be considered.