Page:Popular Science Monthly Volume 51.djvu/378

366 which is the center of the attraction we call gravity; the much greater "lightness" of the materials composing the planet; and the great centrifugal or "throwing-off" force at the equator, due to the rapid rotation, and which would, of course, counteract to some extent the downward pull of gravity—results in making but a slight increase, so that a man weighing one hundred and fifty pounds on the earth would weigh only about six pounds more at Saturn's equator. At the poles, however, the change is more marked, since there is no centrifugal force, and the polar flattening, due to the rapid rotation and consequent bulging at the equator, brings one nearer the center of the planet. In this case the increase would be about thirty-six pounds, and would probably be found somewhat uncomfortable to us.

However, it is by no means certain that the dimensions seen through the telescope are the right ones to consider in this manner. If all we have ever seen of the planet is the outer side of its cloud envelope, it may be that the true surface, provided there is one at all, is far beneath the tops of these rolling cloud masses; and if there is no real surface yet—if the terrible struggle of fire and water for the mastery is still in full sway—no one can tell just what the size of the globe may be when the crust finally forms and the real planetary life begins. This "distended mass of liquid fire" may have shrunk perceptibly by that time.

This also brings up one other interesting query. The spectroscope has proved that the sun and stars are composed of materials with which we are familiar in our laboratories, and Saturn as well as the other planets must be composed of the same chemical elements, though probably with wide variations in combination and distribution. If, then, Saturn were to approach the earth in the density of its composition when it reaches a corresponding stage in its planetary growth, it must shrink to one eighth its present volume, or one half its present diameter. On the other hand, if its size remains anywhere near the present dimensions, we shall almost be forced to the conclusion that this great globe may eventually become one vast ocean—a dreary expanse of water with perhaps only a relatively small solid center, thousands of miles below the surface.

But whatever its future, it will always remain a most interesting object of study, and no one can consider it thoroughly without being inclined to agree with Richard Proctor, that here certainly must be a world "altogether more important in the scheme of creation than the globe on which we live."