Page:Popular Science Monthly Volume 51.djvu/371

Rh, we never yet have caught a glimpse, so far as known, of the real surface, whatever that surface may be. The rolling cloud masses completely envelop the planet and shut it out entirely from the sun's light.

We can scarcely suppose, then, that these clouds are raised upon this distant world by the solar heat, especially when we see how feeble that heat is compared with what the earth receives. And this is but another argument to prove the theory of Saturn's present condition as already given, for it is most probable that the planet holds in its own vast bulk the immense amount of heat whose presence is so certainly revealed in these phenomena.

Of course the rings are the unique and most wonderful feature of the whole system. When Galileo first turned his rude telescope upon Saturn, in 1610, he announced that the planet was triple, the projection of the ring on either side making it appear to him as if two smaller planets were joined to the larger one. Gradually, however, these smaller companions decreased in size and finally vanished altogether, much to Galileo's amazement. Later on they reappeared and still further increased his perplexity.

Saturn thus remained an enigma to astronomers until an increase in the power of telescopes brought out the fact that it was surrounded by a thin, flat ring, which, by its varying positions as seen from the earth, caused the peculiar appearances that so puzzled Galileo.

This so-called ring, when seen through large telescopes, appears as a very thin, flat disk with a circular opening in the center in which the planet itself is situated. It lies exactly in the plane of Saturn's equator, and extends considerably more than half the planet's diameter on either side of it. The breadth of the ring is just half the planet's diameter, so that there is quite a space left between its inner edge and the surface of the planet.

We speak of it as a ring, but in reality there are many of them. When favorably situated, a dark division can easily be detected which separates it into an "outer" and an "inner" bright ring; while within the last fifty years a third one, inside of the others, was discovered at Cambridge. This innermost of all, known as the "dark" or "crêpe" ring, is a most peculiar object. In appearance it is more like a shadow than anything else, for it seems to be semi-transparent, inasmuch as the outline of the planet can be seen through it where it crosses the planet's disk. It shades away gradually from the inner edge of the inner bright ring, and becomes fainter until it disappears at some nine thousand miles from the planet's surface.

What the nature of these rings may be is still in some degree a mystery. They are not gaseous, and it has been shown that