The reason that this ring may be observed at so many angles is because it is inclined about 27 degrees to the plane of the planet's orbit and about 28 degrees to the plane of the ecliptic. In the course of the earth's journey and Saturn's journey around the sun, we sometimes look up at this ring and sometimes down upon it, but when the earth lies exactly in the same plane, we look only on the edge which is so thin that it becomes almost invisible. The thickness of the ring is, indeed, scarcely anything at all in comparison to its width for, although the distance from one side to the other of the entire ring is about 172,000 miles, its edge is estimated as only about 62 miles. When the rings are open, the dark shadow of Saturn's planet may be seen against the light of these rings. "While Saturn whirls, his steadfast shade Sleeps on his luminous ring." --_Tennyson._ This shadow proves that the dull, yellowish glow on the planet is reflected sunlight, and that the planet does not shine with its own light, as a star. THE MOONS OF SATURN Besides all the tiny moonlets in the beautiful ring, ten large moons whirl about the planet Saturn. These give Saturn a system with a radius of 8 million miles, which is quite extensive compared to the earth and moon system which has a radius of 240,000 miles. The moons of Saturn range in size from about 200 miles to nearly 300 miles in diameter but being so far away only Titan, the largest, can be seen except in a large telescope. These satellites were given the names of the brothers and sisters of the God of Time and are called Mimas, Enceladus, Tethys, Dione, Rhea, Titan, Hyperion, Japetus, Phœbe and Themis. Titan, the largest satellite, is 771,000 miles distant from the planet. The nearest one is only 117,000 miles away but there are also three others which are closer to the planet than our moon is to us. Phœbe, the most distant one, is almost 8,000,000 miles away and takes nearly 18 months to make a revolution. It appears as a full moon only once in a year and a half--quite a contrast to Mars' little Phobos who goes through his phases one and a half times every night! Phœbe seems to be possessed with a streak of contrariness for she moves in her orbit around Saturn in the opposite direction from all of the other moons. Japetus, the second largest satellite, has the interesting peculiarity of appearing three or four times as bright when on the western side of Saturn as when on the eastern side of it. This is explained by the supposition that one of its sides has a greater reflecting power than the other and, like our moon, always has the same side toward its planet. We would, therefore, see one side of it when east of Saturn and the other side of it when west of it.