388

THE PLANET SATURN.

we have shown, in Fig . LXXXVIII., that it is impossible tosee the rings from any place situated at more than a certaindistance north or south of the planet’s equator; so it may becalculated that, in order to see Mimas, the nearest satellite, itwould be necessary to descend about 17^° from either pole ;and 13J°, and 10^°, respectively, in order to see Enceladus andTethys.

The satellites would, of course, go through their variousphases in a manner similar to our Moon , only much more rapidly.When in the phase of Full Moon they would also, at times,,pass through the shadow of the planet, and he eclipsed. Indeed,for a considerable period on each side of an equinox an eclipseof a full moon would he the rule, except in the case of Iapetus,which, owing to its greater distance from Saturn , would almostalways escape. But the eclipses would not continue to be sofrequent during the whole of Saturn ’s year as in the case ofJupiter’s satellites, because the equator of Saturn , and the orbitsof its moons, are so much more inclined to the plane of its path.As a solstice approaches it will be remembered that we havealready stated, that the outer portion of the rings escapes theshadow of the planet, owing to the tilt of their path. Con-sequently the satellites, whose orbits are equally tilted, so thatthey would appear, as seen from the Sun, to describe curvessimilar to the outer boundary of the rings, only farther awayfrom Saturn , would still more easily escape the shadow; theouter almost invariably,. the innermost for about two yearsboth before and after, as well as during, the time in which theshadow falls short of the more distant portion of the ring.

We have explained (see Lecture IV., p. 91) that the Earth ’sMoon really looks ^th wider in diameter when seen in thezenith than when seen in the horizon ; and we have shownthat a similar, but more striking, effect of the same kind takesplace in the case of those of Mars (see Lecture X., p. 257).Those of Saturn , owing to their proximity to the planet, wouldbe so especially near to an observer when seen close to thezenith, that the alteration of their apparent size would be veryimportant. The nearest, for instance, would look about twiceas large in area, while even the third would appear half as