Besides its system of rings, which makes Saturn the most remarkable planet of the solar system, this globe is attended by eight satellites, moving in orbits whose planes very nearly coincide with the plane of the rings, except that of the most distant one, which has an inclination of about 12° 14'. In the order of their distance from the planets, the satellites of Saturn are as follows: Mimas, Enceladus, Tethys, Dione, Rhea, Titan, Hyperion and Iapetus. The three first satellites are nearer to Saturn than the Moon is to the Earth; while Iapetus, the farthest, is 9½ times the distance of our satellite from us. All the satellites, with the exception of the farthest, move more rapidly around Saturn than the Moon moves around the Earth; while Iapetus, on the contrary, takes almost three times as long to make one revolution. The period of revolution of the four inner satellites is accomplished in less than three days, that of Mimas being only a little more than 22 hours. From such swiftness of motion, it is easily understood how short must be the intervals between the different phases of these satellites. Mimas, for instance, passes from New Moon to First Quarter in less than 6 hours. The distance of the nearest satellite from the planet's surface is 84,000 miles, and its distance from the outer ring only 36,000 miles. It is difficult to determine the diameter of objects so faint and distant as are some of these satellites, but the diameter of Titan, the largest of all, is pretty well known, and estimated to be ¹⁄₁₆ the diameter of the planet, or more than half the diameter of our globe. Iapetus is subject to considerable variations in brilliancy, and as the maxima and minima always occur when this satellite occupies the same parts of its orbit, it was conjectured by W. Herschel that, like our Moon, it turns once upon its axis during each of its revolutions about the planet. It has been shown by my observations, that Iapetus attains its maximum brightness a little before it reaches its greatest western elongation, and its minimum on the opposite side. As the planes of the orbits of the satellites are inclined to the planet's orbit, it follows that their transits, occultations and eclipses, are only possible when Saturn is near its equinoxes. Passages of the satellites and their shadows across the disk, although rare, have been observed, and they somewhat resemble the phenomena exhibited by the satellites of Jupiter in transit. When the Earth is very near the plane of the rings, the satellites, except the farthest, appear to be in a straight line nearly coincident with the plane of the rings, and are seen occasionally moving along the thin edge of the rings, appearing as luminous beads moving on a thread of light.