SATURN (PLANETS, ante). The mean distance of Saturn from the Sun is 872,137,000 m., but the greatest and least distances differ nearly 49,000,000 m., being 1)20,973,000 and 823,301,000 miles. The eccentricity of his orbit is 1.055996, and he completes a circuit around the sun in a periotl'of 29 years 167.2 days. While the volume of Saturn is 700 times that of the earth his mass is only about 90 times as much; his density being less than that of any other planet or planetoid. Taking the earth's density as unity,‘ Saturn's is 0.13. Compared to the density of water, t•at of Saturn is as 73 to 100. His mean diameter is about 70,000 m., with a polar compression of about so that the polar diameter is about 63,500, and the equatorial about 73.50) miles. The rings of Saturn are his most remarkable characteristics. The breadth of the system of rings from the outside of the larger to the'inside of the smaller is about 29,900 in., and the diam eter of the outer ring is 167,000 miles. Three rings are usually counted, as with ordinary telescopic power they present that appearance, but increased power together with cal culations made upon the effects of light make it probable that each of these three rings is subdivided into numerous others Inside of the system of bright rings, there n; a dark ring having a breadth of 87,000 miles, or more than the diameter of the earth. It wits discovered bythe elder Bond of Harvard university. This is also probably a multiple ring, and, the inner diameter is about 90,000 m., leaving a space of about 10.000 m. between the innermost dark ring and the surface of the planet. In regard to the sub
division of the rings, recent investigations have made it probable that they are composed of numerous small satellites mingled with vaporous matter traveling in planes. The bright rings of Saturn were discovered by the Dutch astronomer Huygens in 1659. He had already discovered one of the satellites with in telescope of his own construction, having a focal length of 10 feet.. The instrument with which he discovered the ring had a focal length of 22 feet, and was much the largest telescope ever constructed up to that time. The appearance of two luminous bodies on either side of the planet at various times had been observed by Galileo, but his telescope did not permit him to make nut what the phenomena were. Huygens ascertained that the luminous appearances were caused by the reflection of the sun oa two parts of the rings. From a calculation made from the position of the rings and the planet's revolution, he predicted the return of the lumin ous appearances in 1671, a prediction which was verified. The late prof. Peirce of Harvard canoe to the conclusion that the major planets must be still in a state of intense heat. Sir W. Herschel, Bond, Airy, and others also observed that changes of figure took place, consisting of bulgings out of regions corresponding to our temperate zones, with depressions at the poles and equator, or elevation of one polar region with depres sion of the other.. This is accounted for by supposing the existence of great and dense cloud masses in the atmosphere of the planet.