Name. Discoverer. Mean Sidereal Diameter. Apparent Apparent distance period. Miles. diameter star from d. h. m. of Saturn magnitude. Saturn. seen from Miles. satellite. ° 1. MIMAS Sir W. Herschel, 115,000 0 22 37 1,000 33 17 Sept, 17, 1789 2. ENCELADUS ″ ″ Aug. 28, 1789 147,000 1 8 53 ? 26 15 3. TETHYS J. D. Cassini, 183,000 1 21 18 500 21 13 March, 1684 4. DIONE ″ ″ March, 1684 234,000 2 17 41 500 16 12 5. RHEA ″ ″ Dec. 23, 1672 327,000 4 12 25 1,200 12 10 6. TITAN Huygens, Mar. 25, 758,000 15 22 41 3,300 5 8 1653 7. HYPERION W. Bond & 916,000 21 7 7 ? 4 17 Lassell, Sept, 19, 1848 8. IAPETUS J. D. Cassini, 2,221,000 79 7 53 1,800 2 9 Oct. 25, 1671 SATELLITES OF URANUS. Name. Discoverer. Mean distance Sidereal Maximum from Uranus. period. elongation. Miles. d. h. m. ″ 1. ARIEL Lassell, September 124,000 2 12 28 12 14, 1847 2. UMBRIEL O. Struve, October 8, 173,000 4 3 27 15 1847 3. TITANIA Sir W. Herschel, 285,000 8 16 55 33 January 11, 1787 4. OBERON ″ ″ 381,000 13 11 6 44 SATELLITE OF NEPTUNE. Discoverer. Mean distance Sidereal Maximum Apparent from Neptune. period. elongation. star Miles. d. h. m. ″ magnitude. Lassell, October 223,000 5 21 8 18 14 10, 1846 GENERAL INDEX. A. Adams, J. C., 145. Airy, Sir G. B., 145. Anagram on Venus, 68; on Saturn, 127. Aphelion, 11, 102. Apparent movements of the Planets, 12, 14. Arago, D. J. F., 99, 124, 140. Arctic regions of the Earth, 75. Argelander, F. G. A., 178. Aristarchus of Samos, 71. Aristarchus (Lunar Mountain), 93, 94. Asteroids, 110. Aurora Borealis and spots on the Sun, 55; and twinkling, 87. Autumnal Equinox, 74. Axial rotation of the Planets, 17, 183.