Saturn, age of, 189. composition of, 190. density of, 188. distance of, 186. the gauze ring, 199-202. gravity on, 188. inclination of axis, 187. interior of, 206. length of year, 186. popular telescopic object, 185. rings of, 185, 196. gaps in, 197. origin of, 200. periodic disappearance of, 198. seen from planet, 207. shadow of, 198. rotation of, 187. satellites of, 195. size of, 187. Schiaparelli discovers canals on Mars, 90. describes Martian canals, 93. discovers Mercury's rotation, 30, 32. on rotation of Venus, 76. Solar system, shape and size of, 14. unity of, 9. viewed from space, 11. Stoney, Johnstone, on atmospheres of planets, 116. on escape of gases from moon, 231. Sun, the, isolation in space, 13. no life on, 10. resemblances with Jupiter, 174. Swedenborg, on Saturn's rings, 204. Tidal friction, 80, 81, 236, 253. Tycho, lunar crater, 222. Ultra-Neptunian planet, 210. Uranus, description of, 208-210. Venus, age of, 58. atmosphere of, 53, 55, 59, 61, 68. absence of seasons on, 51. density of, 47. distance of, 47, 50. gravity on, 46, 47. inclination of axis, 50. life on, 57, 58, 61, 65, 67, 68, 82, 117. light and heat on, 50-57. orbit of, 50. phases of, 49. resemblances of, to earth, 46. rotation of, 76, 79, 80. size of, 46. twilight on, 83. visibility of, 47. Vesta, an asteroid, 129, 130, 138. Vogel on Mercury's atmosphere, 21. Wireless telegraphy, 1, 112. Young, C.A., on Olbers's theory of asteroids, 142. on temperature of Mars, 122. on Venus's atmosphere, 53. Zodiac, the, 258. THE END A NEW BOOK BY PROF. GROOS. The Play of Man. By KARL GROOS, Professor of Philosophy in the University of Basel, and author of "The Play of Animals." Translated, with the author's cooperation, by Elizabeth L. Baldwin, and edited, with a Preface and Appendix, by Prof. J. Mark Baldwin, of Princeton University. 12mo. Cloth, $1.50 net; postage, 12 cents additional.