Angles, measurement of, 2. Angular diameter, 7. Annular eclipse, 64. Asteroids, 156. Atmosphere of the earth, 49. of the moon, 103. of Jupiter, 139. of Mars, 153. Aurora, 51. Azimuth, 5, 21. Biela's comet, 181. Bode's law, 134, 232. Bredichin's theory of comet tails, 180. Calendar, O. S. and N. S., 61. Capture of comets and meteors, 176. Canals of Mars, 154. Celestial mechanics, 32. Changes upon the moon, 108. Chemical constitution of sun, 116. of stars, 210. Chromosphere, the sun's, 124. Chronology, 59. Classification of stars, 212. Clocks and watches, 74. sidereal clock, 12. Collisions with comets, 183. Colors of stars, 209. Comets, general characteristics, 158-164. development of, 179, 181. groups, 177. orbits, 161. periodic, 176. spectra, 182. tails, 180. Comets and meteors, relation of, 175. Conic sections, 38. Constellations, 184. Corona, the sun's, 123. Craters, lunar, 105. Dark stars, 201. Day, 52, 62. Declination, 21. Development of comet, 179. of moon, 241. of nebulæ, 245. of stars, 242, 244. of sun, 228. of universe, 226. Distribution of stars and nebulæ, 220. Diurnal motion, 10, 15. Doppler principle, 89. Double nebulæ, 215. Double stars, 198. development of, 244. Driving clock, 80. Earth, atmosphere, 48. mass, 45. size and shape, 44. warming of the earth, 47. Eclipses, nature of, 63. annular eclipse, 64. eclipse limits, 68. eclipse maps, 70, 71. number of, in a year, 69. partial eclipse, 64. prediction of, 70, 71. recurrence of, 72. shadow cone, 64, 66. total eclipse, 64. uses of, 73. Eclipses of Jupiter's satellites, 141. Eclipse theory of variable stars, 205. Ecliptic, 26. obliquity of, 25. Ellipse, 33. Epochs for planetary motion, 30. Energy, radiant, 75. condensation of, 76. Epicycle, 32. Equation of time, 53. Equator, 16, 21. Equatorial mounting, 80. Equinoxes, 25. Ether, 75. Evening star, 31. Faculæ, 122. Falling bodies, law of, 35. Finding the stars, 14. Fraunhofer lines, 87. Galaxy, 219. Geography of the sky, 16. Graphical representation, 6. Grating, diffraction, 84. Gravitation, law of, 37. Harvest moon, 93. Heat of the sun, 118, 126. Helmholtz, contraction theory of the sun, 126, 228. Horizon, 4, 21. Hour angle, 21. Hour circle, 21. Hyperbola, 38. Japetus, satellite of Saturn, 145. Jupiter, 136. atmosphere, 139. belts, 137. invisible from fixed stars, 197. orbit of, 29. physical condition, 139. rotation and flattening, 138. satellites, 140. surface markings, 137. Kepler's laws, 33, 111. Latitude, determination of, 18. Leap year, 61. Lenses, 77. Leonid meteor shower, 172. perturbations of, 174. Librations of moon, 98.