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, 191-192 Algol, the problem of, 179-184 dimensions and constitution of, 187-188, 190 Alpha Centauri, nearest star to the sun, 208 earth viewed from, 330 America, tropical, effects of eclipse in, 80-81 astronomy in, 105-106 Animals, extinct, eyes of, 17 duration of life on earth, 253-256, 272-275 Area of the sky in degrees, 238 Asteroids, airless, 132 waterless, 134 Astronomy in America, 105-106 now and thirty years ago, 148-150 and photography, 158 the doctrine of probability, 230, 241, 245 Aurora Borealis, conjectures as to cause, 163 Prof. Johnston and the "green line," 163

, Prof. E. E., photograph of the celestial pole, 53 discovery of the fifth satellite of Jupiter, 105

, the spiral nebula in, 35, 37 Carboniferous epoch, aspect of the heavens in, 16 Castor, 201 Centauri Alpha, star nearest the sun, 208 earth viewed from, 330 Chandler, Mr., and the movements of the terrestrial pole, 67-68, 73 Colours and vibrations, 175 Coal, 257 Comets in the epoch of the coal measures, 19 connection with meteors, 167 their electric character, 168 and the law of gravitation, 199 and the Nebular Hypothesis, 222-224 nature of, 302-303 amount of refractive matter in, 304-305 weight of, 306 Holmes' comet, Swift's, 53 Lexell's comet in collision with Jupiter, 306 Comte's view of astronomy falsified, 149 Coon Butte "irons," proof of terrestrial origin of meteorites, 351-352 Critical velocities, 133