Perseus (constellation), 273, 279, 307, 312 Phases of an inferior planet, 149, 160; of the moon, 149, 160, 183-185 Phlegon, Eclipse of, 85-86 Phobos, 223 Phoebe, retrograde motion of, 240, 250, 336 Phosphorescent glow in sky, 323 Phosphorus (Venus), 150 Photographic survey of sky, international, 290-291 Photosphere, 130-131, 134 Piazzi, 23 Pickering, E.C., 302 Pickering, W.H., 199, 205-206, 220-221, 240, 339-341 Pictor, "runaway star" in constellation of, 281-282, 320, 330 Plane of orbit, 36, 150 Planetary nebulæ, 245, 315 _Planetary and Stellar Studies_, 331 Planetesimal hypothesis, 337-338 Planetoids. _See_ Asteroids Planets, classification of, 229; contrasted with comets, 247; in Ptolemaic scheme, 171; relative distances of, from sun, 31-32 Plato (lunar crater), 198 Pleiades, 284, 296-297, 307 Pliny, 169, 260 Plough, 284, 291-296, 302 Plutarch, 86, 89, 169, 181 "Pointers," 292 Polaris. _See_ Pole Star Pole of earth, Precessional movement of, 176-177, 295, 298-299 Pole Star, 33, 163, 177, 292-296, 300-301 Poles, 30, 163-164; of earth, speed of point at, 164 Pollux, 282, 297 Posidonius, 186 Powell, Sir George Baden, 96 Præsepe (the Beehive), 307 Precession of the Equinoxes, 177, 295, 298-299 Pre-telescopic notions, 55 Primaries, 26 _Princess, The_ (Tennyson), 334 Princeton Observatory, 258 Prism, 121 Prismatic colours, 111, 121 Procyon, 284, 290, 297, 303 Prominences, Solar, 72, 93, 131, 139-140, 143; first observation of, with spectroscope, 94, 140, 236 Proper motions of stars, 126, 281-285, 326, 329-330 Ptolemæus (lunar crater), 198-199, 204 Ptolemaic idea, 319; system, 18, 19, 158, 171-172 Ptolemy, 18, 101, 171, 290, 296 Puiseux, P., 206 Pulkowa telescope, 117 Puppis, V., 310 Quiescent prominences, 139 Radcliffe Observer, 139 "Radiant," or radiant point, 269 Radiation from sun, 130, 134 Radium, 129, 138 Rainbow, 121 "Rainbows, Bay of," 197 Rambaut, A., 139 Ramsay, Sir William, 138 Rays (on moon), 204 Recurrence of eclipses, 74-80 Red (rays of light), 121, 125, 127, 130 Red Spot, the Great, 230 Reflecting telescope, 111-116; future of, 119 Reflector. _See_ Reflecting telescope Refracting and reflecting telescopes contrasted, 118 Refracting telescope, 109-111, 115-117; limits to size of, 119-120 Refraction, 121, 168-169 Refractor, _See_ Refracting telescope Regulus, 290, 296 Retrograde motion of Phoebe, 240, 250, 336 "Reversing Layer," 94, 130, 132, 137-138 Revival of learning, 107 Revolution, 30; of earth around sun, 170-173; periods of sun and planets, 35 Riccioli, 198 Rice-grain structure of photosphere, 134 Rigel, 285, 297 Rills (on moon), 204 Ring-mountains of moon. _See_ Craters "Ring" nebulæ, 315, 337 "Ring with wings," 87