Rings of Saturn, 108, 236-239, 241-243, 334 Ritchey, G.W., 118 Roberts, A.W., 308, 310 Roberts, Isaac, 325 "Roche's limit," 238 Roemer, 235 Roman history, eclipses in, 85-86 Romulus, 85 Röntgen, 120 Rosse, great telescope of Lord, 117, 314 Rotation, 30; of earth, 33, 161-165, 170; of sun, 34, 125, 135-136, 231; periods of sun and planets, 35 Royal Society of London, 90-91, 111 Rubicon, Passage of the, 85 "Runaway" stars, 281, 326, 330 Sagittarius (constellation), 316 Salt, spectrum of table, 122 Samarcand, 107 "Saros," Chaldean, 76-78, 84 Satellites, 26-27, 37 Saturn, 20, 22, 34, 37, 108, 236-243, 258; comet family of, 252; a puzzle to the early telescope observers, 241-243; retrograde motion of satellite Phoebe, 240, 250, 336; ring system of, 241; satellites of, 36, 239-240; shadows of planet on rings and of rings on planet, 237 Schaeberle, 95-96, 303, 316 Schiaparelli, 155, 214, 223 Schickhard (lunar crater), 199 Schmidt, 206 Schönfeld, 290 Schuster, 95 Schwabe, 136 Scotland, solar eclipses visible in, 89-90, 92 Sea of Serenity, 205 "Sea of Showers," 197 "Seas" of moon, 197, 206 Seasons on earth, 174-175; on Mars, 211 Secondary bodies, 26 Seneca, 95, 260 _Septentriones_, 291 Serenitatis, Mare, 205 "Seven Stars," 291 "Shadow Bands," 69 Shadow of earth, circular shape of, 62-64 Shadows on moon, inky blackness of, 202 Shakespeare, 259, 293 Sheepshanks Telescope, 119 "Shining fluid" of Sir W. Herschel, 328 "Shooting Stars." _See_ Meteors Short (of Edinburgh), 114 "Showers, Sea of," 197 Sickle of Leo, 270-271, 296 Siderostat, 118 Silver, 145 Silvered mirrors for reflecting telescopes, 116 Sinus Iridum, 197 Sirius, 280, 282, 284-285, 288-290, 297, 303-304, 320; companion of, 303; stellar magnitude of, 289 Size of celestial bodies, how ascertained, 59 Skeleton telescopes, 110 Sky, international photographic survey of, 290-291; light of the, 323 Slipher, E.C., 213, 222 Smithsonian Institution of Washington, 98 Snow on Mars, 213 Sodium, 122, 124, 254 Sohag, 95 Solar system, 20-21, 29-31; centre of gravity of, 42; decay and death of, 344 Somniorum, Lacus, 197 Sound, 125, 166, 331 South pole of heavens, 163, 285, 298-299 Southern constellations, 298-299 Southern Cross. _See_ Crux Space, 328 Spain, early astronomy in, 107; eclipse tracks across 93, 97-98 Spectroheliograph, 140 Spectroscope, 120, 122, 124-125, 144-145, 212, 231; prominences first observed with, 94, 140, 236 Spectrum of chromosphere, 132-133; of corona, 133; of photosphere, 132; of reversing layer, 132, 137; solar, 122-123, 127, 132 Speculum, 111, 116; metal, 112 Spherical bodies, 29 Spherical shape of earth, proofs of, 158-161 Spherical shapes of sun, planets, and satellites, 160