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

Schoenfeld, 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

Spiral nebulae, 314-316, 337-338

Spring balance, 166

Spring tides, 192

Spy-glass, 108

"Square of the distance," 43-44

Stannyan, Captain, 90

Star, mass of, how determi