;
texture of, 34;
tides on, 530;
velocity of, 484;
weight of, compared with Jupiter, 250, 350;
zodiacal light and, 67;
zones on the surface of, 39

Sunbeam, revelations of a, 44

Swan, the, 424, 439, 445

Sword-handle of Perseus, 462

Syrtis major, 222

T

Taurus, constellation of, 231, 419

Tebbutt's comet, 353

Telescope, construction of the first, 10;
equatorial (Dunsink), 12-14, 185;
Greenwich, 26;
Herschelian, 19;
Lick, 16, 19;
Paris, 22, 23;
reflecting, 19, 21;
refracting, 11, 14;
Rosse, 19, 20, 468, 470;
sighting of a, 23;
structure of the eye illustrates the principle of the, 10;
Vienna, 14-16;
Washington, 226;
Yerkes, 16

Temporary stars, 430, 488

Tethys, 559

Theophilus, 92

Tides, The, actual energy derived from the Earth, 539;
affected by the law of gravitation, 149, 535;
affected by the Moon, 70, 535-537;
at Bay of Fundy, 538;
at Cardiff, 538;
at Chepstow, 538;
at London, 538;
at St. Helena, 538;
excited by the Sun, 537;
formation of currents, 538;
in Bristol Channel, 538;
in Mediterranean, 537;
in mid-ocean, 538;
Jupiter and, 552;
length of the day and, 541;
lunar, 548, 549;
moment of momentum and, 552;
neap, 537;
rotation of the Earth, and revolution of the Moon, 549;
satellites of Mars, 551;
solar, 550;
spring, 537;
variations in, 538;
waste of water power, 538;
work effected, 539

Tin in the Sun, 50

Titan, 294, 295, 559

Titania, 309, 559

Transit of Mercury, 152, 163, 164

Transit of Venus, 152;
Captain Cook, 184;
Copeland's observations of, 189;
Crabtree's observations of, 180;
Gassendi's observations of, 178;
Halley's method, 180, 181;
Horrocks' observations of, 179, 180;
importance of, 173;
Kepler's prediction of, 163;
observations of, at Dunsink, 184-188

Transit of Vulcan, 152-153

Triesnecker, 84, 93

Trouvelot, Mr. L., and Saturn's rings, 278

Tschermak, and the origin of meteorites, 400, 401

Tycho (lunar crater), 91

Tycho Brahe, and the Observatory of Uraniborg, 9, 10, 430

U

Umbra of Sun-spot, 51

Umbriel, 309, 559

Unstable dynamical equilibrium, 543

Uraniborg, Observatory of, 10

Uranus, 112;
attraction of Saturn, 322;
Bradley's observations of, 312;
composition of, 308;
density of, 558;
diameter of, 308, 558;
diameter of orbit of, 305;
disc of, 308;
discovery of, by Herschel, 305, 30