href="@public@vhost@g@gutenberg@html@files@59212@59212-h@59212-h-26.htm.html#para_235" tag="{http://www.w3.org/1999/xhtml}a">235,
247; XIII.
288, 289, 290
Tables, solar, III.
59; IV.
85; V. 111; VIII. 153; X.
224, 225, 226; XI. 235,
247; XIII. 290
Tables, Alfonsine, III.
66, 68; V. 94, 96, 99
Tables, Hakemite, III.
60, 62
Tables, Ilkhanic, III. 62
Tables, Prussian, V.
94, 96, 97, 99; VII. 139
Tables, Rudolphine, V. 94; VII.
148, 151; VIII. 156
Tables, Toletan, III.
61, 66
Tables de la Lune (of Damoiseau), XIII. 286
Tabulae Regiomontanae (of Bessel), XIII. 277
Tangent, III. 59
n, 68
n
Tartars, Tartar astronomy, III. 63
Tebbutt’s comet, XIII, 305
Telescope, III. 67; VI.
118-124, 134; VII.
138; VIII.
152-155; IX.
168; X. 207, 213, 218; XII. 251,
252-258, 260, 262,
271; XIII.
274, 300, 301, 306,
310, 317
Theoria Motus (of Gauss), XIII. 276
Theoria Motuum Lunae (of Euler), XI. 233
Théorie de la Lune (of Clairaut), XI. 233
Théorie ... des Probabilités (of Laplace), XI. 238
Théorie ... du Système du Monde (of Pontécoulant), XIII. 286
Theory of the Moon (of Mayer), X. 226
Theory of the Universe (of Wright), XII. 258
Thetis, VIII. 160
Three bodies, problem of, XI.
228,
230-233, 235
Tidal friction, XIII.
287, 292, 293,
320
Tides, VI. 130; VII. 150; IX.
189; XI. 228-230, 235,
248; XIII.
287,
292, 293, 297,
320
Time, measurement of, I. 4, 5, 16.
See also Calendar, Day, Hour, Month, Week, Year
Titan, VIII. 154
Titania, XII. 255
Toletan Tables, III.
61, 66
Torrid zones, II. 35
Total eclipse, II.
43; VII. 145; X. 205; XIII.
301.
See also Eclipses
Transit instrument, X. 218, 225
n
Transit of Mercury, X. 199
Transit of Venus, VIII. 156; X.
202, 205, 224,
227; XIII.
281, 282, 284
Translations, III. 56, 58, 60, 62, 66, 68
Transversals, V. 110
n
Trepidation, III.
58, 62, 68; IV. 84; V. 112
Trigonometry, II. 37
n, 47
n; III. 59
n, 64
n, 68
n; IV. 74
Trivium, III. 65
Tropical year, II. 42
Tuttle’s comet, XIII. 291
Twilight, III. 69
Twinkling of stars, II. 30
Two New Sciences (of Galilei), VI.
133, 134
n; VIII. 152
Tychonic system, V.
105; VI. 127
Umbra (of sun-spots), VI.
124; XII. 268
Uniform acceleration, VI. 133.
See also Acceleration
Uraniborg, V. 101
Uranometria Nova Oxoniensis, XIII. 316
Uranus, XII.
253, 254, 255, 267; XIII. 276, 288, 289,
297
Uranus, rotation of, XIII. 297
Uranus, satellites of, XI. 250
n; XII.
255, 267; XIII. 272,
295
Variable stars.
See Stars, variable
Variation (of the moon), III.
60; V.
111; VII. 145
Variation of elements or parameters, XI. 233
n,
236, 245
Variations, calculus of, XI. 237
n
Vega, III. 64
Venus, I. 14-16; II. 25, 26, 45, 47, 51; III. 68; IV. 75, 81, 86, 87; V. 98, 100, 103; VI. 121, 123; VII. 136 n, 139, 142, 144; VIII.
154; IX. 181, 185; X. 223, 227; XI. 235, 245; XII.
267, 271; XIII. 282,
297.
See also the following headings
Venus, mass of, XI. 235, 248
Venus, phases of, VI.
123, 129
Venus, rotation of, VIII 160; XII. 267; XIII. 297
Venus, transits of.
See Transits of Venus
Vernal equinox, I. 11.
See also Equinoxes
Vernier, III. 69
n
Vertical, II. 33; X. 221; XIII. 285
Vesta, XIII. 294
Victoria, XIII. 281
Virtual velocities, XI. 237
n
Vortices, VIII.
163; IX. 178, 195
Wave, wave-length (of light) XIII. 299, 300, 302
Weather, prediction of, II. 20; VII. 136
Week, I. 16
Weight, VI. 116, 130; IX. 180
Weights and Measures, Commission on, XI. 237, 238
Whetstone of Witte (of Recorde), V. 95
Winter solstice, I. 11.
See also Solstices
Year, I. 3, 4, 16; II. 19-22, 42, 47; III. 66; V. 111
Year, sidereal, II. 42
Year, tropical, II. 42
Zadkiel’s Almanack, I. 18
n
Zenith, II.
33, 35, 36, 46; III, 64; X. 221
Zenith-sector, X. 206
Zodiac, I.
13; X. 224
Zodiac, signs of the, I. 13
Zodiacal constellations, I. 13
Zones of the earth, II.
35, 47
FOOTNOTES:
1 In our climate 2,000 is about the greatest number ever visible at once, even to a keen-sighted person.
2 Owing to the greater brightness of the stars overhead they usually seem a little nearer than those near the horizon, and consequently the visible portion of the celestial sphere appears to be rather less than a half of a complete sphere. This is, however, of no importance, and will for the future be ignored.
3 A right angle is divided into ninety degrees (90°), a degree into sixty minutes (60′), and a minute into sixty seconds (60″).
4 I have made no attempt either here or elsewhere to describe the constellations and their positions, as I believe such verbal descriptions to be almost useless. For a beginner who wishes to become familiar with them the best plan is to get some better informed, friend to point out a few of the more conspicuous ones, in different parts of the sky. Others can then be readily added by means of a star-atlas, or of the star-maps given in many textbooks.
5 The names, in the customary Latin forms, are: Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpio, Sagittarius, Capricornus, Aquarius, and Pisces; they are easily remembered by the doggerel verses:—
The Ram, the Bull, the Heavenly Twins,
And next the Crab, the Lion shines,
The Virgin and the Scales,
The Scorpion, Archer, and He-Goat,
The Man that bears the Watering-pot,
And Fish with glittering tails.
6 This statement leaves out of account small motions nearly or quite invisible to the naked eye, some of which are among the most interesting discoveries of telescopic astronomy; see, for example, chapter X., §§ 207-215.
7 The custom of calling the sun and moon planets has now died out, and the modern usage will be adopted henceforward in this book.
8 It may be noted that our word “day” (and the corresponding word in other languages) is commonly used in two senses, either for the time between sunrise and sunset (day as distinguished from night), or for the whole period of 24 hours or day-and-night. The Greeks, however, used for the latter a special word, νυχθήμερον.
9 Compare the French: Mardi, Mercredi, Jeudi, Vendredi; or better still the Italian: Martedi, Mercoledi, Giovedi, Venerdi.
10 See, for example, Old Moore’s or Zadkiel’s Almanack.
11 We have little definite knowledge of his life. He was born in the earlier part of the 6th century B.C., and died at the end of the same century or beginning of the next.
12 Theophrastus was born about half a century, Plutarch nearly five centuries, later than Plato.
13 Republic, VII. 529, 530.
14 Confused, because the mechanical knowledge of the time was quite unequal to giving any explanation of the way in which these spheres acted on one another.
15 I have introduced here the familiar explanation of the phases of the moon, and the argument based on it for the spherical shape of the
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