| Preface, | | 3 |
| [LETTER I]. |
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| Introductory Observations, | | 9 |
| [LETTER II.] |
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| Doctrine of the Sphere, | | 16 |
| [LETTER III.] |
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| Astronomical Instruments.—Telescope, | | 29 |
| [LETTER IV] |
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| Telescope continued, | | 36 |
| [LETTER V.] |
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| Observatories, | | 42 |
| [LETTER VI.] |
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| Time and the Calendar, | | 59 |
| [LETTER VII.] |
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| Figure of the Earth, | | 69 |
| [LETTER VIII.] |
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| Diurnal Revolution, | | 81 |
| [LETTER IX.] |
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| Parallax and Refraction, | | 89 |
| [LETTER X.] |
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| The Sun, | | 101 |
| [LETTER XI.] |
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| Annual Revolution.—Seasons, | | 111 |
| [LETTER XII.] |
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| Laws of Motion, | | 126 |
| [LETTER XIII.] |
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| Terrestrial Gravity, | | 134 |
| [LETTER XIV.] |
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| Sir Isaac Newton.—Universal Gravitation.—Figure |
| of the Earth's Orbit.—Precession of the Equinoxes, | | 143 |
| [LETTER XV.] |
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| The Moon, | | 157 |
| [LETTER XVI.] |
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| The Moon.—Phases.—Harvest Moon.—Librations, | | 172 |
| [LETTER XVII.] |
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| Moon's Orbit.—Her Irregularities, | | 180 |
| [LETTER XVIII.] |
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| Eclipses, | | 195 |
| [LETTER XIX.] |
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| Longitude.—Tides, | | 208 |
| [LETTER XX.] |
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| Planets.—Mercury and Venus, | | 225 |
| [LETTER XXI.] |
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| Superior Planets: Mars, Jupiter, Saturn, and Uranus, | | 243 |
| [LETTER XXII.] |
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| Copernicus.—Galileo, | | 254 |
| [LETTER XXIII.] |
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| Saturn.—Uranus.—Asteroids, | | 274 |
| [LETTER XXIV.] |
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| The Planetary Motions.—Kepler's Laws.—Kepler, | | 291 |
| [LETTER XXV.] |
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| Comets, | | 312 |
| [LETTER XXVI.] |
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| Comets, | | 334 |
| [LETTER XXVII.] |
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| Meteoric Showers, | | 346 |
| [LETTER XXVIII.] |
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| Fixed Stars, | | 365 |
| [LETTER XXIX.] |
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| Fixed Stars, | | 383 |
| [LETTER XXX.] |
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| System of the World, | | 392 |
| [LETTER XXXI.] |
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| Natural Theology, | | 406 |
| [LETTER XXXII.] |
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| Recent Discoveries, | | 414 |
| [INDEX.] | | 423 |
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