TO THE
REVISED EDITION.
Since the first publication of these Letters, in 1840, the work has passed through numerous editions, and received many tokens of public favor, both as a class-book for schools and as a reading-book for the family circle. The valuable discoveries made in the science within a few years have suggested an additional Letter, which is accordingly annexed to the series in the present revised form, giving a brief but comprehensive notice of all the leading contributions with which Astronomy has of late been enriched.
The form of Letters was chosen on account of the greater freedom it admits, both of matter and of style, than a dress more purely scientific. Thus the technical portion of the work, it was hoped, might be relieved, and the whole rendered attractive to the youthful reader of either sex by interspersing sketches of the master-builders who, in successive ages, have reared the great temple of Astronomy, composing, as they do, some of the most remarkable and interesting specimens of the human race.
The work was addressed to a female friend (now no more), who was a distinguished ornament of her sex, and whose superior intellect and refined taste required that the work should be free from every thing superficial in matter or negligent in style; and it was deemed by the writer no ordinary privilege that, in the composition of the work, an image at once so exalted and so pure was continually present to his mental vision.
CONTENTS.
| Preface, | 3 | |
| [LETTER I]. | ||
|---|---|---|
| Introductory Observations, | 9 | |
| [LETTER II.] | ||
| Doctrine of the Sphere, | 16 | |
| [LETTER III.] | ||
| Astronomical Instruments.—Telescope, | 29 | |
| [LETTER IV] | ||
| Telescope continued, | 36 | |
| [LETTER V.] | ||
| Observatories, | 42 | |
| [LETTER VI.] | ||
| Time and the Calendar, | 59 | |
| [LETTER VII.] | ||
| Figure of the Earth, | 69 | |
| [LETTER VIII.] | ||
| Diurnal Revolution, | 81 | |
| [LETTER IX.] | ||
| Parallax and Refraction, | 89 | |
| [LETTER X.] | ||
| The Sun, | 101 | |
| [LETTER XI.] | ||
| Annual Revolution.—Seasons, | 111 | |
| [LETTER XII.] | ||
| Laws of Motion, | 126 | |
| [LETTER XIII.] | ||
| Terrestrial Gravity, | 134 | |
| [LETTER XIV.] | ||
| Sir Isaac Newton.—Universal Gravitation.—Figure | ||
| of the Earth's Orbit.—Precession of the Equinoxes, | 143 | |
| [LETTER XV.] | ||
| The Moon, | 157 | |
| [LETTER XVI.] | ||
| The Moon.—Phases.—Harvest Moon.—Librations, | 172 | |
| [LETTER XVII.] | ||
| Moon's Orbit.—Her Irregularities, | 180 | |
| [LETTER XVIII.] | ||
| Eclipses, | 195 | |
| [LETTER XIX.] | ||
| Longitude.—Tides, | 208 | |
| [LETTER XX.] | ||
| Planets.—Mercury and Venus, | 225 | |
| [LETTER XXI.] | ||
| Superior Planets: Mars, Jupiter, Saturn, and Uranus, | 243 | |
| [LETTER XXII.] | ||
| Copernicus.—Galileo, | 254 | |
| [LETTER XXIII.] | ||
| Saturn.—Uranus.—Asteroids, | 274 | |
| [LETTER XXIV.] | ||
| The Planetary Motions.—Kepler's Laws.—Kepler, | 291 | |
| [LETTER XXV.] | ||
| Comets, | 312 | |
| [LETTER XXVI.] | ||
| Comets, | 334 | |
| [LETTER XXVII.] | ||
| Meteoric Showers, | 346 | |
| [LETTER XXVIII.] | ||
| Fixed Stars, | 365 | |
| [LETTER XXIX.] | ||
| Fixed Stars, | 383 | |
| [LETTER XXX.] | ||
| System of the World, | 392 | |
| [LETTER XXXI.] | ||
| Natural Theology, | 406 | |
| [LETTER XXXII.] | ||
| Recent Discoveries, | 414 | |
| [INDEX.] | 423 |