The cuts with which the book is illustrated have been drawn from all available sources; and it is believed that they excel in number, freshness, beauty, and accuracy those to be found in any similar work. The lithographic plates are, with a single exception, reductions of the plates prepared at the Observatory at Cambridge, Mass. The remaining lithographic plate is a reduced copy of Professor Langley's celebrated sun-spot engraving. Many of the views of the moon are from drawings made from the photographs in Carpenter and Nasmyth's work on the moon. The majority of the cuts illustrating the solar system are copied from the French edition of Guillemin's "Heavens." Most of the remainder are from Lockyer's "Solar Physics," Young's "Sun," and other recent authorities. The cuts illustrating comets, meteors, and nebulæ, are nearly all taken from the French editions of Guillemin's "Comets" and Guillemin's "Heavens." CONTENTS. I. THE CELESTIAL SPHERE 3 II. THE SOLAR SYSTEM 41 I. THEORY OF THE SOLAR SYSTEM 41 The Ptolemaic System 41 The Copernican System 44 Tycho Brahe's System 44 Kepler's System 44 The Newtonian System 48 II. THE SUN AND PLANETS 53 I. The Earth 53 Form and Size 53 Day and Night 57 The Seasons 64 Tides 68 The Day and Time 74 The Year 78 Weight of the Earth and Precession 83 II. The Moon 86 Distance, Size, and Motions 86 The Atmosphere of the Moon 109 The Surface of the Moon 114 III. Inferior and Superior Planets 130 Inferior Planets 130 Superior Planets 134 IV. The Sun 140 I. Magnitude and Distance of the Sun 140 II. Physical and Chemical Condition of the Sun 149 Physical Condition of the Sun 149 The Spectroscope 152 Spectra 158 Chemical Constitution of the Sun 164 Motion at the Surface of the Sun 168 III. The Photosphere and Sun-Spots 175 The Photosphere 175 Sun-Spots 179 IV. The Chromosphere and Prominences 196 V. The Corona 204 V. Eclipses 210 VI. The Three Groups of Planets 221 I. General Characteristics of the Groups 221 II. The Inner Group of Planets 225 Mercury 225 Venus 230 Mars 235 III. The Asteroids 241 IV. Outer Group of Planets 244 Jupiter 244 The Satellites of Jupiter 250 Saturn 255 The Planet and his Moons 255 The Rings of Saturn 261 Uranus 269 Neptune 271 VII. Comets and Meteors 274 I. Comets 274 General Phenomena of Comets 274 Motion and Origin of Comets 281 Remarkable Comets 290