The substance of the following pages was written and presented in a university course of lectures before the Massachusetts Institute of Technology—in February and March of this year. The kind interest with which the lectures were received, not only by the students and professional bodies, but by the public, was followed by an immediate request from The Macmillan Company to issue them in book form, and as such they now appear.
PERCIVAL LOWELL. BOSTON, MASS., May 29, 1909.
CHAPTER PAGE I. BIRTH OF A SOLAR SYSTEM 1 II. EVIDENCE OF THE INITIAL CATASTROPHE IN OUR OWN CASE 31 III. THE INNER PLANETS 58 IV. THE OUTER PLANETS 94 V. FORMATION OF PLANETS 127 VI. A PLANET’S HISTORY—SELF-SUSTAINED STAGE 155 VII. A PLANET’S HISTORY—SUN-SUSTAINED STAGE 182 VIII. DEATH OF A WORLD 213
NOTES 1. METEOR ORBITS 241 2. DENSITIES OF THE PLANETS 243 3. VARIATION IN SPECTROSCOPIC SHIFT 243 4. ON THE PLANETS’ ORBITAL TILTS 244 5. PLANETS AND THEIR SATELLITE SYSTEMS 245 6. ON THE INDUCED CIRCULARITY OF ORBITS THROUGH COLLISION 250 7. CAPTURE OF SATELLITES 251
I. Saturn _Frontispiece_ OPPOSITE PAGE II. The Moving Nebula surrounding Nova Persei, 1901-1902 14 III. Representative Stellar Spectra 24 IV. Spectra of the Major Planets 52 V. Venus, 1896-1897 82 VI. Asteroids: Major Axes of Orbits 98 VII. Saturn—A Drawing showing Agglomerations 108 VIII. Spectrogram of Jupiter, Moon Comparison 152 IX. Spectrogram showing Water-vapor in Atmosphere of Mars 160 X. Tree Fern 176 XI. Ten Views of Mercury, showing Effect of Libration 222 XII. Spectrogram of Saturn 232
CUTS APPEARING IN TEXT PAGE Algol and its Dark Companion 4 Nova Persei 11 Spectrum of Nova Persei 12 The Moving Nebula surrounding Nova Persei, 1901 13 Great Nebula in Orion 17 Great Nebula in Andromeda 18 Nebula M. 100 Comæ 19 Nebula ♅ I. 226 Ursæ Majoris 20 Nebula ♅ V. 24 Comæ. Showing Globular Structure 21 Nebula M. 101 Ursæ Majoris 23 The Radiant of a Meteoric Shower 37 Diagram explaining Proportionate Visibility of Meteors 38 The Mart Iron 41 Section of Meteorite showing Widmannstättian Lines 42 Meteorite, Toluca 43 Nebula ♅ V. 14 Cygni 45 Nebula N.G.C. 1499 Persei 46 Nebula N.G.C. 6960 in Cygnus 47 Nebula M. 51 Canum Venaticorum 48 Orbits of the Inner Planets 59 Sulla Rotazione di Mercurio.—Di G. V. Schiaparelli 64 Map of Mercury. Lowell 69 Venus. October, 1896-March, 1897 78 Venus. April 12, 1909. 79 Diagram: Convection Currents in Atmosphere of Venus 81 Diagram: Shift in Central Barometric Depression 81 Spectrogram of Venus, showing its Long Day 87 Spectrogram of Jupiter, giving the Length of its Day by the Tilt of its Spectral Lines 89 Orbits of the Outer Planets 95 Drawing of Jupiter showing its Ellipticity 103 Two Drawings of Jupiter and its Wisps 105 Photograph of Jupiter, 1909 107 Diagram of Saturn’s Rings 113 The Tores of Saturn 114 Chart showing increasing Tilts of the Major Planets 131 Orbital Tilts and Eccentricities of Satellites 133 Masses of Planets and Satellites 136 Two Drawings of Jupiter and its “Great Red Spot” 164 Sun Spots 165 Photograph of a Sun Spot 166 The Volcano Colima, Mexico, March 24, 1903 169 Jukes Butte, a Denuded Laccolith, as seen from the Northwest 170 Ideal Section of a Laccolith 170 Earth as seen from above.—Photographed at an Altitude of 5500 Feet 183 Tracks of Sauropus Primævus 188 Adventures of a Heat Ray 193 Polar Caps of Mars at their Maxima and Minima 198 Glacial Map of Eurasia 200 Map showing the Glaciated Area of North America 201 Photograph of the Moon 205 Petrified Bridge, Third Petrified Forest, near Adamana, Arizona 210 Three Views of Venus, showing Agreement at Different Distances 220 Diagram of Libration in Longitude due to Rotation 222 Moon,—Full and Half 225 Diagram illustrating Molecular Motion in a Gas 227 Distribution of Molecular Velocities in a Gas 229