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THE MACMILLAN COMPANY NEW YORK · BOSTON · CHICAGO ATLANTA · SAN FRANCISCO

MACMILLAN & CO., Limited LONDON · BOMBAY · CALCUTTA MELBOURNE

THE MACMILLAN CO. OF CANADA, Ltd. TORONTO

Saturn—photographed at the Lowell Observatory by Mr. E. C. Slipher. September, 1909.

THE EVOLUTION OF WORLDS

BY

PERCIVAL LOWELL, A.B., LL.D.

AUTHOR OF “MARS AND ITS CANALS,” “MARS AS THE ABODE OF LIFE,” ETC.

DIRECTOR OF THE OBSERVATORY AT FLAGSTAFF, ARIZONA; NON-RESIDENT PROFESSOR OF ASTRONOMY AT THE MASSACHUSETTS INSTITUTE OF TECHNOLOGY; FELLOW OF THE AMERICAN ACADEMY OF ARTS AND SCIENCES; MEMBRE DE LA SOCIÉTÉ ASTRONOMIQUE DE FRANCE; MEMBER OF THE ASTRONOMICAL AND ASTROPHYSICAL SOCIETY OF AMERICA; MITGLIED DER ASTRONOMISCHE GESELLSCHAFT; MEMBRE DE LA SOCIÉTÉ BELGE D’ASTRONOMIE; HONORARY MEMBER OF THE SOCIEDAD ASTRONOMICA DE MEXICO; JANSSEN MEDALLIST OF THE SOCIÉTÉ ASTRONOMIQUE DE FRANCE, 1904, FOR RESEARCHES ON MARS; MEDALLIST OF THE SOCIEDAD ASTRONOMICA DE MEXICO FOR STUDIES ON MARS, 1908

ILLUSTRATED

New York THE MACMILLAN COMPANY 1909

All rights reserved

Copyright, 1909,

By THE MACMILLAN COMPANY.

Set up and electrotyped. Published December, 1909.

Norwood Press J. S. Cushing Co.—Berwick & Smith Co. Norwood, Mass., U.S.A.

TO THE PRESIDENT OF THE MASSACHUSETTS INSTITUTE OF TECHNOLOGY TO MY COLLEAGUES THERE AND TO ITS STUDENT BODY TO WHOSE INTEREST AND ATTENTION THESE LECTURES ARE INDEBTED THEY ARE APPRECIATIVELY INSCRIBED

“Si je n’étais pas devenu général en chef et l’instrument du sort d’un grand people, j’aurais couru les bureaux et les salons pour me mettre dans la dépendance de qui que ce fût, en qualité de ministre ou d’ambassadeur? Non, non! je me serais jeté dans l’étude des sciences exactes. J’aurais fait mon chemin dans la route des Galilée, des Newton. Et puisque j’ai réussi constamment dans mes grandes entreprises, eh bien, je me serais hautement distingué aussi par des travaux scientifiques. J’aurais laissé le souvenir de belles découvertes. Aucune autre gloire n’aurait pu tenter mon ambition.”

—Napoleon Iᴱᴿ, quoted by Arago.

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.

CONTENTS

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

Index 253

LIST OF ILLUSTRATIONS

PLATES

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

THE EVOLUTION OF WORLDS