The Evolution of Worlds

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

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

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