Chapter II: Preface: To Second Edition

In preparing a second edition, I have taken advantage of a great number of suggestions made by correspondents and reviewers, to whom I offer my sincerest thanks. I have also inserted discussions of the new planet Pluto, the rotation of the galaxy, the apparent expansion of the universe, and other subjects which have become important since the first edition was published, and in general have tried to bring the book up to date.

J. H. JEANS

DORKING
_2 August 1930_

CONTENTS

PAGE
_Introduction_—The Study of Astronomy 1

_Chapter_ I Exploring the Sky 16

II Exploring the Atom 92

III Exploring in Time 150

IV Carving out the Universe 194

V Stars 253

VI Beginnings and Endings 325

_Index_ 355

PLATES

The Discovery of Pluto FRONTISPIECE

PLATE FACING PAGE
I The Milky Way in the neighbourhood
of the Southern Cross 23

II Planetary Nebulae:
1. N.G.C. 2022
2. N.G.C. 6720 (The Ring Nebula)
3. N.G.C. 1501
4. N.G.C. 7662 28

III The Nebula in Cygnus 29

IV The Great Nebula _M_ 31 in Andromeda 30

V The Nebula N.G.C. 891 in Andromeda
seen edge-on 31

VI The “Horse’s Head” in the Great
Nebula in Orion 37

VII The Trifid Nebula _M_ 20 in Sagittarius 44

VIII Stellar Spectra 51

IX The Globular Cluster _M_ 13 in Hercules 63

X The Region of ρ Ophiuchi 65

XI Magnification of part of the outer
regions of the Great Nebula _M_ 31
in Andromeda 70

XII Magnification of the central region of
the Great Nebula _M_ 31 in Andromeda 71

XIII The tracks of α- and β-particles 113

XIV Collisions of α-particles with Atoms 117

XV The Nebula N.G.C. 4594 in Virgo
The Nebula N.G.C. 7217 204

XVI A sequence of Nebular Configurations:
1. N.G.C. 3379
2. N.G.C. 4621
3. N.G.C. 3115
4. N.G.C. 4594 in Virgo
5. N.G.C. 4565 in Berenice’s hair 207

XVII The “Whirlpool” Nebula _M_ 51 in
Canes Venatici 210

XVIII The Nebula _M_ 81 in Ursa Major 211

XIX The Nebula _M_ 101 in Ursa Major 212

XX The Nebula _M_ 33 in Triangulum 213

XXI The Lesser and Greater Magellanic Clouds 214

XXII Two Nebulae (N.G.C. 4395, 4401) suggestive
of Tidal Action 236

XXIII The twin Nebulae N.G.C. 4567-8
The Nebula N.G.C. 7479 237

XXIV Saturn and its System of Rings 250