NOTE TO THIS EDITION.

I have taken the opportunity in the present edition to revise the work in accordance with the recent progress of astronomy. I am indebted to the Royal Astronomical Society for the permission to reproduce some photographs from their published series, and to Mr. Henry F. Griffiths, for beautiful drawings of Jupiter, from which Plate XI. was prepared.

ROBERT S. BALL.

Cambridge,
1st May, 1900.

CONTENTS.

page
Introduction[1]
chapter
I.The Astronomical Observatory[9]
II.The Sun[29]
III.The Moon[70]
IV.The Solar System[107]
V.The Law of Gravitation[122]
VI.The Planet of Romance[150]
VII.Mercury[155]
VIII.Venus[167]
IX.The Earth[192]
X.Mars[208]
XI.The Minor Planets[229]
XII.Jupiter[245]
XIII.Saturn[268]
XIV.Uranus[298]
XV.Neptune[315]
XVI.Comets[336]
XVII.Shooting Stars[372]
XVIII.The Starry Heavens[409]
XIX.The Distant Suns[425]
XX.Double Stars[434]
XXI.The Distances of the Stars[441]
XXII.Star Clusters and Nebulæ[461]
XXIII.The Physical Nature of the Stars[477]
XXIV.The Precession and Nutation of the Earth's Axis[492]
XXV.The Aberration of Light[503]
XXVI.The Astronomical Significance of Heat[513]
XXVII.The Tides[531]
Appendix[558]

LIST OF PLATES.

PLATE
I.The Planet Saturn[Frontispiece]
II.A Typical Sun-spotTo face page[9]
A.The Sun""[44]
III.Spots and Faculæ on the Sun""[37]
IV.Solar Prominences or Flames""[57]
V.The Solar Corona""[62]
VI.Chart of the Moon's Surface""[81]
B.Portion of the Moon""[88]
VII.The Lunar Crater Triesnecker""[93]
VIII.A Normal Lunar Crater""[97]
IX.The Lunar Crater Plato""[102]
X.The Lunar Crater Tycho""[106]
XI.The Planet Jupiter""[254]
XII.Coggia's Comet""[340]
C.Comet A., 1892, 1 Swift""[358]
XIII.Spectra of the Sun and of three Stars""[47]
D.The Milky Way, near Messier II.""[462]
XIV.The Great Nebula in Orion""[466]
XV.The Great Nebula in Andromeda""[468]
E.Nebulæ in the Pleiades""[472]
F.ω Centauri""[474]
XVI.Nebulæ observed with Lord Rosse's Telescope""[476]
XVII.The Comet of 1882""[357]
XVIII.Schiaparelli's Map of Mars""[221]