PREFACE

IN class-books of astronomy and geography, facts relating to the earth's movements and place in the universe are usually treated in an inadequate manner. Students are informed that the earth is a globe; that it rotates on an axis; revolves round the sun, and is one of a family of planets; but they are not taught these matters scientifically. The scientific method of observation and induction should be used in elementary astronomy as in other physical sciences. Celestial phenomena must be observed before the theories that explain them can be properly understood. This has been borne in mind in the design of the following pages. The first chapter deals with star-groups and the apparent diurnal motion of the celestial sphere.

In the second chapter it is

shown that all the phenomena previously described can be explained by the fact that the earth is a globe in rotation. The determination of the size

and mass of the earth is the subject of Chapter III. Then comes an account of the apparent annual motion of the sun among the stars, and the apparent motions of planets. And, finally, it is shown in Chapter V. that these appearances are easily explainable on the Copernican theory of the order of the universe.

For ages the whole of astronomy was concerned with the movements and varying dispositions of the heavenly bodies. It is hoped that this little book will help to revive the observational astronomy of pre-telescopic times. There is pleasure to be found in the mere contemplation of the heavens, and a knowledge of the causes of the varying appearances presented brings with it the keenest satisfaction.

Most of the illustrations have been specially drawn for the book, from my sketches, by Mr. W. H. Harvey, B.A. A few are from M. Flammarion's Astronomical Myths, and for permission to use these I am indebted to the publishers.

Commissary-General G. D. Lardner has kindly assisted me by reading the proof-sheets of the book, and by calling my attention to several points which had escaped my notice.

R. A. GREGORY.

WIMBLEDON, SURREY,

October 1894.

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CHAPTER I

THE HEAVENS WE SEI

Number of stars-Star-groups or constellation

The Plough or Ursa Major-The Pole-Sta
Taurus The Pleiades-Canis Major-Cani
-Virgo-Bootes-Corona Borealis - He

-- Aquila-Pegasus-Andromedae-Perse
motion of the heavens-The celestial pole
Spheres of observation-The Pole-Star and

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CHAPTER II

THE EARTH AS A SPINNING

Early ideas concerning the shape of the earth-
surface-Circular form of the horizon-Dip c
navigation not a proof of the earth's curv
shadow-Altitudes of the same stars observ
Succession of day and night--All bodies
earth's centre-Daily motion of the sun
ideas as to the sun's motion-The Copernica
pendulum experiment-Exact period of r
Why stars are not seen in the daytime-
The earth's polar and equatorial diameter:
pression