Produced by Jonathan Ingram and the Online Distributed Proofreading Team at https://www.pgdp.net (This file was produced from images generously made available by The Internet Archive/American Libraries.) HARPER'S LIBRARY of LIVING THOUGHT ARE THE PLANETS INHABITED? BY E. WALTER MAUNDER, F.R.A.S. SUPERINTENDENT OF THE SOLAR DEPARTMENT, ROYAL OBSERVATORY GREENWICH AUTHOR OF "ASTRONOMY WITHOUT A TELESCOPE" "THE ROYAL OBSERVATORY, GREENWICH, ITS HISTORY AND WORK" "THE ASTRONOMY OF THE BIBLE," "THE HEAVENS AND THEIR STORY" ETC. HARPER & BROTHERS LONDON AND NEW YORK 45 ALBEMARLE STREET, W. 1913 _Published March, 1913_ CONTENTS CHAPTER PAGE I. THE QUESTION STATED 1 II. THE LIVING ORGANISM 6 III. THE SUN 20 IV. THE DISTRIBUTION OF THE ELEMENTS IN SPACE 33 V. THE MOON 43 VI. THE CANALS OF MARS 57 VII. THE CONDITION OF MARS 71 VIII. THE ILLUSIONS OF MARS 96 IX. VENUS, MERCURY AND THE ASTEROIDS 111 X. THE MAJOR PLANETS 122 XI. WHEN THE MAJOR PLANETS COOL 133 XII. THE FINAL QUESTION 143 INDEX 163 ARE THE PLANETS INHABITED? CHAPTER I THE QUESTION STATED The first thought that men had concerning the heavenly bodies was an obvious one: they were lights. There was a greater light to rule the day; a lesser light to rule the night; and there were the stars also. In those days there seemed an immense difference between the earth upon which men stood, and the bright objects that shone down upon it from the heavens above. The earth seemed to be vast, dark, and motionless; the celestial lights seemed to be small, and moved, and shone. The earth was then regarded as the fixed centre of the universe, but the Copernican theory has since deprived it of this pride of place. Yet from another point of view the new conception of its position involves a promotion, since the earth itself is now regarded as a heavenly body of the same order as some of those which shine down upon us. It is amongst them, and it too moves and shines--shines, as some of them do, by reflecting the light of the sun. Could we transport ourselves to a neighbouring world, the earth would seem a star, not distinguishable in kind from the rest.