SALEM, MASSACHUSETTS, October, 1906. CONTENTS Page I. INTRODUCTION 1 II. IMMEASURABLE DISTANCES OF SPACE 7 III. OTHER WORLDS INHABITED 14 IV. LOWELL'S BOOK ON MARS 31 V. TESTIMONY OF ASTRONOMERS 51 VI. THE STUDY OF PLANETARY MARKINGS 70 VII. DIFFICULTIES OF SEEING 79 VIII. VARIATION IN DRAWING 94 IX. THEORIES REGARDING THE CANALS 100 X. COMMENTS AND CRITICISM 125 XI. ATMOSPHERE AND MOISTURE 134 XII. NOTES ON IRRIGATION 141 XIII. VARIETY OF CONDITIONS UNDER WHICH LIFE EXISTS 147 XIV. MY OWN WORK 158 XV. WHAT THE MARTIANS MIGHT SAY OF US 166 XVI. SCHIAPARELLI, LOWELL, PERROTIN, THOLLON 172 XVII. LAST WORDS 180 INDEX 189 LIST OF ILLUSTRATIONS LOWELL'S GLOBE OF MARS _Frontispiece_ Fig. 1. PLANISPHERE OF EARTH _Page_ 61 PLATES I. TOBACCO CULTIVATION UNDER CLOTH, PORTO RICO _Page_ 50 II. DRAWINGS OF SOLAR CORONA " 96 III. CHINESE BOWL, SHOWING CRACKLE " 107 IV. MUD CRACKS ON SHORE OF ROGER'S LAKE, ARIZONA " 108 V. NATURAL LINES, CRACKS, FISSURES, ETC. " 112 VI. ARTIFICIAL LINES, RAILWAYS, STREETS, CANALS, ETC. " 113 VII. DOME OF LOWELL OBSERVATORY, FLAGSTAFF, ARIZONA " 158 VIII. TWENTY-FOUR INCH TELESCOPE, LOWELL OBSERVATORY " 160 IX. DRAWINGS OF CANALS OF MARS BY THE AUTHOR " 162 PORTRAITS GIOVANNI VIRGINIO SCHIAPARELLI _Page_ 172 PERCIVAL LOWELL " 174 HENRI PERROTIN " 176 M. THOLLON " 178 _Life not wholly unlike that on the earth may therefore exist upon Mars for anything we know to the contrary._ SIMON NEWCOMB. MARS AND ITS MYSTERY I INTRODUCTION