Even to the technical student, a popular book, if well done, may yield most valuable results. For nothing in any branch of science is so little known as its articulation,—how the skeleton of it is put together, and what may be the mode of attachment of its muscles. CONTENTS PAGE PREFACE vii PART I NATURAL FEATURES CHAPTER I. ON EXPLORATION 3 II. A DEPARTURE-POINT 12 III. A BIRD’S-EYE VIEW OF PAST MARTIAN DISCOVERY 20 IV. THE POLAR CAPS 32 V. BEHAVIOR OF THE POLAR CAPS 41 VI. MARTIAN POLAR EXPEDITIONS 54 VII. WHITE SPOTS 73 VIII. CLIMATE AND WEATHER 82 IX. MOUNTAINS AND CLOUD 96 X. THE BLUE-GREEN AREAS 108 XI. VEGETATION 119 XII. TERRAQUEOUSNESS AND TERRESTRIALITY 128 XIII. THE REDDISH-OCHRE TRACTS 148 XIV. SUMMARY 159 PART II NON-NATURAL FEATURES XV. THE CANALS 173 XVI. THEIR SYSTEM 184 XVII. GEMINATION OF THE CANALS 192 I. THE DIPLOPIC THEORY 196 II. THE INTERFERENCE THEORY 201 III. THE ILLUSION THEORY 202 XVIII. THE DOUBLE CANALS 204 XIX. CANALS IN THE DARK REGIONS 243 XX. OASES 249 XXI. CARETS ON THE BORDERS OF THE GREAT DIAPHRAGM 265 XXII. THE CANALS PHOTOGRAPHED 271 PART III THE CANALS IN ACTION XXIII. CANALS: KINEMATIC 281 XXIV. CANAL DEVELOPMENT INDIVIDUALLY INSTANCED 304 XXV. HIBERNATION OF THE CANALS 313 XXVI. ARCTIC CANALS AND POLAR RIFTS 325 XXVII. OASES: KINEMATIC 330 PART IV EXPLANATION