G., McGill University, Canada, 68. * Wilson, G. W., & Co., Aberdeen, Scotland, 82, 213. * Worsley-Benison, F. H., Cheapstow, England, 170. * Dealer in photographs or lantern slides. CONTENTS Page Introduction.--The Scope And Aim Of Geology 1 PART I EXTERNAL GEOLOGICAL AGENCIES Chapter I. The Work Of The Weather 5 II. The Work Of Ground Water 39 III. Rivers And Valleys 54 IV. River Deposits 93 V. The Work Of Glaciers 113 VI. The Work Of The Wind 144 VII. The Sea And Its Shores 155 VIII. Offshore And Deep-Sea Deposits 174 PART II INTERNAL GEOLOGICAL AGENCIES IX. Movements Of The Earth's Crust 195 X. Earthquakes 233 XI. Volcanoes 238 XII. Underground Structures Of Igneous Origin 265 XIII. Metamorphism And Mineral Veins 281 PART III HISTORICAL GEOLOGY XIV. The Geological Record 291 XV. The Pre-Cambrian Systems 304 XVI. The Cambrian 315 XVII. The Ordovician And Silurian 327 XVIII. The Devonian 341 XIX. The Carboniferous 350 XX. The Mesozoic 368 XXI. The Tertiary 394 XXII. The Quaternary 416 INDEX 451 THE ELEMENTS OF GEOLOGY INTRODUCTION THE SCOPE AND AIM OF GEOLOGY Geology deals with the rocks of the earth's crust. It learns from their composition and structure how the rocks were made and how they have been modified. It ascertains how they have been brought to their present places and wrought to their various topographic forms, such as hills and valleys, plains and mountains. It studies the vestiges which the rocks preserve of ancient organisms which once inhabited our planet. Geology is the history of the earth and its inhabitants, as read in the rocks of the earth's crust.