Problems of current interest relating to the earth's physical history will be discussed in this volume. Each chapter constitutes a subject in itself, but the sequence I have chosen will, I hope, show and explain the deeper correlation of several terrestrial pro­ cesses which, at first sight, appear to be heterogeneous. The geologist follows the changing face of the earth, the oscillations of the sea-level, the pulsation of folding and mountain-building, the periodicity of the ice-ages, the rhythmical cadence of Life. Just as the physician will draw his conclttsions from outward symptoms when examining his patient, so the geologist tries to discover the deeper significance of the sequence of observed phenomena by ieeling the pulse of the earth. The many additions and revisions which have had to be made in this second. edition include three new chapters, several new sections in other chapters, I09 new textfigures, I2 tables and 2 plates. A leu) fundamental geological terms have been explained in Chapter I.