The scope of the book precludes the possibility of furnishing the reader with the sources for the body of fact and theory which is presented, although much may be inferred from the names which appear beneath the illustrations, and more definite knowledge will be found in the references to literature supplied at the ends of chapters. A large amount of original and unpublished material is for a similar reason unlabeled, and it has been left for the professional geologist to detect these new strands which have been drawn into the web. WILLIAM HERBERT HOBBS. ANN ARBOR, MICHIGAN, October 25, 1911. CONTENTS CHAPTER I THE COMPILATION OF EARTH HISTORY PAGE The sources of the history—Subdivisions of geology—The study of earth features and their significance—Tabular recapitulation—Geological processes not universal—Change, and not stability, the order of nature—Observational geology _versus_ speculative philosophy—The scientific attitude and temper—The value of the hypothesis—Heading references 1 CHAPTER II THE FIGURE OF THE EARTH The lithosphere and its envelopes—The evolution of ideas concerning the earth’s figure—The oblateness of the earth—The arrangement of oceans and continents—The figure toward which the earth is tending—Astronomical _versus_ geodetic observations—Changes of figure during contraction of a spherical body—The earlier figures of the earth—The continents and oceans at the close of the Paleozoic era—The flooded portions of the present continents—The floors of the hydrosphere and atmosphere—Reading references 8 CHAPTER III THE NATURE OF THE MATERIALS IN THE LITHOSPHERE The rigid quality of our planet—Probable composition of the earth’s core—The earth a magnet—The chemical constitution of the earth’s surface shell—The essential nature of crystals—The lithosphere a complex of interlocking crystals—Some properties of natural crystals, minerals—The alterations of minerals—Reading references 20 CHAPTER IV THE ROCKS OF THE EARTH’S SURFACE SHELL The processes by which rocks are formed—The marks of origin—The metamorphic rocks—Characteristic textures of the igneous rocks—The classification of rocks—Subdivisions of the sedimentary rocks—The different deposits of ocean, lake, and river—Special marks of littoral deposits—The order of deposition during a transgression of the sea—The basins of deposition of earlier ages—The deposits of the deep sea—Reading references 30 CHAPTER V CONTORTIONS OF THE STRATA WITHIN THE ZONE OF FLOW