Rept. Geol. Surv. Mich.: Report of the Geological Survey of Michigan, Lansing. Rept. Mich. Acad. Sci.: Report of the Michigan Academy of Science, Lansing. Rept. Nat. Conserv. Com.: Report of the National Conservation Commission, Washington. Rept. Smithson. Inst.: Report of the Smithsonian Institution, Washington. Sci. Bull. Brooklyn Inst. Arts and Sci.: Science Bulletin of the Brooklyn Institute of Arts and Sciences. Scot. Geogr. Mag.: Scottish Geographic Magazine, Edinburgh. Smith. Cont. to Knowl.: Smithsonian Contributions to Knowledge, Washington. Tech. Quart.: Technology Quarterly of the Massachusetts Institute of Technology, Boston. Trans. Am. Inst. Min. Eng.: Transactions of the American Institute of Mining Engineers, New York. Trans. Roy. Dublin Soc.: Transactions of the Royal Dublin Society. Trans. Seis. Soc. Japan: Transactions of the Seismological Society of Japan, Tokyo. Trans. Wis. Acad. Sci.: Transactions of the Wisconsin Academy of Sciences, Arts, and Letters, Madison. U. S. Geogr. and Geol. Surv. Rocky Mt. Region: United States Geographical and Geological Survey of the Rocky Mountain Region (Powell), Washington. Zeit. d. Gesell. f. Erdk. z. Berlin: Zeitschrift der Gesellschaft für Erdkunde zu Berlin. Zeit. f. Gletscherk: Zeitschrift für Gletscherkunde, Berlin. EARTH FEATURES AND THEIR MEANING CHAPTER I THE COMPILATION OF EARTH HISTORY =The sources of the history.=—The science which deals with the chapters of earth history that antedate the earliest human writings is geology. The pages of the record are the layers of rock which make up the outer shell of our world. Here as in old manuscripts pages are sometimes found to be missing, and on others the writing is largely effaced so as to be indistinct or even illegible. An intelligent interpretation of this record requires a knowledge of the materials and the structure of the earth, as well as a proper conception of the agencies which have caused change and so developed the history. These agencies in operation are physical and chemical processes, and so the sciences of physics and chemistry are fundamental in any extended study of geology. Not only is geology, so to speak, founded upon chemistry and physics, but its field overlaps that of many other important sciences. The earliest earth history has to do with the form, size, and physical condition of a minor planet in the solar system. The earliest portion of the story belongs therefore to astronomy, and no sharp line can be drawn to separate this chapter from those later ones which are more clearly within the domain of geology.