The present book commemorates the one-hundredth anniversary of the founding of the American Journal of Science by Benjamin Silliman in July, 1818. The opening chapter gives a somewhat detailed account of the early days of the Journal, with a sketch of its subsequent history. The remaining chapters are devoted to the principal branches of science which have been prominent in the pages of the Journal. They have been written with a view to showing in each case the position of the science in 1818 and the general progress made during the century; special prominence is given to American science and particularly to the contributions to it to be found in the Journal’s pages. References to specific papers in the Journal are in most cases included in the text and give simply volume, page, and date, as (=24=, 105, 1833); when these and other references are in considerable number they have been brought together as a Bibliography at the end of the chapter. The entire cost of the present book is defrayed from the income of the Mrs. Hepsa Ely Silliman Memorial Fund, established under the will of Augustus Ely Silliman, a nephew of Benjamin Silliman, who died in 1884. Certain of the chapters here printed have been made the basis of a series of seven Silliman Lectures in accordance with the terms of that gift. The selection of these lectures has been determined by the convenience of the gentlemen concerned and in part also by the nature of the subject. TABLE OF CONTENTS Page Prefatory Note vii I. The American Journal of Science from 1818 to 1918. Edward Salisbury Dana 13 II. A Century of Geology: The Progress of Historical Geology in North America. Charles Schuchert 60 III. A Century of Geology: Steps of Progress in the Interpretation of Land Forms. Herbert E. Gregory 122 IV. A Century of Geology (continued): The Growth of Knowledge of Earth Structure. Joseph Barrell 153 V. A Century of Government Geological Surveys. George Otis Smith 193 VI. On the Development of Vertebrate Paleontology. Richard Swann Lull 217 VII. The Rise of Petrology as a Science. Louis V. Pirsson 248 VIII. The Growth of Mineralogy from 1818 to 1918. William E. Ford 268 IX. The Work of the Geophysical Laboratory of the Carnegie Institution of Washington. R. B. Sosman 284 X. The Progress of Chemistry during the Past One Hundred Years. Horace L. Wells and Harry W. Foote 288 XI. A Century’s Progress in Physics. Leigh Page 335