2. Commercial (financial) control of the mineral resources of the world 64 3. Political (territorial) control of the mineral resources of the world 64 4. The fertilizer situation in the United States 100 5. Diagram showing the chemical composition and heat efficiency of the several ranks of coal 122 6. Origin and development of coal 123 7. Chart showing the present tendency of the United States in respect to its unmined reserve of petroleum 134 8. The annual output of the principal oil fields of the United States for the last twenty years 135 9. Curve showing the usual decline in oil field production after the period of maximum output is reached 136 10. Chart showing the relative values of the principal petroleum products manufactured in the United States from 1899 to 1914 138 11. Alteration of Lake Superior iron formation to iron ore by the leaching of silica 168 12. Representing in terms of weight the mineralogical changes in the katamorphism of serpentine rocks to iron ore, eastern Cuba 172 13. Diagram showing gradation from syenite to bauxite in terms of volume 245 CHAPTER I INTRODUCTION SURVEY OF FIELD In adapting ourselves to physical environment it has been necessary to learn something about the earth. Mainly within the last century has this knowledge been organized into the science of geology, and only within the last few decades have the complex and increasing demands of modern civilization required the applications of geology to practical uses, resulting in the development of the science generally known as _economic geology_. This science is not sharply marked off from the science of geology proper; almost any phase of geology may at some time or some place take on its economic aspect. The usefulness of economic geology was first recognized in relation to mineral resources,--and particularly in relation to metallic resources, their discovery and development,--but the science has been found to have much wider practical application. The practice of the economic geologist in recent years has taken on many new phases.