As important to modern world views as any work of Darwin, Marx, or Freud, Principles of Geology is a landmark in the history of science. In this first of three volumes, Charles Lyell (1797-1875) sets forth his powerful uniformitarian argument: processes now visibly acting in the natural world are essentially the same as those that have acted throughout the history of the earth, and are sufficient to account for all geological phenomena. Martin J. S. Rudwick\'s new Introduction, summarizing the origins of the Principles, guides the reader through the structure of the entire three-volume first edition and considers the legacy of Lyell\'s great work.