Geysers. What makes them work? Many who have seen a geyser in action know only that it spouts hot water into the air. Many others have never seen one. Chapter 1, Geysers of the World, delineates their distinguishing features, locates the geyser regions of the world, and places investigations by world travelers and scientists in historic perspective. One of the quickest ways to become acquainted with a geyser is to observe it. The descriptions of several well known geysers, some based on past observations by others, but frequently by me, do not necessarily portray current behavior. They do, however, represent general features. Geysers exist as a result of a delicate and unique interplay among the heat, the water, and the rocks of the earth. In essence, heat and water must be available, transported, distributed, stored, and finally released. This book brings together most aspects of geyser activity. It differs from past discussions, which though extensive and excellent have either been guide books or limited expositions of a single geyser area or phenomenon. Here information from all of the geyser areas of the world is used to establish the causes, nature, and effects of geyser activity. In preparing this book, available geyser literature has been drawn on heavily, often simply paraphrased. Only figures and tables are referenced specifically. All material consulted is listed in the bibliography with each chapter's references identified. All of the major works contain additional and sometimes extensive bibliographies for further study.