It is hoped that this book will be of value to many different classes of men engaged in the search for mineral deposits. These classes might include the experienced practical prospector who would like to learn something of geology; the young geologist who needs information on practical prospecting; the novice who needs a comprehensive reference; and the all around experienced exploration engineer or geologist who might need to refer to some specialized technique, look up a reference in the bibliography, or read a resume of the geology of a particular area, Because this book is aimed at so many different classes, different chapters are written assuming different levels of learning and experience. This, no doubt, will prove troublesome at times, but it is believed to be the best way to insure that the information contained in each chapter will reach with maximum effectiveness the group for whom it is intended