Direct Current Geoelectric Sounding: Principles and Interpretation provides a comprehensive review of the Schlumberger method of geoelectric sounding, as well as current methods of interpretation. It explores the theoretical foundations of geoelectric sounding, the relative advantages and limitations of the two symmetrical arrangements for vertical electrical sounding, the techniques of interpretation for Wenner sounding curves, and dipole sounding. This volume is based on educational materials used in the study of geoelectric sounding. It begins with an overview of the theory of current flow in a horizontally stratified Earth, followed by a discussion of how the resistivity of the ground is measured. The book explains the current flow in a homogeneous anisotropic and horizontally stratified Earth, the principle of equivalence, and vertical electrical sounding. Moreover, it presents the basic principles and procedures for the construction of theoretical master curves. Asymptotic values of Schlumberger curves, the principle of reduction of two layers and of a three-layer Earth, and Tagg's method of interpretation are also discussed. The book explains the interpretation by curve-matching, characteristics of dipole electric sounding, and geological applications of electrical resistivity sounding. Engineering problems and application examples with self-explanatory diagrams are provided at the end of the chapters. This book will benefit undergraduate and postgraduate students who want to broaden their understanding of exploration geophysics, as well as professional exploration geologists and geophysicists, civil engineers, agricultural scientists, and researchers.