1. Introduction.- 2. Fundamentals of Geothermics.- 2.1. Definitions, Standards, Conversions.- 2.2. Equations of Heat Conduction.- 2.2.1. Fourier Equations.- 2.2.2. Laplace and Poisson Equations.- 2.2.3. Cylindrical and Spherical Coordinates.- 2.3. Equations of Heat Convection.- 2.3.1. Introductory Remarks.- 2.3.2. Analytical Solutions.- 2.3.3. Recognition of Water Movements.- 2.4. Numerical Methods.- 2.4.1. Finite-Difference Method (FDM).- 2.4.2. Finite-Element Method (FEM).- 2.5. Summary of Recommendations.- 2.6. References.- 3. Determination of Virgin Rock Temperatures.- 3.1. Introduction.- 3.2. Sensors for Measurements.- 3.2.1. Types of Sensor.- 3.2.2. Calibration of Field Sensors.- 3.3. Measurements of Subsurface Temperatures in Boreholes.- 3.3.1. Resistance Measuring Technique.- 3.3.2. Frequency Measuring Technique.- 3.3.3. Precautions for Maintaining Accuracy of Depth Measurement.- 3.3.4. Protection of the Sensing Head from a Hostile Environment.- 3.3.5. Continuous Logging of Temperature.- 3.4. Perturbations due to Convection.- 3.5. Data from Holes that are Thermally Perturbed by Drilling Fluids.- 3.5.1. Use of Bottom Hole Temperatures.- 3.5.2. Boreholes that are not in Equilibrium.- 3.6. Data from Boreholes with Hydraulically Driven Water Flows.- 3.7. Measurements of Temperatures in Lake and Oceanic Sediments.- 3.8. Measurements in Mines and Tunnels.- 3.9. Summary of Recommendations.- 3.10. References.- 4. Thermal Properties.- 4.1. Methods for Determining Thermal Conductivity and Thermal Diffusivity.- 4.1.1. Introduction.- 4.1.2. Steady State Methods for Measuring Thermal Conductivity.- 4.1.3. Transient Techniques for Determining Conductivity and/or Diffusivity.- 4.1.4. Methods of Estimating Thermal Properties from Mineral Content.- 4.1.5. Sources of Experimental Error.- 4.1.6. Standards.- 4.1.7. Summary of Recommendations.- 4.1.8. References.- 4.2. Determination of Heat Production Rate.- 4.2.1. Definitions.- 4.2.2. Measurement Techniques.- 4.2.3. Calibration, Data Processing.- 4.2.4. Accuracy, Precision.- 4.2.5. Sensitivity, Detection Limits.- 4.2.6. Heat Production Rate of Various Rock Types.- 4.2.7. Indirect Methods for Determining Heat Production Rate.- 4.2.8. Summary of Recommendations.- 4.2.9. References.- 4.3. Opacity — The Concept of Radiative Thermal Conductivity.- 4.3.1. Introduction.- 4.3.2. Some Theory.- 4.3.3. Experimental Work on Opacity.- 4.3.4. Summary of Recommendations.- 4.3.5. References.- 5. Continental Heat-Flow Density.- 5.1. Introduction.- 5.2. Determining Continental Heat-Flow Density.- 5.2.1. Interval Method.- 5.2.2. Bullard Method.- 5.3. Reporting Uncertainties in Heat-Flow Density Determinations.- 5.4. Terrain Effects and Palaeoclimatic Corrections.- 5.4.1. Description of Effects — Steady State.- 5.4.2. Correction Techniques — Steady State.- 5.4.3. Transient Effects and Corrections.- 5.5. Groundwater Disturbances.- 5.6. Perturbations due to Free Convection.- 5.7. Summary of Recommendations.- 5.8. References.- 6. Oceanic Heat-Flow Density.- 6.1. Introduction.- 6.1.1. Ridgecrest Problems.- 6.1.2. Continental Margin Problems.- 6.1.3. Old Ocean Basin Problems.- 6.2. Contemporary Instrumentation.- 6.3. Shipboard Operation.- 6.4. Data Reduction.- 6.4.1. Penetration Heating Extrapolation.- 6.4.2. In-situ Thermal Conductivity.- 6.4.3. Heat-Flow Density.- 6.4.4. Graphical Data Reduction.- 6.4.5. Long Time Asymptotic Relations.- 6.5. Sources of Errors.- 6.6. Summary of Recommendations.- 6.7. References.- 7. Geothermal Maps.- 7.1. Introduction.- 7.2. General Statements.- 7.2.1. Computer Contouring.- 7.2.2. Visual Contouring.- 7.2.3. Test of Significance.- 7.2.4. Comparison of Individual Techniques.- 7.2.5. Corrections in Geothermal Mapping.- 7.3. Temperature, Temperature Gradient and Heat-Flow Density Maps.- 7.3.1. Temperature Maps.- 7.3.2. Maps of Vertical and Horizontal Temperature Gradient.- 7.3.3. Maps of Heat-Flow Density.- 7.4. Geothermal Resource and Reserve Representation.- 7.4.1. Objectives.- 7.4.2. Assessment and Mapping in Low Enthalpy Areas.- 7.4.3. Assessment and Mapping in High Enthalpy Areas.- 7.5. Summary of Recommendations.- 7.6. References.- 8. Crust and Mantle Geothermics.- 8.1. Thermal Regime of the Lithosphere.- 8.2. References.- 8.3. Downward Continuation.- 8.3.1. Introduction.- 8.3.2. Inverse Problems for Steady-State Heat Conduction Models.- 8.3.3. Linear Inverse Problems.- 8.3.4. Lateral Constraints in Linear Inverse Problems.- 8.3.5. Determination of Mantle Heat-Flow Density.- 8.3.6. Optimal Heat Source.- 8.4. References.- 9. Implications.- 9.1. Geodynamics.- 9.1.1. Introduction.- 9.1.2. Global Heat Output.- 9.1.3. Oceanic Heat-Flow Density.- 9.1.4. Continental Heat-Flow Density.- 9.1.5. Heat-Flow Density and Lithospheric Structures.- 9.1.6. Thermal Processes in Orogenic Zones.- 9.1.7. Thermal Process at Transform Faults.- 9.1.8. Geothermics of Sedimentary Basins.- 9.1.9. Heat-Flow Density Anomaly Associated with Intraplate Heat Sources.- 9.1.10. Temperature Distribution in the Earth.- 9.1.11. Thermal History of the Earth.- 9.1.12. Final Words.- 9.1.13. References.- 9.2. Thermal Exploration Methods.- 9.2.1. Introduction.- 9.2.2. Energy Exploration.- 9.2.3. Non-Energy Exploration.- 9.2.4. References.- 9.3. Palaeogeothermics.- 9.3.1. Introduction.- 9.3.2. Palaeogeothermics Based on Maturation of Organic Materials in Sediments.- 9.3.3. Homogenization Temperature Method (Microthermometry).- 9.3.4. Other methods.- 9.3.5. References.- 9.4. Engineering Applications.- 9.4.1. Introduction.- 9.4.2. Subsurface Temperature Distribution.- 9.4.3. Practical Aspects of Heat Transport by Convection.- 9.4.4. Permafrost.- 9.4.5. Manipulation of Subsurface Temperatures by Technical Installations.- 9.4.6. Storage of Heat Producing Wastes in the Underground.- 9.4.7. References.- 10. Appendix.- 10.1. Thermal Conductivity.- 10.2. Palaeotemperatures.- 10.3. References.- 10.4. Glossary of Symbols.- 10.5. Computer Programme to Section 4.3.3..- Author Index.