The constantly growing demand for energy, as well as the realization during the past decade that fossil energy reserves to satisfy ever- increasing energy consumption are limited, have helped, as part of the search for alternative energy sources, to bring the subject of geothermics to its present level of significance. Practical geothermics is concerned with prospecting for and develop- ment of geothermal heat. General geothermics deals with the thermal state of our Earth as a whole. Both divisions of this field, however, contribute practical insights, and improved methods of temperature...