The chemical, physical and physicochemical processes that are at work in the depths of the Earth, both connected and unconnected with man's activities and coupled to the relevant properties and characteristics of the rocks, began to be intensively studied in the early decades of the present century. Until then little evidence had been available concerning the physical and physicochemical properties of rocks, and the data that existed were one-sided and uncoordinated. Both in this country and elsewhere an interest in investigating natural processes, the processes taking place in rocks, and the properties and characteristics of rocks arose as a result of the intensive development of oil and gas engineering, the mining of coal and ore, the construction of large projects, railroads, etc. Information on the properties of rocks was needed, in particular, to facilitate progress in engineering, technology, and geological and geophysical methods of prospecting for extracting and processing mineral deposits. In the late 1920s and early 1930s, methods involving intrinsic and induced pola­ rization were introduced. Moreover, little information was available concerning the petrophysical and petrochemical quantities characterizing the different contribution of various rocks to electrical processes. Electrical methods were followed by other methods of applied physics based on the novel electrical, thermal, magnetic, nuclear, elastic and other properties of rocks.