The construction of communism requires the increasingly effective incorporation of natural resources into economic circulation and the ever broader utilization of natural conditions. A comprehensive and scientific understanding of the laws and characteristics of natural development in the various regions of our country contributes to the solution of these tasks. The series of monographs entitled Natural Conditions and Natural Resources of the USSR is a comprehensive work summarizing modern knowledge of nature and natural resources in the major regions of the Soviet Union. Unlike publications that describe individual aspects of nature and various types of natural resources, such as Geology of the USSR and Climate of the USSR, this scientific series summarizes contemporary understanding of regional complexes of natural conditions and their associated combinations of natural resources. It synthesizes the results of research on the physical geography of the Soviet territory conducted during the Soviet era, provides a scientific characterization of natural conditions and natural resources, and outlines the principal approaches to their rational and efficient utilization. These monographs are not intended to replace the numerous reference works available, nor can they be expected to cover every issue exhaustively. They reflect the current state of knowledge and, naturally, the differing degrees to which various elements of the geographical environment have been studied, as well as the existence of differing views concerning certain natural phenomena and processes. All of this enables us to make sound judgments regarding possible solutions to particular scientific and economic problems and to identify directions for further scientific research. The volume in this series devoted to the Cis-Baikal and Trans-Baikal regions (the Irkutsk and Chita Oblasts and the Buryat Autonomous Soviet Socialist Republic) is a collective work prepared by more than thirty authors representing fifteen research institutions and institutions of higher education located in Moscow, Irkutsk, Ulan-Ude, and Chita. It must be emphasized that such a detailed monographic description of a remote region, which before the Great October Socialist Revolution had been among the least studied parts of our country, became possible only because of the enormous efforts undertaken by the Communist Party of the Soviet Union and the Soviet Government in establishing a network of scientific institutions dedicated to the study of natural resources and all aspects of the development and utilization of natural conditions. The preparation of this work was directed by the Institute of Geography of the Academy of Sciences of the USSR. The development of the working plan and the overall editorial organization of this volume were carried out by V. S. Preobrazhensky (В. С. Преображенский).