IN 1924 the International Research Council (now transformed into the International Council of Scientific Unions) formed a Commission for the Study of Solar and Terrestrial Relationships, a field of science which extends over the domains of at least three of the International Scientific Unions. This Commission, among other activities, has published triennial reports, reviewing the state and progress of knowledge on solar and terrestrial relationships, and, where necessary, making recommendations regarding action that may conduce to further progress. These reports are distributed to certain libraries and to institutions and individuals occupied in work relating to the subject. The fourth report has recently been issued (Conseil International des Unions Scientifiques: Quatrieme Rapport de la Commission pour PEtude des Relations entre les Phenomenes Solaires et Terrestres; pp. 159. Firenze, 1936) under the editorship of the president of the Commission, Prof. G. Abetti, Astrophysical Observatory, Arcetri, Italy. It differs from its predecessors in being better and more attractively produced, and in having a valuable 28-page introduction by the editor, giving a general survey of the subject for the past three years. The remainder of the volume consists of twenty-one brief articles on different aspects of the subject, by various authors.