Summary of Progress in the Study of Radio Wave Propagation Phenomena

Recent progress in the study of radio wave propagation phenomena is surveyed in the light of the history of the art. The paper is divided into three parts: (A) an historical review; (B) recent developments; and (C) conclusions and outlook for future development. Part A. The historical development of the art from its inception to 1927 is considered. The discussion includes an outline of early isolated sphere hypotheses, their limitations and the development of the modern Kennelly-Heaviside layer theory of radio transmission. Early experimental progress, echo signals, magnetic correlations and the relation of the science of radio direction finding are also considered. Part B. (On recent advances) reviews the progress of the last year or 18 months and includes a discussion of publications on the Störmer-van der Pol echoes and their theoretical interpretation. Progress in Kennelly-Heaviside layer height determinations and experimental studies in transmission and magnetic and solar correlations are also considered. Part C. The rapidity of the advance during the last year is noted, but the need of further consistent observations and other means of investigation before anything approaching a complete satisfactory theory of radio transmission can be evolved is pointed out.