Geophysical influences on the transmission of wireless waves

The facts of short and long-distance transmission for long and short waves are summarised and the examples of variable signals attributed to the varying phase and amplitude of rays ionically refracted by the upper atmosphere. The diurnal variation of such signals is described, and the strong night signals attributed to a lower atmosphere devoid of excessive ionization. Explanations of the difference between the magnitudes of directional errors for overland and oversea transmission and of the marked success of nocturnal short-wave transmission are put forward. The salient points of the evidence relating to the seasonal variations of signal strength and to the influence of the configuration and inhomogeneity of the earth's surface are also summarised. The facts of wireless telegraphy, as set forth show that the atmosphere exerts a variable but usually favourable influence on wave propagation. This influence may be interpreted in terms of ionic refraction (Eccles) which, to prevent excessive dissipation, must take place at levels sufficiently high to make the mean free paths of the effective carriers larges (Larmor).