Oliver Heaviside and the Heaviside layer

In an entry in the Encyclopaedia Britannica in 1902, Oliver Heaviside had suggested the existence of a reflecting layer in the upper atmosphere to account for long range beyond line-of-sight radio propagation of the type demonstrated by Guglielmo Marconi in 1901, in the first transatlantic radio transmission. In about 1910, William Eccles proposed the name 'Heaviside Layer' for this phenomenon, and the name has subsequently been adopted and used quite widely. This paper describes the basis of Marconi's experiments and various interpretations of the results in the context of Heaviside's wider work. It also describes some later experiments to measure the height of the ionosphere.This article is part of the theme issue 'Celebrating 125 years of Oliver Heaviside's 'Electromagnetic Theory''.