Gauss, Carl Friedrich (1839). “Allgemeine Theorie des Erdmagnetismus [General theory of terrestrial magnetism]”. Trong Gauss, Carl Friedrich; Weber, Wilhelm (biên tập). Resultate aus den Beobachtungen des Magnetischen Vereins im Jahre 1838 [Findings from the Observations of the Magnetic Society in the Year 1838] (bằng tiếng German). Leipzig, (Germany): Weidmanns' Bookshop. tr. 1–57.Quản lý CS1: ngôn ngữ không rõ (liên kết) Gauss speculated that magnetic forces might be generated not only by electrical currents flowing through the Earth's interior but also by some sort of electrical current(s) flowing through the atmosphere. From p. 50: "§ 36. Ein anderer Theil unserer Theorie, über welchen ein Zweifel Statt finden kann, ist die Voraussetzung, ... zu untersuchen , wie die aus denselben hervorgehende magnetische Wirkung auf der Erdoberfläche sich gestalten würde." (Another part of our theory about which doubt may arise is the assumption that the agents of terrestrial magnetic force have their source exclusively in the interior of the Earth. If the immediate causes [of terrestrial magnetism] should be sought entirely or in part outside [the Earth's interior], then we can — in so far as we exclude baseless fantasies and we want to restrict ourselves to the scientifically known [facts] — consider only galvanic currents. Atmospheric air is not a conductor of such currents; empty space also is not: thus our knowledge fails us when we seek a carrier for galvanic currents in the upper regions [of the atmosphere]. Only the enigmatic phenomena of the northern lights — in which by all appearances electricity in motion plays a major role — prohibits us from simply denying the possibility of such currents just on account of that ignorance, and in any case it remains interesting to investigate how the magnetic effect resulting from [those currents] would manifest itself on the Earth's surface.)
English translation: Gauss, Carl Friedrich; Sabine, Elizabeth Juliana, trans. (1841). “General theory of terrestrial magnetism”. Trong Taylor, Richard (biên tập). Scientific Memoirs, Selected from the Transactions of Foreign Academies of Science and Learned Societies, and from Foreign Journals. London, England: Richard and John E. Taylor. tr. 184–251.
Heaviside, Oliver (1902). “Telegraphy”. Encyclopaedia Britannica. 33 (ấn bản 10). tr. 213–235. Speaking of wireless telegraphy, Heaviside speculated about the propagation of Hertzian (radio) waves through the atmosphere. From p. 215: "There may possibly be a sufficiently conducting layer in the upper air. If so, the waves will, so to speak, catch on to it more or less. Then the guidance will be the sea on one side and the upper layer on the other."
