Abstract
THE rapid development of wireless telegraphy which has taken place in the last few years has called forth many articles in the scientific and technical papers, but as yet but few single treatises or text-books. Prof. Braun is known as an experimenter in this branch of electrical science, and the pamphlet under notice treats of the subject from a more or less popular point of view and also gives a short sketch of some of Prof. Braun's own experiments. The first chapter is an interesting historical résumé of the endeavours to signal over a distance without the use of intervening wires. It is interesting to observe that the discovery that the earth could serve as a return conductor for the ordinary telegraph first led up to the thought that the other wire could also be replaced by the earth or air or other medium. In one point we think Prof. Braun's remarks are hardly in agreement with the latest of our ideas—we mean in his description of the Becquerel and radium rays as being of the nature of light and electric waves. This is hardly in accordance with the corpuscle theory, which approaches, as near as it is possible at present, to an explanation of these phenomena. The chapter after this historical introduction deals with the author's own experiments on hydrotelegraphy. The guiding idea of the work was to use the property of an alternating current, with sufficiently high frequency, to flow only on the surface of a conductor. If, now, such a current be led in and out at two points of a sheet of water, the current, instead of penetrating deep down, will tend to spread itself out upon the surface of the water, and by connecting a receiving circuit at any two other points, messages can be passed between the two stations. This method of working differs in principle from that of Rathenau and Strecker, who used stationary currents. With this arrangement, if the receiver be connected to two points lying on an equipotential line, i.e. a line drawn at right angles to the current lines, no messages can be received. With Braun's arrangement this is different, due to the fact that the equipotential lines continually change. With experiments made at Cuxhaven, signals could be sent for a distance of three kilometres, it being proved that the effect was neither transmitted through the air nor was it an induction effect similar to Preece's experiments. All the results agree fully with the enunciated principle.
Drahtlose Telegraphie durch Wasser und Luff.
Based on Lectures delivered in the Winter of 1900 by Prof. Dr. Ferdinand Braun., Director of the Physical Institute of the University of Strassburg. Pp. 68. (Leipzig: Veit and Co., 1901.) Price M. 2.
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G., C. Drahtlose Telegraphie durch Wasser und Luff . Nature 64, 497 (1901). https://doi.org/10.1038/064497a0
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DOI: https://doi.org/10.1038/064497a0