We might also find in certain works earlier than the experiments of Hertz attempts at transmission in which, unconsciously no doubt, phenomena were already set in operation which would, at this day, be classed as electric oscillations. It is allowable no doubt, not to speak of an American quack, Mahlon Loomis, who, according to Mr Story, patented in 1870 a project of communication in which he utilised the Rocky Mountains on one side and Mont Blanc on the other, as gigantic antennae to establish communication across the Atlantic; but we cannot pass over in silence the very remarkable researches of the American Professor Dolbear, who showed, at the electrical exhibition of Philadelphia in 1884, a set of apparatus enabling signals to be transmitted at a distance, which he described as “an exceptional application of the principles of electrostatic induction.” This apparatus comprised groups of coils and condensers by means of which he obtained, as we cannot now doubt, effects due to true electric waves.
Place should also be made for a well-known inventor, D.E. Hughes, who from 1879 to 1886 followed up some very curious experiments in which also these oscillations certainly played a considerable part. It was this physicist who invented the microphone, and thus, in another way, drew attention to the variations of contact resistance, a phenomenon not far from that produced in the radio-conductors of Branly, which are important organs in the Marconi system. Unfortunately, fatigued and in ill-health, Hughes ceased his researches at the moment perhaps when they would have given him final results.
In an order of ideas different in appearance, but closely linked at bottom with the one just mentioned, must be recalled the discovery of radiophony in 1880 by Graham Bell, which was foreshadowed in 1875 by C.A. Brown. A luminous ray falling on a selenium cell produces a variation of electric resistance, thanks to which a sound signal can be transmitted by light. That delicate instrument the radiophone, constructed on this principle, has wide analogies with the apparatus of to-day.
Starting from the experiments of Hertz, the history of wireless telegraphy almost merges into that of the researches on electrical waves. All the progress realised in the manner of producing and receiving these waves necessarily helped to give rise to the application already indicated. The experiments of Hertz, after being checked in every laboratory, and having entered into the strong domain of our most certain knowledge, were about to yield the expected fruit.
Experimenters like Sir Oliver Lodge in England, Righi in Italy, Sarrazin and de la Rive in Switzerland, Blondlot in France, Lecher in Germany, Bose in India, Lebedeff in Russia, and theorists like M.H. Poincare and Professor Bjerknes, who devised ingenious arrangements or elucidated certain points left dark, are among the artisans of the work which followed its natural evolution.