The idea of utilising such a very interesting phenomenon as an indicator in the study of the Hertzian waves seems to have occurred simultaneously to several physicists, among whom should be especially mentioned M. Ed. Branly himself, Sir Oliver Lodge, and MM. Le Royer and Van Beschem, and its use in laboratories rapidly became quite common.
The action of the waves on metallic powders has, however, remained some what mysterious; for ten years it has been the subject of important researches by Professor Lodge, M. Branly, and a very great number of the most distinguished physicists. It is impossible to notice here all these researches, but from a recent and very interesting work of M. Blanc, it would seem that the phenomenon is allied to that of ionisation.
The history of wireless telegraphy does not end with the first experiments of Marconi; but from the moment their success was announced in the public press, the question left the domain of pure science to enter into that of commerce. The historian’s task here becomes different, but even more delicate; and he will encounter difficulties which can be only known to one about to write the history of a commercial invention.
The actual improvements effected in the system are kept secret by the rival companies, and the most important results are patriotically left in darkness by the learned officers who operate discreetly in view of the national defence. Meanwhile, men of business desirous of bringing out a company proclaim, with great nourish of advertisements, that they are about to exploit a process superior to all others.
On this slippery ground the impartial historian must nevertheless venture; and he may not refuse to relate the progress accomplished, which is considerable. Therefore, after having described the experiments carried out for nearly ten years by Marconi himself, first across the Bristol Channel, then at Spezzia, between the coast and the ironclad San Bartolommeo, and finally by means of gigantic apparatus between America and England, he must give the names of those who, in the different civilised countries, have contributed to the improvement of the system of communication by waves; while he must describe what precious services this system has already rendered to the art of war, and happily also to peaceful navigation.
From the point of view of the theory of the phenomena, very remarkable results have been obtained by various physicists, among whom should be particularly mentioned M. Tissot, whose brilliant studies have thrown a bright light on different interesting points, such as the role of the antennae. It would be equally impossible to pass over in silence other recent attempts in a slightly different groove. Marconi’s system, however improved it may be to-day, has one grave defect. The synchronism of the two pieces of apparatus, the transmitter and the receiver, is not perfect, so that