. Annual report of the Board of Regents of the Smithsonian Institution. Smithsonian Institution; Smithsonian Institution. Archives; Discoveries in science. 266 WIRELESS TELEGRAPHY. Fig. 4. -Details of Marconi's transmitting svstein. While Dr. Lodge has since done important work in connection with wireless telegraphy, he was, at the time mentioned, presumably more absorbed in the subject from the purely scientific standpoint than otherwise, and although he then, in 1894, intimated that signals might be transmitted to a distance of half a mile by Hertzian waves, it was not until Marconi began hi
. Annual report of the Board of Regents of the Smithsonian Institution. Smithsonian Institution; Smithsonian Institution. Archives; Discoveries in science. 266 WIRELESS TELEGRAPHY. Fig. 4. -Details of Marconi's transmitting svstein. While Dr. Lodge has since done important work in connection with wireless telegraphy, he was, at the time mentioned, presumably more absorbed in the subject from the purely scientific standpoint than otherwise, and although he then, in 1894, intimated that signals might be transmitted to a distance of half a mile by Hertzian waves, it was not until Marconi began his memorable work that really practical results were obtained. In the operation of his wireless telegraph system Marconi uses an electric oscillator (figs. 4 and 5), the Branly coherer k, the Lodge tapper /, in a local circuit, and the Poppott' vertical wire A, at the sending and receiving stations, all of which devices, as has been shown, were well known, and it has been by modify- ing, improving, and perfecting these devices, and by adding others, that Marconi has been enabled to obtain his excellent practical results. The im- provements and additions that have, perhaps, conduced more than anything else to the first successful results ob- tained by Marconi were those that re- lated to the coherer and the vertical wire. The sensitiveness of the coherer he increased greatly by diminishing its size, compared with the Branly coherer, and by employing a mixture of nickel filings and silver—90 per cent of the former and 10 per cent of the latter metal. He also placed the few filings used in a vacuum. The other instru- ments, shown in fig. 5, are the relay, R, controlled by the coherer, and an ink-recording instrument, E, controlled by the relay. This figure illustrates the earlier arrangement of Marconi's devices. In it the coherer is directly connected with the lower end of the vertical wire by one of its terminids and with the earth by its other terminal. In his later work, Marc
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