SCIENCE IN THE INDUSTRIAL WORLD 



tance of almost 1550 miles from the sending point, these 

 messages being actually in words and not mere prede- 

 termined signals. Mere signaling could be determined at 

 a distance something over two thousand miles. On this 

 eventful voyage the fact was established by Marconi 

 that such messages could only be received by a vessel, 

 or vessels, tuned to the same electrical pitch as the shore 

 instrument, and that no insurmountable interference 

 would be offered by messages of a different pitch 

 passing through the atmosphere at the same time. This 

 was established by the fact that several other vessels 

 equipped with Marconi instruments, but keyed to a 

 different electrical pitch, had been on the ocean at the 

 same time, and had been sending messages continually 

 during the passage. The Umbria, for example, had been 

 nearer the sending station, and in the same receiving 

 zone as the Philadelphia, and yet she had neither re- 

 ceived these messages nor had her own messages been 

 interfered with by them. 



This seemed to establish Marconi's contention, which 

 had heretofore been greatly doubted, that different sets 

 of instruments might be worked within short distances of 

 each other within distances of five inches, the inventor 

 said without interfering with each other; and his 

 messages were assured against possible "tapping of the 

 circuit," by the two hundred and fifty different "tun- 

 ings" that he was able to give his instrument. "It 

 seems to be a matter of popular belief," wrote Marconi, 

 "that any receiver within effective range of the transmit- 

 ter is capable of tapping each message sent, or in other 

 words, that there can be no secrecy of communica- 



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