WIRELESS TELEGRAPHY 



a single wire, no one of which interferes in the 

 least with its neighbors. 



This seems wonderful enough, but, as Wheat- 

 stone showed long ago, the same thing can be 

 done with sound-waves. Wheatstone took a thin, 

 long rod of wood, a quarter of an inch thick, and 

 joined one end to the sounding-board of a piano, 

 the other to a separate sounding-board in a dis- 

 tant room. Here were ten strings, often struck at 

 once. Each vibrates thirty -two times or more, 

 distinctly. The intervening rooms through which 

 the rod ran were silent as a tomb; in the last, all 

 these varied sounds were perfectly and harmoni- 

 ously reproduced. It would need but a sufficient 

 variety of tuning-forks to duplicate the Mercadier 

 multiplex telegraphy with the waves of sound. 



It is rather needless to say that Marconi's 

 splendid demonstration of transoceanic signalling 

 means, in the near future, a big reduction in cable 

 tolls. Marconi himself says that a cent a word is 

 within sight. But even this is a purely arbitrary 

 figure. 



In England, where the public telegraph is not 

 run to enrich rich people, it is possible to send a 

 twelve-word message anywhere in the kingdom 

 for sixpence. From the Marconi station in Corn- 

 wall to London is about two hundred and fifty 



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