1905.] on Recent Advances in Wireless Telegraphy. 37 



wireless telegraphic installations, and also as to what is generally 

 termed " the interception of messages." According to the accepted 

 understanding, " intercepting " a message means or implies securing by 

 force, or by other means, a communication which is intended for some- 

 body else, thereby preventing the intended recipient from receiving it. 

 Now this is just what has never happened in the case of wireless 

 telegraphy. It is quite true that messages are, and have been, 

 tapped or overheard at stations for which they are not intended, but 

 this does not by any means prevent the messages from reaching their 

 proper destination. Of course, if a powerful transmitter giving off 

 strong waves of different frequencies is actuated near one of the 

 receiving stations, it may prevent the reception of messages, but the 

 party working the so-called interfering station is at the same time 

 unable to read the message he is trying to destroy, and therefore, 



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the message is not, in the popular sense of the word, " intercepted." 

 It should be remembered that any telegraph or telephone wire can 

 be tapped, or the conversation going on through it overheard, or its 

 operation interfered with. Sir William Preece has published results 

 which go to show that it is possible to pick up at a distance on 

 another circuit, the conversation which may be passing through a 

 telephone or telegraph wire. 



Up to the commencement of 1902, the only receivers that could 

 be practically employed for the purposes of wireless telegraphy were 

 based on what may be called the coherer principle — that is, the 

 detector, the principle of which is based on the discoveries and 

 observations made by S. A. Yarley, Professor Hughes, Calsecchi Onesti, 

 and Professor Branly. 



Early in that year the author was fortunate enough to succeed in 

 constructing a practical receiver of electric waves, based on a principle 

 different from that of the coherer. Speaking from the experience 



