HERTZIAN WAVE WIRELESS TELEGRAPHY. 57 



and shore stations in proximity, equipped with Marconi apparatus of 

 a suitable type. 



These experiments were carried out on the eighteenth of March last, 

 at Poldhu, in Cornwall, and a program was arranged by the author of 

 the following kind. Close to the Poldhu station is an isolated mast, 

 which was equipped by Mr. Marconi with a Hertzian wave apparatus, 

 similar to that he places on ships. Six miles from Poldhu is the Lizard 

 receiving station, with which ships proceeding up or down the English 

 Channel communicate. It was arranged that a series of secret mes- 

 sages, some of them in cipher, should be delivered simultaneously at 

 certain known times, both to the power station at Poldhu and to the 

 small adjacent ship station; and it was arranged that these messages 

 should be sent off simultaneously, the operators being kept in ignorance 

 up to the moment of sending as to the nature of the messages. At the 

 Lizard, Mr. Marconi connected two of his receiving instruments to the 

 aerial, one of them tuned to the waves proceeding from the power sta- 

 tion at Poldhu, and the other to those proceeding from the small 

 ship station. At the appointed time, these two sets of messages were 

 received simultaneously in the presence of the author, each message 

 being printed down independently on its own receiver; and Mr. Mar- 

 coni read off and interpreted all these messages perfectly correctly, not 

 having known before what was the message that was about to be sent. 

 In addition to this, precautions were taken to prove that the power 

 station at Poldhu was really emitting waves sufficiently powerful to 

 cross the Atlantic and not being made to sing small for the occasion. 

 To assist in proving this, the messages sent out from the power station 

 were also received at a station at Poole, two hundred miles away, and 

 the assistant there was instructed to telegraph back these messages by 

 wire as soon as he received them. These messages came back perfectly 

 correctly, thus demonstrating that the power station was sending out 

 power waves. The whole program was carried out with the greatest 

 care to avoid any mistakes on the part of the assistants, and provided 

 an absolute demonstration of the truth of Mr. Marconi's assertion that 

 the waves from one of his power stations, such as Poldhu, do not ia 

 the least degree interfere with the transmission and reception of mes- 

 sages between ship and shore, effected by means of certain forms of 

 Marconi apparatus for producing and detecting waves of a different 

 wave length.* This complete independence of transmission, however, is 

 entirely due to the employment of a receiving circuit of a certain type 

 in Mr. Marconi's receivers. It does not at all follow that receiving 

 circuit of any kind, even a Marconi receiver not especially arranged, 

 set up in proximity to a power station would not be affected. This, 



* A fuller account of these experiments was given by the author in a 

 letter to the London Times published on April 14, 1903. 



