1897.] 



on Signalling through Space ivithout Wires. 



475 



Brighton. How this was done was never known, for his secret died 

 shortly afterwards with him. It certainly was not by means of 

 Marconi's relay. 



I he distance to which signals have been sent is remarkable. On 

 Salisbury Plain Mr. Marconi covered a distance of four miles. In 

 the Bristol Channel this has been extended to over eight miles, and 

 we have by no means reached the limit. It is interesting to read the 

 surmises of others. Half a mile was the wildest dream.* 



It is easy to transmit many messages in any direction at the same 

 time. It is only necessary to tune the transmitters and receivers to 

 the same frequency or " note." I could show this here, but we are 



Fig. 5. — Diagram of Marconi connections when using pole or kite. 



bothered by reflection from the walls. This does not happen in open 

 space. Tuning is very easy. It is simply necessary to vary the 

 capacity of the receiver, and this is done by increasing the length of 

 the wings W in Fig. 2. The proper length is found experimentally 

 close to the transmitter. It is practically impossible to do so far away. 



* "Unfortunately at present we cannot detect the electromagnetic waves 

 more than 100 feet from their source." — Trowbridge, 1897, ' What is Elec- 

 tricdry,' page 256. 



"I mention 40 yards because that was one of the first out of door experi- 

 ments, but I should think that something more like half a mile was nearer the 

 limit of sensibility. However, this is a rash statement not at present verified." — 

 Oliver Lodge, 1894, ' The Work of Hertz,' page 18. 



