xi ACROSS THE BORDER 297 



bility of telegraphy without wires, posts, cables, or any of our 

 present costly appliances. Granted a few reasonable postulates, 

 the whole thing comes well within the realms of possible fulfil- 

 ment. Sir William Grookes. 



The receiver used by Hertz was not suitable for tele- 

 graphic work, but a more practicable form was soon 

 found, and was used in a lecture delivered by Sir Oliver 

 Lodge before the Royal Institution in 1894, when the 

 statement was made that the apparatus would respond 

 to signals at a distance of half a mile. Two years later, 

 Mr. Marconi filed a provisional specification of apparatus 

 for signalling by means of electric waves. 



Mr. Marconi not only saw that the laboratory experi- 

 ments of Hertz might be put to practical use, but also 

 proceeded to adapt them to a system of telegraphy 

 through the ether. As the radiator of electric waves 

 he introduced a long vertical wire, broken by a spark 

 gap, so that the pulses could surge up the wire and down 

 into the earth, sending waves out into the ether in all 

 directions as they did so. He constructed a more 

 sensitive and trustworthy instrument to detect the 

 waves, and ascertained what energy was required to 

 make it possible to signal over any distance. To his 

 knowledge, confidence and daring must be ascribed 

 the commercial development of wireless telegraphy. 

 By experiments carried out on Salisbury Plain, he first 

 succeeded in transmitting messages over a distance of 

 two miles ; in 1898 he sent messages from Poole to Alum 

 Bay, Isle of Wight a distance of eighteen miles ; and 

 by 1910 he was able to produce electric waves so powerful 

 that their influence could be detected, and signals read, 

 at a distance of six thousand miles. This remarkable 

 performance,which suggests marvellous possibilities for 

 the future, was achieved as the direct outcome of the 



