ADVANCES IN SIGNALLING 245 



they faintly whisper the secrets of all the radio communications 

 of the world. 



Increase of Radio Precision and Range. It has been esti- 

 mated that at least in two directions, the war advanced applied 

 science more in four years than perhaps might have been accom- 

 plished in twenty or thirty years of peace; namely (i) in air- 

 ships or airshipping, and (2) in radio communication. The 

 great number of radio messages, passing simultaneously through 

 the air, forced the necessity of learning to tune sharply, in order 

 to effect precise and accurate inter-communication in the Allied 

 armies. Moreover, the ranges of radio signalling by telephone 

 and by telegraph were greatly increased. In regard to radio- 

 telegraphy, the range was increased until it actually encircles 

 the globe. It was found during the war that radio signals 

 emitted at Carnarvon, in Wales, were detected and read suc- 

 cessfully at Sydney, New South Wales, Australia. Any ter- 

 restial globe will show that the British Wales and New South 

 Wales are nearly diametrically opposite. We may, therefore, 

 expect that, in the future, radio telegraphy will expand not 

 merely across oceans, but around the world in all directions 

 simultaneously. 



The time that it takes an electromagnetic wave to run around 

 the globe, from the radio station of emission to an antipodean 

 radio station of reception, has not yet been actually measured ; 

 although the time of transmission of radio signals has been 

 determined photographically, between Washington, D. C, and 

 Paris, France, an overseas distance of 6175 kilometers, as 0.021 

 second. The wave travels very nearly as fast as light in vacuo; 

 i.e., 300,000 kilometers per second. Since the distance from 

 pole to pole is 20,000 kilometers, the time for any wave to 

 travel to an antipodean station should not much exceed one- 

 fifteenth of a second. Consequently, all parts of our world 

 have shrunk, during the war, to something less than one-tenth 

 of a second of utmost separation or remoteness. How hope- 

 less, in the future, must such a world be without a league, nay 



