44 THE NEW WORLD OF SCIENCE 



phase difference. The angular accuracy of setting is thus in- 

 creased twelve fold. 



Two methods of applying the principle were used in the 

 war. The one consisted in rotating the whole receiving system, 

 one side of which was connected with a rubber tube to one ear, 

 the other side in the same way to the other ear, until the ob- 

 server had the sensation of feeling the sound pass from one 

 ear to the other. At this instant he knew that the source was 

 directly ahead of the line connecting the two receivers, or else 

 directly behind this line, the distinction between the two posi- 

 tions being obtainable from the relation between the direction 

 of the motion of the head and the direction in which the sound 

 seemed to pass from one ear to the other. The second method, 

 the one used with the submarine detector discussed above, con- 

 sisted in keeping the receiving system fixed in space and chang- 

 ing the length of the sound path from each receiver to the ear 

 by means of a so-called rotating commutator until the sound 

 seemed to be passing from one ear to the other. The reading 

 of the dial on the compensator then gave the direction of the 

 source. 



This principle proved so effective in locating enemy mining 

 and tunneling operations that according to official despatches 

 received by the Research Information Service both sides gave 

 up such operations practically entirely a year or more before 

 the close of the war. It was equally effective in anti-submarine 

 warfare, a very simple form of binaural detector having been 

 put out in large numbers by the General Electric Company, 

 in addition to the more elaborate and more effective devices 

 heretofore considered. The principle was less effective in its 

 application to anti-aircraft work though even here it served 

 a very useful purpose. 



The third physical principle which was of immense use in 

 the war was the principle of amplification. This extraordinary 

 application of scientific investigations of the past two decades 

 in the field of electron discharges had been reduced to practice 

 in the telephone industry in 1914 when transcontinental wire 



