HAYES-DETECTION OF SUBMARINES. 



receiver when attached to the inside of the skin of a boat well below 

 the water line is fairly sensitive to submarine sounds. The ordinary 

 stethoscope is an example of the geophone. 



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Plate I. Types of submarine receivers. 



The Microphone consists of two polished graphite plates placed 

 parallel to one another and separated about %6 of an inch. The 



