118 SUBMARINE SIGNALING AND A PROPOSED 



who have never heard a submarine bell would, unless instructed, never identify this 

 dull, instantaneous click for the bell sound that experience in air sounds wouldnat- 

 urally lead them to expect. 



The knowledge of the efficiency of water as a sound medium had existed for 

 a very long time before any successful application was made for navigational pur- 

 poses. The inherent difficulties of receiving the sound on board of a vessel under 

 way due to interference from ship noises, and of transmitting submarine signals 

 from vessels under way, prevented its practical use. Over fifty years had elapsed 

 from the experiments of Colladon and Sturm to the date when the first patent is- 

 sued on the application of the principle of water signaling. The discovery of the 

 telephone had not improbably turned attention to its utilization for this purpose. 

 A patent was issued to Mr. Henry Edmunds in 1878. He proposed the use of a 

 bell or gong for sending, and a telephone for receiving. Among the numerous in- 

 ventors who have since applied themselves to the subject is the name of Thomas 

 A. Edison. 



The development of submarine signaling, which finally resulted in successful 

 commercial application, began in 1898. Mr. A. J. Mundy, of Boston, collaborating 

 with Professor Elisha Gray, carried on continuous experiments up to the death of 

 the latter in 1901, at which time after three years, although much data had been 

 obtained, the problem was still unsolved. 



No sending apparatus had been discovered which could be installed in a mov- 

 ing vessel, and no receiver had been developed which was not rendered useless with 

 a ship under way on account of the noises of the ship and water rushes. The com- 

 plete problem demands an apparatus for sending from a ship under way, and receiv- 

 ing the message on a ship under way. A solution of the latter was discovered by 

 Mr. Mundy. He found that a sound wave traveling through water would pass 

 through a steel plate immersed in the water without serious diminution, and that 

 therefore the sound waves could be heard within a compartment of a vessel if filled 

 with water. A microphone immersed in water intercepted the distant sound sig- 

 nal, and at the same time was not sufficiently afiFected by the water rushes and for- 

 eign noises to prevent the reception of the distant sound wave traveling from the 

 bell. By designing receiving tanks filled with water in which the microphone was 

 immersed, it was finally found that a tank 18 inches deep and 16 inches square was 

 sufficiently large for the purpose, and the present commercial type is of the above 

 size shown installed in Fig. i, Plate 45. 



The submarine bell designed after many experiments is that shown in Fig. 2, 

 Plate 45. The marked difference in cross-section with a bell to be sounded in air 

 is notable. Vibrations of 1,215 per second were adopted for efficient range and 

 audibility. . 



The development of a satisfactory signal system, at least for naval purposes, 

 requires that the signals be sent equally well in all directions and that they be re- 

 ceived with equal facility from all directions. 



The ideal intensity curve of a sending system and the audibility curve of a re- 



