SUBMARINE SIGNALING BLAKE. 205 



advance was made. Water has many advantages over air for this 

 purpose. 



1. In the first place, it is free from the dangerous zones of silence 

 which occur when the signals are produced in air. 



2. In the second place, the absorption of the sound is much less 

 in water, and consequently the signal is not only absolutely reliable 

 but is transmitted to a distance many times greater than when it is 

 transmitted through air. 



3. The sound is not carried away by the wind in stormy weather, 

 as is the case with the siren. 



4. It is not affected by atmospheric disturbances, as is the case of 

 wireless. 



5. It permits of the accurate determination of the direction from 

 which the sound is proceeding, which is not the case with either the 

 air siren or wireless telegraphy. 



Some recent instances where ships have signaled by wireless that 

 they were in distress but have had to remain without assistance for 

 many hours, and in one instance for more than a day, because their 

 location could not be determined by the vessels coming to their aid, 

 will be familiar to everyone. 



All these advantages indicated clearly years ago the advisabilitv 

 of developing apparatus for signaling by means of sound waves 

 transmitted through the water itself. 



But it is one thing to conceive the idea and another thing to 

 develop a practical system; and it may be of interest to know that 

 up to the present time the sum of a million dollars has been invested 

 in developing submarine signaling, so far without monetary return. 



The first method which was employed for producing the sound 

 was through the striking of a bell, and the method of receipt of the 

 signals w^as by means of a microphone attached to the skin of the 

 ship. Neither the original bell nor the original microphone attach- 

 ment was satisfactory. 



It would b© impossible in the space permitted to discuss even briefly 

 the innumerable experiments made with different sizes of bell, with 

 different materials for the bell, with different methods of producing 

 the blow, the precautions taken to eliminate electrolytic action, with 

 different types of microphone, with different methods of mounting 

 the microphone on the side of the ship, with the experiments made 

 to minimize water and other noises. It will be sufficient to say that 

 finally the work of Mundy, Wood, Fay, Williams, and others resulted 

 in a completely practical system. 



The submarine bell in use on the lightships is actuated by com- 

 pressed air stored in a reservoir. The actuating wheel has projections 

 mounted on it so that when the wheel revolves a number of strokes 



