108 RECENT DEVELOPMENTS IN SUBMARINE SIGNALING. 



ascertain whether sound in water could be used as an aid to navigation. Very soon 

 after this, similar attempts were made in England and then, although the experi- 

 ments, especially those of Professor Blake, were exceedingly promising, the whole 

 matter was allowed to drop. 



In recalling the history of the art it is well to remember, therefore, that as early 

 as 1883 Professor Blake, an American, demonstrated that sound in water could be 

 heard at long distances by ships provided with receiving apparatus. He also con- 

 templated providing ships with some kind of a sound producer. No attempts, how- 

 ever, were made to ascertain the direction from which the sound proceeded, or to 

 work out a practical apparatus. 



Even before this, in 1826, Messrs. CoUadon and Sturn, on Lake Geneva, had 

 heard a heavy bell rung under water at a distance of ten miles. This was long 

 before the invention of microphones, and their receiving apparatus was much like 

 a cornucopia ear trumpet with a rubber diaphragm stretched across the larger end 

 in order to prevent water from entering it. 



Ten years after Professor Blake had finished his experiments, and the momen- 

 tary interest in his work had died out, Mr. A. J. Mundy, of Boston, having no 

 knowledo"e whatever that anyone had ever made any attempts to use sound in water 

 for this purpose, conceived the idea and undertook experiments of his own, aided 

 by Prof. Elisha Gray, the eminent inventor. Mr. Mundy took his hint from the fact 

 that as a boy, when in bathing with his head under water, he could hear 

 stones cracked together under water at a very long distance. His earlier experi- 

 ments, like those of Neale and Smallpage in England fifteen years before, con- 

 templated a microphone receiver such as is used in the telephone as a transmitter, 

 attached to the ship. Experiments proved that the noises made by the machinery 

 on board the ship created so much sound of their own as to make it impossible to 

 hear anything else if the receivers were fastened to the wall of the ship. In an 

 effort to overcome this, Mr. Mundy tried hanging a microphone in a tank filled 

 with water which was attached to the inner skin of a vessel under water. It was 

 found at once that the skin of the ship did not interfere in the least with the pas- 

 sage of sound from the sea outside into the tank inside, and other ship's sounds were 

 laro-ely excluded. The microphone located in the tank picked up the sound and 

 transmitted it by the usual method to any point where it was desired to receive it. 

 From this moment the invention went on apace. Various sizes of tanks were tried, 

 but those finally adopted were about the size of half a beer barrel and were con- 

 structed so that one end of them was formed by the skin of the ship. After a 

 great many experiments on the sea in ships of all sizes and in all weathers, it was 

 found that in order to obtain direction it was necessary to have a tank on each 

 side of the ship somewhat forward of the bluff of the bow, and by comparing the 

 intensity of the bell sound on one side of the ship with that on the other the direc- 

 tion was readily ascertained. 



Mr. Mundy's sudden illness placed this problem of finding direction on my 

 shoulders, and in solving it I used the steamships of the Metropolitan Line which 



