Radio broadcast .. (1922-30)

Making Life Safe at Sea 469 making it attractive for owners to provide ships with safety devices which are practical. FOG — THE GREATEST MENACE WE HAVE made great progress in marine engineering, and storms no longer hold the danger they formerly did. Derelicts are systematically sought and removed. Icebergs are located and their positions broadcasted to mariners by radio. Careful charting of the Seven Seas, accomplished at great cost by the various countries, and the establishment of lights on dangerous shoals and promontories have stripped the sea of much of its former risk, but one great hazard remains — the one mariners fear most — fog! Millions have been spent for fog-horns and other sound-producing devices but they are all subject to error, due to variations in atmospheric density which prevent the sound waves from traveling in a given direction. Sound waves may be refracted from side to side or up and down, resulting in certain areas where the sound is not heard at all. VESSELS LED TO DISASTER BY REFLECTED SIGNALS IN a paper presented at the 2Qth Annual Convention of the American Institute of Electrical Engineers in Boston, June 27, 1912, Mr. H. J. W. Fay pointed out that from 1893 to 1902 between 900 and 1000 vessels were wrecked by aberrations of sound or by being drawn on a false course by echo. The approximate loss in property amounted to $57,500,000 and no less than 530 human beings were sacrificed. These statistics became an appeal for the mariner, and encouraged inventors to renewed efforts which were at last realized in a successful system of submarine signaling. SUBMARINE SIGNALING! ITS ORIGIN THE system which has been perfected for sea warnings is based upon the fact that sound travels through water without the distortion, reflection and refraction which obtains where air is the carrying medium. Sound under water has another advantage: it travels faster than in air. It is impossible to determine with accuracy the originator of this form of communication, and, were the truth known, it is quite likely that primitive man made use of some form of under water signaling, however crude his instruments may have been. It is said that the natives of Ceylon used this knowledge many years ago to signal each other when at sea in their fishing boats. They used an earthen "chatty" which was submerged and struck with some hard object. A sharp percussive clink was thus produced which could be heard by placing the ear against the bottom of a boat many miles distant. In 1826 we find that two scientists, Messrs. Colladon and Sturm, sought to measure the velocity of sound in water. They struck a submerged bell with a hammer and listened for the sound by submerging one end of a common ear trumpet and holding the other end to the ear. It is quite likely that they were aware of the experiments made in 1767 by a Scotch scientist who managed to hear a large hand bell at a distance of 1200 feet by the simple expedient of submerging his head. It would seem, therefore, that there is nothing very new about submarine signaling — at least in theory. It was known long before anyone thought of securing patents on it or putting it to any practical use. EARLY DEVELOPMENT OF UNDERSEA SIGNALING THE first published record of any attempt to apply the principles of under-water signaling to some useful purpose is found in an English patent issued in 1878 to Henry Edmunds. This patent describes a system for ringing* a submarine bell by electricity: for attaching a bell to a buoy and taking advantage of the wave motion to supply power for operating the bell, as well as the suggestion that sounds could be created under water by submerging and energizing an ordinary telephone receiver. The underlying principles of this patent are quite like those in use to-day, though they have been greatly refined. For a receiver, Mr. Edmunds suggested the use of an oar with its blade under water and