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Telegraphy

sound, water, bell, receiver and ship

TELEGRAPHY, Submarine Sound, a system of communication between steamships at sea by sound telegraph through water. In 1901 A. J. Mundy tested. an experimental boat in Boston Harbor, based on experiments in the conductivity of sound through liquids by Prof. Elisha Gray. Experiments by. B. Millet J proved remarkably successful Signals were exchanged between lightship bell and a ship seven miles distant at sea. Sound travels faster through water or liquids than air, and this is taken advantage of in a practical way. In the ship at sea are two sound receivers, one upon each side in the hold, located approxi mately 20 feet below the surface of the water. The lightship has the sounding bell hung through a well in the centre of the ship, about 25 feet below the bottom. It also has a receiv ing apparatus. Near the lighthouse on shore is a buoy from which depends a bell, with a pipe leading to the shore to a compressed-air reservoir in the lighthouse. The bell is sus pended by a main chain, while a second operat ing chain is attached at its lower end to the bell crank of the hammer, and the upper end to a pneumatic piston, which is operated by com pressed air either from the anchored lightship or the lighthouse, as the case may be, or it may be operated by a direct upward pull by manual power if desired. It has been ascertained that the receiver for collecting the sound vibrations need not be located on the outside of the vessel, but operates as well when clamped on the inside against the inner surface of the outer hull, especially in iron ships. The sound

vibration from the bell passing through the water is communicated to the side of the ship's hull, and that•in turn to the liquid or water in the receiver; which is a cup-shaped metal cyl inder having the open end clamped against the side of the hull. Inserted in the top of the receiver is an electric transmitter, something on the order of a telephone transmitter, from which wires are run to the pilot-house of the ship. As the sound travels through the water in every direction from its source, it is found that the impulse will be stronger and louder on the side of the ship nearest to the source. By this means the direction of the sounding bell is ascertained, for by listening to the telephone receiver attached to the starboard side water receiver, and then switching over to the port side and listening to that telephone receiver, the ear detects at once which is the louder sound of the two. This was determined experimen tally by turning the ship around in a large circle. In foggy weather, signals of this kind are readily heard, regardless of which way the wind is 'blowing. The usefulness of the system in safeguarding ships against collisions at sea at night or in a fog is evident. Simon Lake, in ventor of the Lake submarine'boat, has experi mented with under-water telephony with con siderable success and applied it to his undersea craft