The Imperial Maritime Castoms have decided to instal submarine signalling apparatus on the lightships Kintoan and Tongsha and at the Bell Baoy, and for experimental purposes subman receiving apparatus on two of their raisers. Mesars Wheelock & Ca, the agents for China of the Submarine Bignal Ca., hope to have the trial apparatus for the Customs here during the month of April and a short time afterwards it will be available for use.
Submarine signalling has been adopted largely in England, Germany and America with great success as aid to n, and if it is installed on the Chioa coast and the various shipping companies fit their vessels with ig This system of signalling by sound under water enables seamen to locate the position of their ships and to find the beatings of boys, lighthouses, and lightships when the vessel can enter a harbour safely in fog, and need not be delayed because her captain cannot see lights or hear other fog-signals. Ships equipped with the signalling and receiving apparatus can also locate each other in thick weather, and avoid collisions, By simple means any two vessels so eqnipped can communicate with each other, or with a shore station, by code signals. A fishing-schooner can find her dories in a fog, a battleship can communicate with her deployed submarine boats, or two submarine boats can signal each other.
Briefly the system is as follows From a lightship, lighthouse or buoy, as the cage may ibe, a loll is rang surface of the ster. ery one knows, is good conductor of sound, with the result that vessels equipped with receiving apparatus can hear the sound of bells rung under the surface of the water for long distances, The ree iting spparatae on a ship consiste of a tank placed against the skin of the ship below the water line and well forward, just about at the blaff suspended inside this tank s microphone connected by means of a telephone with the bridge. With two of thes" tanks, tone en each bow it is possible for the officer in charge on the bridge to hear the sounds of the bell at us great distance as fifteen or sixteen miles, and since there is a separate reviver to each the direction of th seand by swinging ip, within a quarter of a point of the compass.
The reasons why submarine sound-signals are preferred to othertypesof fog-signals sre easy to understand. Before this method of signalling under water, ras
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