Submarine Appliances And Their Uses
Deep Sea Diving, &c., &c.

SUBMARINE SIGNALLING APPARATUS. When it is remembered that sound travels more than four times as fast in water as in air* and that m water it 1S not subject to the same possible obstructions and variations as it is in air, it will be readily understood how much more effective and reliable is submarine than aerial signalling under certain conditions. 1 YrES OF SUBMARINE SIGNALS. Reproduced by courtesy of The Submarine Signal Co. General View of the Submarine Sound Signalling System, showing its different applications. The conception of the Submarine Fog Signalling Bell is probably due to the scientist, Colladon, who, m his experiments on Lake Geneva, in 1826, had a bell weighing- iqo lbs sus pended Sft. under water from the side of a boat and struck by a hammer attached to the end of a lever Stationed m another boat, he listened for the bell sounds propagated beneath the surface; which were conveyed from the water by a cylindrical tube of tin some oft. long- and Gin. m diameter. One end of this tube terminated in an orifice for insertion in the ear, and the other was spread out somewhat in the form of a spoon, with its orifice closed by an elliptical plate of tin about two square feet in area. By attaching a suitable weight to the lower end of the tube it was easily retained in a vertical position, with about four-fifths of its length submerged, its plate being turned toward the boat carrying the bell. With this simple apparatus, Colladon was able to hear, with perfect distinctness, the blows of the hammer on the bell across the widest part of Lake Geneva, when the calculated distance be- tween the two boats was not less than eight miles. Small progress, however, seems to have been made in the ait of under water signalling until the year 1900, when Mr. A T Mundy an American, turned his attention to the subject, and with the aid of expert assistants sue’ ceeded, after innumerable experiments, in producing a system which macle it possible to strike a note on a bell under water at regular intervals, and to enable the navigator of a ship travelling at high speed to receive the sounds twelve to fifteen miles from their source without leaving his wheel-house. Submarine Signalling Apparatus consists of two main parts: (1) the SENDING AP- PARATUS, which for all practical purposes, is confined to BELLS; and (2) the RFCFTV ING APPARATUS. k In air the velocity is 1,100 ft. per second, and in water 4,700ft. per second, N)