SUBMARINE SOUND-SIGNALLING.

Timaru Herald, Volume XIIC, Issue 13941, 29 June 1909, Page 4

SUBMARINE SOUND-SIGNALLING.

The " Gazette "of the 24 th inst. contains -.'a. five-column article extracted by the Minister .of. Marino from the June "Pilot of the North Pacific Ocean," on Submarine 'Sound-Signal-ling. In this we find a hint that tlio system might occasionally be mad« use of at Timaru with advantage. ■ Now and then-a Union Company's steamer is "held up" outside, unable to make her way into the harbour on account of a thick fog. Her horn is kept going to advertise' her difficulty; whistles and hooters are sounded on shore to indicate the whereabouts of •

the port;' and sometimes a boat is sent out with a aboard to serve as a guide. And after all, the attempts to guide the navigation of the steamer may fail, owing to the difficulty of accurately fixing - the direction ■ whence a'-'sound- comes. The submarine sound-signal is made under water by means of: a submerged bell, and the signals can be heard very nnicn further, • their direction can be ascertained much more certainly, than sound waves .in. air. The article referred to states that" a common range of hearing is three to five miles, while instances are recorded of the signals being picked up at 12 miles,-and even as much as 27- miles. These submarine bell signals are used on nearly fifty light-ships arid' at coast stations in the United States and Canada, and about 30 off the coasts of different European countries, on 'light shr t .-s chiefly. In order to make, the arrangement perfect, it is necessary.to have microphones' fixed.inside the .travelling ship, one on each"side, of the bow, :«s low down as possible, with electric connection to a telephone on deck. This does not appear to be absolutely necessary for picking up strong sounds from a short 'distance, as they can be heard by placing the ear close to the plates of the vessel; or more conveniently by means of a weighted tube with an expansion covered by a flat plate at the lower- end. By turning this about, the direction of the sound can be nearly ascertained. The hint for Ttinnru is contained in the final paragraph of the paper, and it is that ) y placing a sounder in a suitable position within a harbour,' so that the sound waves can issue through the entrance, and travelling outwards will serve to indicate to a vesel picking up the signals the direction of the harbour. lc does not appear to be. necessary th-t the sounder should be a bell. A suspended steel fail would probably answer as well, if not better. It has boon proposed to construct a steam hooter or whistle to sound imdcr water. And, if a simple unmeasured noise of far-reaching quality were all that is required, the turning of a steam pipe deep into the water should furnish by the. concussions of the water from the condensing steam an abundance of powerful vibrations in the water. On the other hand, Colladon's receiver was simple enough to be made by any tinsmith, and be stowed anywhere, on deck when not in use.