GUIDING SHIPS BY SOUND.

Taihape Daily Times, 3 October 1919, Page 3

GUIDING SHIPS BY SOUND.

_._U._..__ A new method of determining the position of a" {vessel at ‘sea by means of sounds originating from it is described in Thc J'oul'llal, Engineel'ing, !by Professor J. C. McLennan. By the use of the ‘hydro-phone, the explosions lane to charges of 21b of T.N.T. have ‘been recorded at 14 miles, those of l 3001 b depth Cllal’gos have been recorded {up to 200 miles, and it is probable that with charges of moderate amount ithc explosions occurring as far awayras 1500 milcs'ca.n be readily recorded. ißased on these results, -a- system of sound ranging under water was de- ! veloped. Four hydrophones were laid out five miles apart along a base line in deep water a mile or two from the shore, and in addition, two pilot hydrophones were placed along 3 line at right angle to the base line, one live miles out and the other twice that distance. Cables were laid from the hydroph-ones to lav recording instrument situated in a shore station. Four of these stations were istalled at different places’ along the east coast of the British Isles, and other stations -are now in progress ‘of installation. \Nit.h such sound-ranging systems the shock of distant explosions occurring under water affects the various hydrophones in turn, and as time I.nterva.ls can be read to two or three thous-andths of a second with the apparatus now in use, it is possible: to’ measure with accuracy the intervals betwen ithe times of arrival of a sound wave at the difierent hydrophones. With the measurements of these time intervn-ls it is a. simple matter to deduce the position of the point at which the explosion. setting iup the wave is located. Up to fifty’ ’miles ‘the location of an explosion under water can be determined to within :1 few hundred yards by a. single station, but for accuracy the co-operation of two stations would be necessary ‘to locate explosions at greater distances. Withi‘n operables range a ship can be -given its position by sound ranging more -accurately than by directional wireless or by any other known method. Explosion -of mines or torpedoes at any point in the North Sea can easily be located by stations situ"ated in Great Britain. In the war, during the bombardment of the -Belgian coast it was a common thing for '3, monitor to proceed in a. fog to a position some miles from the ‘ coast and by dropping depth charges: have its position accurately determined from stations on the coast of England. S 0 accurately was this done that it was found when the monitor’s guns were trained in selected direce tiong objectives several miles inland could be hit with regularity and with

:1 milimum expenditure of’ ammunition