Manawatu Herald SATURDAY, OCTOBER 4, 1919. GUIDING SHIPS BY SOUND.

Manawatu Herald, Volume XLI, Issue 2037, 4 October 1919, Page 2

Manawatu Herald SATURDAY, OCTOBER 4, 1919. GUIDING SHIPS BY SOUND.

A NEW method of determining the position of a vessel ul sea by means of sounds originating from it is de-

scribed in the journal, Engineering-, by Professor J. C. McLennan. By the use of the hydrophone, the explosions duo to charges of 2lb. of T.N.T. have been recorded a I 14 miles, those-of 300 lb. depth charges have been recorded up to 200 miles, and it is probable that with charges of moderate amount, explosions occurring as far array as 4300 miles can be readily recorded. Based on these results a system of sound ranging under water was developed. 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- hydro phonos were placed along a line at right angles to the base line, one Jive miles out and the other twcie that distance. Cables were laid from the hydrophones to a recording instrument situated in a shore station. Four of these stations were installed at different places along the east coast of the British Isles, and other stations are now in progress of installation. With such sound-ranging systems j Be shock of distant explosions occurring linger water affects the various -Hydrophones. in turn, ami as lime intervals can be read to two or three thousandths of a second with the apparatus now in use, it is possible to measure with accuracy the intervals between the times of arrival of a sound wave at the different hydrophones. With (he measurements of these time intervals it is a. simple matter to deduce the position of the point at which the explosion setting up. the wave is located/ Up to fifty miles the location of an explosion under water can be determined to within a few hundred yards by a single station, but for accuracy the co-operation of two stations would he necessary to locate explosions at greater distances. Within operable ranges a ship can be given its position by sound ranging more accurately than by directional wireless or by any other known method. Explosions of mines or torpedoes at any point in the North Sea can easily be located by stations .situated in Great during the bombardment of the Belgian coast it was a common thing for a monitor to proceed in a fog to a position some miles from the coast and by dropping depth charges have

its 'position curalely determined from .stations on the coast of Eng-' land. So accurately was this done that it was found when the monitor’s guns were trained in selected directions several miles inland could'be hit with regularity and with a minimum expenditure of ammunition, .