CHASING U-BOATS
DETECTION BY SOUND. LECTURE BY NAVAL MAN. AUCKLAND, August 1. A glimpse oi the working of the renmrkable complete organisation for checking the German U-boat menace during the Great War was given last evening by Lieutenant-Commander U. I'. Aisbet, D.S.C., R.N.R., in a lectureentitled “Chasing the Hidden Enemy by Sound,” delivered under the auspices of the Victoria League. The high degree of accuracy attained in dot rmining the position of U-boats by means of the “fish” hydrophone, an instrument towed behind British naval vessels for picking up the sound ot submarine engines, was detailed by Lieutenant-Commander Nisbet. Ships of tile trawler type were spi’Ciall built as hydrophone ships, and they worked in groups, or divisions, ot three. Their function was to detect the presence of the .submarine and signal its position to the destroyer, or similar fast vessel, that worked in conjunction with each hydrophone division. The destroyer’s task was then to steam quickly to the point indicated and drop a series of depth charges.
Trawler’s Exciting History. “I was in command of the loth Division,” said Lieuten'ant-Gommander Nisbet, “and you will be interested to know that my ship was the trawler James Cosgrove, now so well known to Aucklanders. Jt is a coincidence' that I should have followed her to New Zealand. It can be said that she lias a history as exciting as that of almost any other trawler that saw war service.” On one occasion his division delected a submarine about sixty miles north of Iceland. For four days and nights they followed it, but owing to its superior speed it kept beyond their reach. The submarine commander knew he was being followed, for submarines could always detect the presence of surface craft by the noise of their propellers. He dodged and turned, and the pursuing ships did the same, until fiiially they lost all sense of their position, being so engrosed in attending to their hydrophones.
Chase Interrupted. Early one morning during the chase tile submarine was sighted just as it was breaking the surface, but it quickly dived. Depth charges were dropped, but without effect upon the U-boat. The explosives, however, placed their hydrophones out of commission and valuable time was lost in hauling them in and changing them. With new d■-tec-tors fitted they picked up the sound of the U-boat’s engines again and the chase was resumed. Then, to the immense disappointment of all, when the dawn of the fifth day broke, they found themselves alongside the Faroe Islands and saw the submarine proceeding boldly on the surface, immune from their attack, since it was in Danish and therefore neutral waters. “To realise the significance of this,” said Lieut.-Commander Nisbet, “you must' remember that the submarine, like us, had been twisting and turning for four days and nights, here, and there and all over the place. YVe, on the surface, were lost. But he. under the surface, had managed to reach the islands. I must pay a tribute to his wonderful navigation.”
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Hokitika Guardian, 5 August 1931, Page 8
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500CHASING U-BOATS Hokitika Guardian, 5 August 1931, Page 8
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