In the three days beginning March 10, 1915, eight ships were made victims of German submarines in the waters about the British Isles. Most novel was the experience of a crowd gathered on the shore of one of the Scilly Islands on March 12, 1915, when two of these eight ships, the _Indian City_ and the _Headlands_, were torpedoed. At about eight in the morning the islanders on St. Mary's Island saw a German submarine overtake the former and sink her. The German vessel then remained in the adjacent waters to watch for the approach of another victim, while two patrol boats near by put out and opened fire on her. The crowd saw the enemies exchange shots at a distance of ten miles off shore. But neither side put in any effective shots, and the combat ended when the submarine dived and retired. The steamship _Headlands_ was then sighted by the commander of the submarine and he immediately started to pursue her. The steamship steered a zigzag course, but the submarine got in a position to launch a torpedo, and at about half past ten in the morning the crowd on the shore saw steam escaping from her in large quantities. Some time after they saw a large volume of black smoke and debris fly upward and they knew that another torpedo had found its mark. She then settled, her crew and the men from the _Indian City_ reaching St. Mary's in small boats. To keep British harbors free from the German submarines the British admiralty had to set their engineers to work to devise some method of trapping the underwater craft automatically, for there seemed to be no sort of patrol which they could not elude. Steel traps, not unlike the gill nets used by fishermen, were finally hit upon as the best thing to use against the submarines, and by March 13, 1915, a number of these were installed at entrances to some of the British harbors. They were made of malleable iron frames, ten feet square, used in sets of threes, so arranged that they might hold a submarine by the sides and have the third of the set buckle against its bottom. They were suspended by buoys about thirty feet below the surface of the water. When a submarine entered one of these it was held fast, for the frame which came up from the bottom caught the propeller and made it impossible for the submarine to work itself loose. The disadvantage to the submarine was that, while traveling under water, it traveled "blind"; the periscopes in use were good only for observation when the top of them were above water; when submerged the commander of a submarine had to steer by chart. By the end of March, 1915, a dozen submarines had been caught in nets of this kind.