The words were hardly out of his mouth when a dull, rasping sound announced the unpleasant fact that the submarine was scraping over the shingly bottom. To reverse the motors to back off the ledge would mean instant detection. Ten seconds of breathless suspense followed. During that time the submerged craft was still forging ahead, till without losing way she slid into deep water. She was safely within the secret haven. "By Jove, I've got her! There she is!" exclaimed the Lieutenant-Commander. It was now dawn, with sufficient light to discern the outlines of the _unterseeboot_. She had warped out from her inshore berth, and was now lying at anchor in about the same position as when Dick had first discovered her. Her deck was showing about two feet above the surface. Alongside was the Berthon boat with two men on board. On the submarine the only signs of life were a couple of seamen patrolling the limited extent of deck. "Stand by--both tubes," ordered the Lieutenant-Commander. He was determined to take no risks of a miss. The twenty-one-inch gleaming steel cylinders, set to the minimum depth, were already in the tubes. The torpedo gunner and his mate were grimly alert, grasping the ball-ended levers that were to liberate the charge of compressed air. Slowly, ever so slowly, the British submarine swung to starboard, until her skipper knew that the fixed tubes were pointed straight towards their quarry. "Ready--fire starboard!" With a hiss as the air, hitherto compressed to two hundred pounds to the square inch, rushed from its compression chamber, the deadly missile sped on its way. Beyond the swish of the inrushing water that was automatically admitted to compensate the loss of weight caused by the speeding torpedo, not a sound broke the deadly stillness pervaded the interior of the submarine. Four seconds later a dull roar betokened the fact that one torpedo was sufficient for the work of destruction. "Blow main ballast tank," ordered the skipper. No need for caution now. The victor could appear on the surface with impunity. She rose almost vertically, for she had almost lost way. With the water pouring in cascades from her steel deck she flung herself free from the encircling embrace of the sea, and curtsied to the morning air. Hatches were quickly opened, and officers and men rushed on deck to see with their own eyes the result of their successful work. Already the _unterseeboot_ had vanished for the last time. An ever-widening circle of sullen water heavily tinged with oil, and surmounted by a cloud of pungent smoke that was slowly dispersing in the calm air, marked the spot where the luckless submarine had plunged to the bottom.