"Starboard bow, Dastral! Look at 'em! What are they? Not mines, surely. Look like porpoises, only they're not dark enough, and they don't tumble about much." Dastral peered over the side of the cockpit and looked down. "Can't say," he ejaculated. "Let's go down a bit lower, old man," said Fisker. "Aye, aye. Hold tight!" cried the pilot, for he noticed that Jock was standing up and leaning over, unstrapped. "Right away! I'm all right," replied the observer, squatting down, and pressing his knees against the knee-board, which is the life-line of the aeroplane. And down they went in a graceful nose-dive till they were within five hundred feet of the surface of the water, with the engines shut off. Then, as they flattened out, both men peered over the side again, and Dastral was the first to exclaim:-- "Porpoises be hanged! They're German mines. A whole string of them floating about in the fairway, ready for the first ship that comes along. The dirty Huns!" "Snakes alive! So they are. Now I can make them out quite plainly; I can even see the horns and contacts through my glasses. Phew! There'll be a deuce of a mess shortly unless they're cleared up." "Look alive, old man, or there'll be trouble!" shouted the pilot. "How so?" "See that ocean tramp coming up Channel. She's a seven thousand tonner, and her cargo's worth a couple of hundred thousand. She'll be right on the string of mines directly, and then--gee whiz!--there'll be fireworks, and another valuable cargo will have gone to Davy Jones' locker." The mine-sweepers were about a couple of miles away by this time, but the Commodore of the little fleet had seen the rapid nose-dive of the hornet, and knew that something unusual was happening. He had already strung out the signal for a boat to detach its nets and proceed at full steam to the spot, for he thought that the machine was coming down with engine trouble. It was his duty, therefore, to save the men, and, if possible, salve the aeroplane also. Dastral saw the signal through his glasses, and watched the vessel cast off her nets to come up. His immediate concern, therefore, was for the tramp steamer surging up Channel, and nearing the end of her long voyage from Valparaiso to London. At all costs to the aeroplane, she must be saved from the deadly mines towards which she was now heading directly. The tide was with her, and she was coming up rapidly. In another five minutes she would be in the cunningly laid trap. For the moment, Dastral continued to circle over the mine bed, hoping thereby to warn off the tramp. Of this she appeared to take no notice, though undoubtedly a score of eyes were watching his gymnastic gyrations from the deck and bridge of the vessel. "Try the gun, Jock. Quick!" "Rip-r-r-r-r-r!" went the Lewis gun, as Jock pressed the button and fired off half a drum of ammunition. Even yet, the tramp steamer did not seem to understand, for her captain did not charge her course.