The next two days were fair and the sea smooth. The great liner reeled off the miles with tremendous speed. As Billy had prophesied, the ship was so steady that there was very little sea-sickness and there was so much to be seen and done under these novel conditions that every waking hour was filled with interest. Two days later they picked up their convoy and all felt a very comforting sense of security in the presence of the destroyers with their business-like air and wicked looking guns. They kept pace with the liner, within easy reaching distance, occasionally exchanging signals, and keeping sleepless watch day and night over the huge transport. "The finest navy in the world!" cried Frank, with enthusiasm, as his kindling eyes rested on these "bulldogs of the sea." "That's one branch of the service where Uncle Sam has never fallen down. Man for man, gun for gun, and ship for ship, there's nothing in the world can beat them. Just watch them clean out that U-boat nest when they once get over there in force." "They'll do to them what Decatur did to the Barbary pirates years ago," said Bart. "Every other nation was paying tribute to them, but that idea didn't make a hit with us and we went in and wiped them off the face of the earth--or rather the face of the water. And what we did once, we can do again." Frank's eyes had been idly roaming over the sea while they were talking, but suddenly his gaze became fixed and he started to his feet. "Did you see that, fellows?" he demanded, sharply. "Where?" asked Billy "I didn't see anything," said Bart. "It looked like a flash of light on the water," explained Frank. "There it is again. Great Scott, it's a periscope!" Almost as he spoke, the forward guns on the liner roared their challenge, followed by the deeper bass of the guns from the nearest destroyer. In an instant there was great excitement, though without the slightest trace of panic. The ship swung around in response to a bell from the bridge and began to zigzag in a bewildering fashion. Then a great white furrow appeared in the sea and along that whitening lane came hissing a monster torpedo. Nearer and nearer it came with lightning speed straight toward the vessel. Had the liner kept its course the torpedo would have struck it amidships. As it was, it passed just back of the stern, missing it by not more than a dozen feet. The destroyers came racing like mad toward the spot from which the torpedo had been launched. No trace of the submarine was visible but the destroyers circled round and round the spot, dropping their deadly depth bombs in the hope of striking their unseen foe. Thousands of pairs of eyes watched for the result, while in their excitement their owners almost forgot to breathe. Minutes passed and then a mighty cheer went up. For on the waters appeared a gradually widening smudge of oil on which floated bits of wreckage that told their own story.