The ship gave a sudden lurch. "We're sinking!" cried Bill, rushing to the conning tower from the engine-room. "That's only the action of one of the emergency levers," said the professor calmly. "It forces compressed air into the tanks the more quickly to empty them of water. I think we are safe." "What is it?" asked Mark, as, followed by Jack, he came forward. "We tried to do the torpedo act to one of Uncle Sam's ships," explained Andy. The electric lights had been switched on, and, with the _Porpoise_ flooded with the bright beams, those on board waited anxiously for what was to happen next. Suddenly an upward motion was experienced. The next instant the craft bounced out of the water and fell back in a smother of foam, shaking and shivering, alongside a small armored warship that was anchored about two miles and a half from shore. "Open the manhole," commanded Mr. Henderson. Mark sprang up the iron ladder that led to the opening in the deck of the _Porpoise_ and threw back the cams that held the heavy iron in place. Then he swung the cover back and stepped out on the small platform, followed by the professor, Andy and Jack. They looked up to find themselves observed by a curious throng that crowded to the rail of the warship. [Illustration: A CURIOUS THRONG CROWDED TO THE RAIL OF THE WARSHIP.--_Page 28._] "What are you trying to do? Ram me with a new-fangled torpedo?" asked an angry voice, and a man in a gold laced uniform, who, from his importance plainly showed himself to be the captain of the ship, shook his fist at Mr. Henderson. "I might ask what right your ship has to get in my path," replied the inventor. "It was all an accident." "Mighty queer," muttered the naval commander. "Looks very suspicious. How do I know but what you're a torpedo from some foreign nation?" "Because this is not a torpedo," replied Mr. Henderson. "It is a new submarine boat of my invention, and I was giving it a trial spin." "I guess you'd better come aboard and do your explaining," went on the captain. "I don't like the looks of things. Lower a boat!" he shouted, "and bring those chaps to my cabin. I want to question them." It did not suit Professor Henderson to have his plans upset in this fashion. Nor did he care to give a detailed description of his ship to officers of the war department. He had many valuable inventions that were not patented. So he determined to outwit the pompous commander of the cruiser. The noise made in preparing the small boat for lowering over the side of the big ship could be plainly heard. "Go below, all of you, and as quietly as you can," whispered Mr. Henderson. Andy, Mark and Jack obeyed. At that instant the side of the warship was almost deserted, for the sailors who had gathered to observe the _Porpoise_ had gone to lower the small boat. No sooner had Jack, who was in the rear, disappeared through the manhole than the professor, with a quick jump, followed him.