Before he started, almost, Tom knew that it would be impossible. The tank was made to close from the interior of the submarine, and the heavy door, built to withstand the pressure of tons of water, could not be forced except by the proper means.
"No use trying that," concluded the lad, after a tiring attempt to force back the sliding door with his hands. "I've got to call for help."
He shouted until the vibrations in the confined space made his ears ring, and the mere exertion of raising his voice to the highest pitch made his heart beat quickly. Yet there came no response. He hardly expected that there would be any, for with his father and Mr. Sharp away, the engineer absent on an errand, and Mra Baggert in the house some distance off, there was no one to hear his calls for help, even if they had been capable of penetrating farther than the extent of the shed, where the under-water craft had been constructed.
"I've got to wait until some of them come out here," thought Tom. "They'll be sure to miss me and make a search. Then it will be easy enough to call to them and tell them where I am, once they are inside the shed. But" He paused, for a horrible fear came over him. "Suppose they should come—too late?" The tank was
