Chapter Five

Mr. Berg is Suspicious

Not for long did the young inventor endeavor to break his way out of the water-ballast tank by striking the heavy sides of it. Tom realized that this was worse than useless. He listened intently, but could hear nothing. Even the retreating footsteps of Andy Foger were inaudible.

"This certainly is a pickle!" exclaimed Tom aloud. "I can't understand how he ever got here. He must have traced us after we went to Shopton in the airship the last time. Then he sneaked in here. Probably he saw me enter, but how could he know enough to work the worm gear and close the door? Andy has had some experience with machinery, though, and one of the vaults in the bank where his father is a director closed just like this tank. That's very likely how he learned about it. But I've got to do something else besides thinking of that sneak, Andy. I've got to get out of here. Let's see if I can work the gear from inside."

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