airtight. There was enough air in it to last for some time, but, sooner or later, it would no longer support life. Already, Tom thought, it seemed oppressive, though probably that was his imagination.
"I must get out!" he repeated frantically. "I'll die in here—soon."
Again he tried to shove back, the steel door. Then he repeated his cries until he was weary. No one answered him. He fancied once he could hear footsteps in the shed, and thought, perhaps, it was Andy, come back to gloat over him. Then Tom knew the red-haired coward would not dare venture back. We must do Andy the justice to say that he never realized that he was endangering Tom's life. The bully had no idea the tank was airtight when he closed it. He had seen Tom enter and a sudden whim came to him to revenge himself.
But that did not help the young inventor any. There was no doubt about it now—the air was becoming close. Tom had been imprisoned nearly two hours, and as he was a healthy, strong lad, he required plenty of oxygen. There was certainly less than there had been in the tank. His head began to buzz, and there was a ringing in his ears.
Once more ne fell upon his knees, and his
