"We'll have to turn on one of the auxiliary air tanks," he said. "We've consumed more than the usual amount on account of the men working so hard, and we used one of the compressed air motors to aid the electrics. We'll have to open up the reserve tank."
"Very well, do so," ordered Tom.
But a grim look came to his face when Earle, returning a little later, reported with blanched cheeks:
"The extra tank hasn't an atom of air in it, sir!"
"What do you mean?" asked Tom, in fear and alarm.
"I mean that the valve has been opened in some way—broken perhaps by accident—and all the air we have is what's in the submarine now. Not an atom in reserve, sir!"
"Whew!" whistled Tom, and then he stood up and began breathing quickly.
Already the atmosphere was beginning to be tainted, as it always becomes in a closed place when no fresh oxygen can enter. Without more fresh air the lives of all in the submarine were in imminent peril. And even as Tom listened to the report of his officer, he and the others began gasping for breath.