The engineer stepped up and went through the same process that the boy had gone through. He repeated the experiment twice more.
"You're right," he exclaimed, letting his hand drop to his side. "Your good sense is worth more than all my technical knowledge and training."
"The next question is to find out where the draft comes from. It must be from the outside somewhere," said Tad hopefully.
"Not necessarily, my boy. Of course it may be drawn down through crevices covering many feet of solid rock before reaching us. Then again, the air may come from some subterranean water course. As you know the mountains are full of them, channel upon channel, some high and broad enough to drive a coach and four through."
"Oh. I hoped—"
"Never mind regrets, boys. Wherever the air comes from makes little difference so long as it really is air. It is saving our lives."
"From what?" demanded Walter.
"From eventual suffocation. Were it not for that we would stand a good chance of dying before they were able to reach us."
The boys were thoughtful for a few moments.
"Hungry?" questioned the engineer.