Fifteen minutes brought them to Philipsburg. Captain Garland shot his plane upward a few hundred feet.
"Turn back, Captain," said Dr. Bird into the speaking tube. "Retrace your course a quarter of a mile farther north. At Bellefonte, turn back and go over the same ground another quarter of a mile north. Keep flying back and forth, working your way north, until I tell you to stop."
The plane swung around and headed back toward Bellefonte.
"Of course, we can't tell exactly what route he followed," said the doctor to Carnes, "but he was new on this run and it is safe to assume that he didn't stray far. We'll quarter the whole area before we stop."
Carnes watched the ground below them carefully. There was nothing about it to distinguish it from any other wooded mountainous country and his interest waned. He glanced aloft. The mail plane had disappeared in the distance and the sky was clear of aircraft. He turned again to the ground. It looked closer than it had before. He turned and looked at the duplicate altimeter. The plane had lost nearly a hundred feet elevation.
here's something wrong about this plane, Doctor," came Captain Garland's voice through the speaking tube. "It doesn't behave like it should."
"I guess we've found what we were looking for, Carnes," said Dr. Bird grimly. "What seems to be the matter, Captain?"
"Blessed if I know," was the answer. "It feels like a drag of some sort, like an automobile going through heavy sand. We're slowing down, though I am giving her all the gun I've got!"