"Put one on, Carnes, and climb in. I've got to get this spec set up before he gets too high."
The Douglass equipped with the Bird silencer, took the air noiselessly and rapidly gained elevation under the urging of the pilot. Dr. Bird clamped the gas-detecting spectroscope on the front of his cockpit and peered through it.
"Southwest, at about a thousand more elevation," he directed.
"Right!" replied the pilot as he turned the nose of his plane in the indicated direction and began to climb. For an hour and a half the plane flew noiselessly through the night.
"Bald Mountain," said the pilot, pointing. "The Canadian Border is only a few miles away."
"If they've crossed the Border, we're sunk," replied the doctor. "The trail leads straight ahead."
or a few minutes they continued their flight toward the Canadian Border and then Dr. Bird spoke.
"Swing south," he directed, "and drop a thousand feet and come back."