It was evident that escape in that direction was almost beyond the bounds of possibility.
Awaiting a favourable moment when the nearmost sentry's back was turned, the fugitives crept cautiously down the slope, never halting till they came to the piles of empty casks that had served them so well less than twenty hours previously.
"Now what's to be done?" asked Hamerton.
"Have a shot at those steel ladders—the ones between the Zeppelin sheds."
"By Jove, smart idea of yours, old man! The sooner the better."
Without mishap the two comrades gained the base of one of the ladders that reared itself vertically to a height of nearly two hundred feet. It was to be a climb that would tax their powers of endurance to the uttermost.
"Gently does it," cautioned Hamerton. "One limb at a time, mind, and don't look down. Up you go."
With this parting injunction in his mind Detroit commenced to mount, making sure of each rung before he moved a step higher. He realized that a slip might result in the loss of his comrade's life as well as of his own.
The American was in excellent training, although somewhat handicapped for want of proper food. His muscles were flexible, his grip as firm as iron; nevertheless, by the time he gained the cross-platform connecting the ladders at a level slightly above the arch of the airship shed he was glad to sit down and rest.
"All right?" asked Hamerton anxiously.