Jack said not a word, but almost held his breath while Beverly was making his eager examination.  The plane was not more than a thousand feet above the sea at most, and going very slowly now.

A short time elapsed.  Then Beverly completed his task.  The flight lieutenant looked more serious than ever, which told the story even before he uttered a single word.

Apparently the worst had come, and they were up against a question on the answer to which everything, even life itself, depended.

“I’m sorry to say it’s a positive fact, boys!” called out Beverly, and as both the others were straining their ears to catch what he said, they had no difficulty in hearing every word.

“It’s the supply pipe clogging then?” Tom asked.

“Yes,” came the quick answer.  “And while under some conditions I’ve been able to get along for a short time without dropping down, as a rule I’ve found it wise to look for a landing-place before things got to the point of desperation and avoid a fall, possibly in the midst of a German battalion.”

“No chance of our getting at it while afloat, is there?” Jack asked, although he knew what Beverly was bound to say.

“Not the slightest,” the other shot back.  “It might keep going for something like an hour, and then shut off the gas entirely.  Of course there’s always a possibility of a miracle happening, such as the obstruction being suddenly overcome; but I’m afraid that’s one chance in a million.”

“But can’t something be done, boys?  Must we just fold our hands, and meet our fate?” demanded Jack.  “What are you thinking about, Tom, for I can see a look in your face that we ought to know?  Have you an idea—­is there yet a hope that we can get a grip on this danger, and choke it?”

Tom’s face was still colorless, but there was a gleam in his eye, which Jack had discovered.  Perhaps after all it might be only the light of desperation, a determination to die game if a cruel fortune decreed that their time had come.  Jack could not tell.

“Yes, I have a plan,” said Tom quickly.  “Perhaps you’ll both call it a wild idea, and think I’m crazy; but desperate cases call for equally desperate remedies, and at the worst we’ll have a chance.”

“Good boy, Tom!” cried Jack.  “Just like you to hit on a plan!  Haven’t I known you to come to the front many times when things looked very black for us?”

“Tom, tell your scheme!” demanded Beverly.  “Things may develop faster than we suspect now, and if there’s any way to get around this trouble the sooner we start the better.”

“Of course,” Tom replied, “we’ll be taking the risk of smashing the nose of our craft when we strike, unless luck favors us.  I’ve landed on every sort of ground, from smooth velvety turf to bumpy stuff that almost joggled me to pieces; but I never before tried dropping on an ice-floe!”

Beverly and Jack stared hard at each other.  Apparently the idea struck them like a sudden blow, showing that neither had as yet contemplated such a thing.