“The old berg looks top-heavy,” Jack at one time called out.  “You can see that it leans toward the north; and sometimes I’ve thought it wobbled considerably, though that may have been the plane waving up and down.”

“No, you were right, Jack,” said Beverly.  “Its leaning that way tells that the warmer sea water has begun to eat at its base.  Before a great while the berg will roll over, and smash all that floe into bits.”

“I hope not when we’re on it, working at our motor!” Jack could not keep from exclaiming, looking with more interest than ever at the monster berg that had come all this distance from some glacier a thousand miles away, perhaps several times that distance, and would sooner or later lose itself in sub-tropical waters.

Lower still Tom took them.  All eyes continued to survey the field of ice, particularly in that extreme northern sector where Jack had reported lay the best place for landing.

“Once more in a circle so as to face the wind,” said Tom, “and then I mean to put it to the test.”

“Good luck to you, Tom!” said Jack.  “If ever you dropped as if you were falling on eggs, let it be now.  I’m going to hold my breath when we strike the ice, and only hope we don’t keep gliding along until we shoot off the edge into the sea!”

“Leave that to me, Jack,” came the assurance of the pilot.

After that no one said a word, for both Lieutenant Beverly and Jack Parmly realized that it would be dangerous to distract Tom’s attention from his work just at the most critical moment.

The sun had reached the horizon, and inside of a few minutes must vanish from view.  At that moment Tom shut off the engine, and made ready to alight!

CHAPTER XX

ON THE ICE FLOE

If ever Tom Raymond had need of skill and care it was then, for what might be an ordinary mishap ashore must be a fatal accident under the conditions by which they were faced.

But almost as lightly as a snowflake touches the ground he brought the wheels under the big bomber in contact with the ice.  Indeed, Jack could not tell for a certainty when the actual contact occurred; though immediately afterwards he found himself being shaken more or less as the heavy plane bumped along over the ice.

One peril still menaced them, which was that their momentum, unless halted, might carry them to the terminus of the floe, and plunge them over.  But Tom had taken all precautions, and allowed for everything, even an unusual slide on account of the smooth surface under the wheels.

Slower grew their progress, though the bumping continued unabated.  And finally they had come to a full stop, with still some little stretch of the ice field ahead.

Then Jack tried to yell, cowboy fashion; but, to his surprise and disgust, he could hardly make a sound above a whisper, his voice having failed him through sheer nervous excitement.