ubtedly any movement to
the pack ice must be caused by some action of the giant berg. Was that
mountain of ice about to take the plunge at last, and turn over, its base
being eaten away to such an extent that the whole had become top-heavy?

Once again did Jack turn his startled eyes to the left. He could not get
it out of his mind how terribly suggestive that "bow" on the part of the
berg had been.

There it was, coming again! Perhaps the wind had grown stronger since
they dropped down upon the ice, and was adding its force to the action of
the waters.

Jack found himself unable to hold in any longer. If such a dreadful peril
hung over them it was time his companions knew the need of haste in
getting free from that doomed field of ice. So he put all doubts behind
him and gave tongue.

"Hurry, hurry, Tom! The iceberg is acting queerly. It's tottering as if
ready to roll over on us! Don't you see how it acts, Tom?"

CHAPTER XXII

WHEN THE ICEBERG ROLLED OVER

Fortunately Tom had everything ready for an immediate start, acting under
orders, Jack and Beverly having previously changed the position of the
big plane, so that it now faced the run taken when landing.

This brought the wind back of them; but that would be an asset rather
than a detriment. They had also gone hastily over the course to make
absolutely certain there was no break, or other trap, which might give
them serious trouble.

"Jump aboard, both of you!" cried Tom, still keeping his head--a lucky
thing, since to get "rattled" in such a crisis might prove fatal.

The beating of the engine and the whirr of the propellers announced that
they were off. On the comparatively smooth ice it was easy to make a
start unassisted by mechanics or hostlers.

Jack's heart seemed to be in his throat, and he waited in feverish
suspense to learn whether success or failure was to be their fortune.
Faster now grew their progress, but would the stretch of ice prove a
long enough area to give them the necessary momentum?

Every second they expected to hear horrible grinding noises from behind,
such as must accompany the toppling over of the berg. Even the splash of
waves against the further side of the big ice-floe seemed like the
pounding of a monster hammer, at least to Jack's excited imagination.

They were now drawing perilously near the brink. Was Tom ever going to
elevate the plane and attempt the rise from the flat surface of the ice?

Just when it