ime they had reached a point almost above the field of ice from
the Arctic regions, and Jack was scrutinizing its full extent, commenting
the while on many peculiar features that attracted his attention.

"It's a Polar bear, all right, fellows," he announced, "and believe me
he's some size in the bargain. If I had a rifle along I wouldn't mind
dropping down there and rustling him. But what ails you, Tom? You seem
bothered about something. Gee! you're as white as a ghost!"

Lieutenant Beverly leaned forward and clutched the pilot's arm.

"Anything gone wrong with the motors, Tom?" he demanded hoarsely.

"I've just made a terrible discovery," replied Tom, trying to
control himself. "The worst has happened, and I'm afraid we're in
for a bad time!"

CHAPTER XIX

A DESPERATE CHANCE

"Tell us the worst, Tom!" cried Beverly hoarsely.

Jack tried to echo the words, but his tongue seemed to stick to the
roof of his mouth. He knew his chum well enough to feel assured that
no ordinary hovering peril could cause the other to look so ashen
pale. It must be a frightful catastrophe by which they were
threatened, Jack realized.

"The feed pipe! It must be choking up! Latterly I've more than suspected
the motors were doing poorer work than before!"

The others understood. Under ordinary conditions they would decide on
dropping to the ground for repairs; a task that might be carried out in a
brief time, or consume hours, everything depending on the condition in
which they found things.

But how utterly impossible to dream of doing anything like that now! Jack
looked down to where, in the declining light of the sun, he could see
that limitless sea of billowy water. How different indeed all might be
were their airship a seaplane, capable of floating on the surface of the
water and making a successful launch from it, just as a gull would do.

"I'll take a look, Tom!" Lieutenant Beverly called out. "Not that I doubt
what you say, but all of us will have to put our heads together; we shall
need all our wits if what you fear proves to be a fact."

Tom was more than willing, in fact he would have himself insisted on the
lieutenant or Jack doing this very thing. Pilots differ in plenty of
ways; and, as Beverly had said, one might hit on an answer to the problem
that had entirely escaped the others.

Jack said not a word, but almost held his breath while Beverly was making
his eager examination. The plane was not more than