"Here's trouble, all right!" grumbled Beverly, as he turned, looking to where Jack was pointing, and also discovered something moving.

Tom dropped his monkey-wrench. Something else besides a tool of that kind would be needed to defend them against the claws and teeth of such a bulky monster as a huge Polar bear.

All of them could now make the animal out as Beverly concentrated the little ray of light upon him. The beast was advancing slowly, but pugnaciously, sniffling the air, and evidently furiously hungry on account of his prolonged cruise upon the icefield, deprived of his customary fish meals.

"What ought we do, Tom?" Jack called out hurriedly. "If we retreat, like as not he'll muss things up around here, and maybe ruin our plane for us."

"We must keep him away!" announced Lieutenant Beverly. "It would mean death to us all if he got to tumbling around and smashed some of the parts of the machine."

As he said this he fumbled about his person, producing the automatic pistol with which he usually went on his flights; and without which few air pilots venture to enter into combat with enemy fliers.

Tom duplicated his act immediately, while Jack, at the same time, secured his weapon from the place where he kept it when in his seat. So, after all, things did not seem to be altogether favorable to Bruin; and had the bear only known what he was up against possibly he would have found it discreet to back off and let the three strange creatures alone.

"Be sure to hold your fire, boys!" Lieutenant Beverly ordered, taking command. "We must be like old Put at the battle of Bunker Hill, and wait till we can see his eyes clearly. It's going to be hard to drive off that big rascal with only pistols! Aim for the spot back of his foreleg if you can; that may reach his heart!"

There was not much time for preparation, since the bear kept advancing at the same shuffling gait. Tom tried shouting at him, hoping the sound of a human voice might cause the beast to alter his intention, and turn back.

The bear did stop, and thrust his muzzle further out as though to get a better whiff of the queer animals against which he found himself pitted.

"Didn't go, Tom, for he's coming on again!" cried Jack.

"Get ready to give him a volley," the lieutenant ordered. "Tom, move off a bit to the right, and I'll go to the left. That may upset his calculations some; and besides, we'll have a better chance to bore in back of his forelegs. Jack, stand where you are, and shoot when we do!"

"I'm game!" came the steady reply.

Both the others made a quick move, and the bear found himself facing three separate points of peril. He growled fiercely, and came on again, straight toward the plane, which seemed to have aroused his curiosity. Perhaps he fancied it was some monster bird that would afford him more than one good meal.

"Give it to him, everybody!" suddenly shouted Lieutenant Beverly.

Hardly had he uttered the last word than there was a rattle of firearms as the three of them discharged their weapons. There arose a mighty roar of anger as the bear felt the sudden pain of bullets entering his flesh.

"Again! He's staggering, but full of fight yet!"

Once more the pistol shots rang out. The bear was moving, but seemed to be growing quite weak and confused, for once he fell half over, though managing to recover and push on.

It took several more rounds before the huge bulk rolled over, gave a few spasmodic kicks, and then expired.

"Bully work, boys!" shouted Jack, as he hurried forward to take a close-up view of their victim. "Gee whiz! but isn't he a buster though? Never did I dream I'd help bring down a real Arctic white bear! And just to think of the queer conditions of this hunt, too, will you? I wager, now, there never was one like it—by airplane at that!"

After one look at the bear Tom returned to his task. Shooting game was all very fine, but he had business of a different character to call for his attention just then.

"Wonder if the old chap has got a mate around?" suggested Jack, a sudden thought causing him to survey the ice-floe as seen under the faint light of the stars that were beginning to show in the heavens above.

"Not one chance in a thousand he had company," Beverly insisted; "but no harm in your keeping a wary eye about, Jack, while Tom gets things in shape again. I have to stay here with the light. If you've a sharp knife what's to hinder you from taking one of his claws for a trophy?"

"I'll do that same. Thank you for reminding me, Colin! Some fellows I know are such Doubting Thomases you have to be in a position to prove everything you tell them. Tom, loan me that knife of yours, please. It's got an edge like a razor to it, and those paws look simply immense."

"Make haste about it, for we'll soon be ready to skip out of this place,"
Tom warned him as he handed over the knife.

Jack began to work industriously. He found he had undertaken no mean job when he contracted to sever one of the front paws of the dead Polar bear. Not only did he have to cut through ligaments and tough skin, but the bones themselves gave him no end of trouble.

He solved this by finding the heavy monkey-wrench, and using it as a hammer, with the knife in place, thus actually severing the paw complete after considerable trouble.

"There, isn't that a regular beauty to show?" he demanded, holding up the result of his labor. "I feel something like a young Indian warrior who's just killed his first grizzly, and means to hang the claws about his neck to prove his bravery."

He stood looking down at the monster bear for a minute, debating something in his mind.

"I wonder now," Jack finally observed, "if we could eat that bear meat, supposing something happened to keep us marooned on this ice for weeks at a stretch? What do you think about it, Tom?"

"It might be possible, if we got in a bad pinch and were almost starving," came the reply. "But you must remember we'd have to swallow it raw, because we haven't any means for making a fire; and trying to kindle a blaze on the ice would be a tough job."

"Then I'm glad to know we don't have to depend on bear meat to keep us from starving," Jack announced. "Pretty nearly through, Tom?"

"Five minutes more ought to see us ready to start. I'm pretty hungry though and would like something more to eat. You boys ate a good deal, but you called it 'a snack,' and not 'supper.'"

"On the whole," Colin suggested, "perhaps we'd better leave the supper until we get to moving smoothly again. Things ought to taste better if we feel we've got the bulge on this engine trouble for fair."

Jack did not try to urge any undue haste. Nevertheless he looked several times in the quarter close by where the big berg raised its cone, as if his uneasiness now might be wholly concerned with its possibilities for making fresh trouble.

Was it imagination, or some sort of optical delusion that made the tip of the huge berg seem to come lower and lower, then draw back again as if making a ceremonious bow like a dancing-master?

Jack gasped, and opened his lips to cry out, but thinking better of it restrained the temptation. They could not get away until the repairs were complete. At the same time, while trying to make himself believe he had magnified the thing, he was conscious of a louder grinding noise than any heard up to that moment.

Tom was putting the finishing bolt in place. A few more efforts and he would be able to announce that his task had been completed. Jack became conscious of a peculiar undulating movement to the ice under his feet. It was just the same as he could remember experiencing when on skates, and going at full steam over a thin section of ice that must have easily broken under his weight only for the speed with which he crossed over.

Was the ice floe about to break up? Would it result in several smaller sections separating from the main stem, none of which might be of a size to allow them sufficient room for making a start?

The thought alarmed Jack. He also knew that undoubtedly 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?"