As they hastened back over the ice-belt at the foot of the cliffs, a
loud boom rang out in the distance and rolled in solemn echoes along the
shore.

"There goes a gun," exclaimed Tom Singleton, hastily pulling out his
watch. "Hallo! do you know what time it is?"

"Pretty late, I suppose. It was afternoon, I know, when we started, and
we must have been out a good while now. What time is it?"

"Just two o'clock in the morning!"

"What! do you mean to say it was _yesterday_ when we started, and that
we've been walking all night, and got into _to-morrow morning_ without
knowing it?"

"Even so, Fred. We have overshot our time, and the captain is signalling
us to make haste. He said that he would not fire unless there seemed
some prospect of the ice moving, so we had better run, unless we wish to
be left behind; come along."

They had not proceeded more than half-a-mile when a Polar bear walked
leisurely out from behind a lump of ice, where it had been regaling
itself on a dead seal, and sauntered slowly out towards the icebergs
seaward, not a hundred yards in advance of them.

"Hallo! look there! what a monster!" shouted Fred, as he cocked his
musket and sprang forward. "What'll you do, Tom, you've no gun?"

"Never mind, I'll do what I can with the hammer. Only make sure you