But the amazing part of it was that the wind came sweeping along with a loud roar—­as if it brought with it the noise of a large mill or factory, though nothing of the kind was to be found out there on the ice.  They had walked to the west of the big island, Valen; now they thought they were nearing the north shore.  Suddenly the wind began to blow more and more, while the loud roaring increased so rapidly that they began to feel uneasy.

All at once it occurred to them that the roar was caused by the foaming and rushing of the waves breaking against a shore.  Even this seemed improbable, since the lake was still covered with ice.

At all events, they paused and looked about.  They noticed far in the west a white bank which stretched clear across the lake.  At first they thought it was a snowbank alongside a road.  Later they realized it was the foam-capped waves dashing against the ice!  They took hold of hands and ran without saying a word.  Open sea lay beyond in the west, and suddenly the streak of foam appeared to be moving eastward.  They wondered if the ice was going to break all over.  What was going to happen?  They felt now that they were in great danger.

All at once it seemed as if the ice under their feet rose—­rose and sank, as if some one from below were pushing it.  Presently they heard a hollow boom, and then there were cracks in the ice all around them.  The children could see how they crept along under the ice-covering.

The next moment all was still, then the rising and sinking began again.  Thereupon the cracks began to widen into crevices through which the water bubbled up.  By and by the crevices became gaps.  Soon after that the ice was divided into large floes.

“Osa,” said little Mats, “this must be the breaking up of the ice!”

“Why, so it is, little Mats,” said Osa, “but as yet we can get to land.  Run for your life!”

As a matter of fact, the wind and waves had a good deal of work to do yet to clear the ice from the lake.  The hardest part was done when the ice-cake burst into pieces, but all these pieces must be broken and hurled against each other, to be crushed, worn down, and dissolved.  There was still a great deal of hard and sound ice left, which formed large, unbroken surfaces.

The greatest danger for the children lay in the fact that they had no general view of the ice.  They did not see the places where the gaps were so wide that they could not possibly jump over them, nor did they know where to find any floes that would hold them, so they wandered aimlessly back and forth, going farther out on the lake instead of nearer land.  At last, confused and terrified, they stood still and wept.

Then a flock of wild geese in rapid flight came rushing by.  They shrieked loudly and sharply; but the strange thing was that above the geese-cackle the little children heard these words: 

“You must go to the right, the right, the right!” They began at once to follow the advice; but before long they were again standing irresolute, facing another broad gap.