On it came, that rolling sea of flame, with inconceivable rapidity, gathering strength as it advanced.

The demon of destruction spread its red wings to the blast, rushing on with fiery speed; and soon hill and valley were wrapped in one sheet of flame.
"It must have been the work of the Indians," said Louis.

"We had better make a retreat to the island, in case of the fire crossing the valley.
We must not neglect the canoe; if the fire sweeps round by the swamp, it may come upon us unawares, and then the loss of the canoe would prevent escape by the lake.

But here are the girls; let us consult them.
"It is the Indian burning," said Indiana; "that is the reason there are so few big trees on that hill; they burn it to make the grass better for the deer." Hector had often pointed out to Louis the appearance of fire having scorched the bark of the trees, where they were at work, but it seemed to have been many years back; and when they were digging for the site of the root-house _[FN: Root-houses are built over deep excavations below the reach of the frost, or the roots stored would be spoiled.]_ below the bank, which they had just finished, they had met with charred wood, at the depth of six feet below the soil, which must have lain there till the earth had accumulated over it; a period of many years must necessarily have passed since the wood had been burned, as it was so much decomposed as to crumble beneath the wooden shovel which they were digging with.
All day they watched the progress of that, fiery sea whose waves were flame--red, rolling flame.

Onward it came, with resistless speed, overpowering every obstacle, widening its sphere of action, till it formed a perfect semicircle about them.