It was at this juncture that Jared Long, peering out from the shadow of the wood, observed a larger log than any he had yet noticed, sweeping by within a short distance of shore.

It was without any branches, except a few near the top, but there seemed to be a number of big knots projecting from the upper side. He counted seven and they were all of the same size. Furthermore, unless he was mistaken, the huge tree, from some cause, was working closer to land.

Suddenly one of the knots moved!

The sentinel uttered an exclamation, for the startling truth flashed upon him with the quickness of lightning.

Each apparent knot was the head of a native!

With amazing coolness, the New Englander brought his Winchester to a level, and bang, bang, bang, he shattered three of the knots in quick succession.

He would not have stopped the frightful work even then, had not the other targets disappeared.

Awaking to their danger, the warriors, dropped down so low in the water that the log intervened between them and the deadly marksman.

Still the tree with its terrible load was approaching land. The natives were swimming toward shore and pushing it in front of them.

Long stepped back and roused the professor, placing his mouth so close to his ear that he was able to apprise him of what was going on, without being heard by their enemies.

Grimcke bounded to his feet, rifle in hand.

"We'll take them as they come out!" he replied, instantly grasping the situation.

The log was drifting lower down at the same time that it neared the land. Determined to confront the savages the instant they came forth, the explorers hurried along the edge of the wood, so as to be on the spot when the landing should be made. It was well they did so, for a more astounding discovery than the first, instantly followed the movement.

More than one of the trees that had floated by carried its human freight, and nearly a score of savages were crouching in the edge of the river, so flat on their faces that not one was visible from the spot where the sentinel was standing a moment before.

The natives, with a cunning that was never suspected, had crossed the Xingu above the rapids, where, as they knew, such a proceeding would not be anticipated by the explorers. Then, stealthily making their way to the bottom of the rapids, they first launched a number of trees and logs until, as may be said, the white man on guard should become so accustomed to them that they would cause no distrust.

If he should be tempted to scrutinize the first, he would learn that nothing was amiss and would let the rest go by unquestioned.

As a result, the natives had floated past the canoe and under the very nose of the sentinel without his detecting it.

The savage who swung the torch on the other side of the river probably meant it as a command for the daring raiders to make no further delay in their attack.

The group lying against the shore must have been puzzled by the sudden bombardment from the edge of the wood. They were so disconcerted, that instead of springing to their feet and charging upon the two defenders of the camp, half of them turned about, and diving deep into the stream, began furiously swimming for the other shore.

They must have concluded that there was a hitch somewhere in the programme, and the time for disappearing had arrived.

The other half, however, leaped to their feet, and, brandishing their spears and yelling at the top of their voices, ran swiftly in the direction of the whites, who were still firing their Winchesters.

"Get behind a tree!" shouted the professor, who had a wholesome dread of the poisoned weapons, and who lost no time in availing himself of the nearest shelter.

But he did not cease to use his rifle. The cartridges in his magazine were running low, and it was necessary to exercise care in aiming, for a few precious seconds must be consumed in extracting an additional supply from the belt at his waist.

But Jared Long declined to follow the sensible advice and example of his friend. Scorning to seek shelter, even from such terrible weapons, he blazed away, making nearly every shot tell.

It was not until he saw a knot of savages working round with a view of getting behind him, that he fell back a few paces, though still exposed. The wonder was ............