It was arranged that Quincal and Jared Long should mount guard until midnight, when they would give way to Pedros and the professor.

This would leave Bippo and Ashman free from any duty, their turn to come the following night.
Ashman, however, insisted on taking a part which was somewhat original in its nature.

He was confident that if the savages found it impracticable to cross the Xingu in sight of the explorers, they would pass down stream and endeavor to do so, at a point where they could not be observed by those in camp.
He meant, therefore, to station himself so as to be able to detect such a movement.

With his repeating rifle at command, he was sanguine of defeating the attempt, even though made by a score of enemies.
But for the peculiar contour of the banks on both sides, the whites could have done much better by simply paddling the canoe a quarter of a mile down the river and then hiding under the overhanging vegetation; but it has been explained that the Xingu, when its volume was swelled by rain, had swept the shores with such violence that they were bare for a dozen feet from the water.
Such a movement, therefore, would have to be made in the full light of the moon, and would, therefore, be plainly perceptible from the opposite bank--a fact which rendered the precaution of no avail.
All conceded the wisdom of Ashman's plan.

The Professor urged him in case he found himself growing drowsy, to return at once to camp and allow one of his friends to take his place.