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. The young man gave his promise, and, bidding them good-by, he began stealing down the stream, keeping as closely within the wall of shadow as he could, and advancing with as much care as though he saw the fierce savages across the Xingu watching for just such a movement.

The peculiar nature of the ground rendered progress easy, and he paused after going about a furlong, believing he had advanced sufficiently far to accomplish what he wished.

The essential work of Ashman was to cover one-half the distance between him and the camp, the further half being under the surveillance of the guards on duty there. Since he could also overlook the stream equally far in the opposite direction, it will be seen that the savages would have to make their crossing nearly a fourth of a mile below the camp to escape observation.

All this was on the theory that the lone sentinel was really able to scan the space with sufficient clearness to detect anything of the nature apprehended, and that the savages themselves had no suspicion of any such extra care on the part of their enemies.

The astonishing brilliancy of the moonlight will be appreciated, when it is stated that Ashman felt not the least doubt of his ability to meet every requirement of his self-assumed duty.

Well aware, from previous experience, of the insidious approach of slumber to the most vigilant sentinel, when unable to keep in motion, he avoided sitting down, even though he never felt more wakeful. So long as he stood erect, there was no danger of his lapsing into unconsciousness.

Another indispensable requirement was that he should not be tempted into venturing from the shadow where he stood, for such an act was liable to bring about discovery and defeat the very object that had brought him thither.

The moon was so nearly in the zenith that the shade from the edge of the forest did not project halfway across the open space to which we have alluded. It was in this partial gloom that the young man took his station, placing himself as far back as he could without standing among the trees themselves.