Suddenly Fred started and almost uttered an exclamation.  In his nervous, apprehensive state, he was sure that one of their dusky foes had leaped from the side of the path and was crouching in front.

He drew his pistol and waited for the assault, which he was confident would come the next moment; but the seconds passed and all remained profoundly still.

With his weapon ready for instant use, he advanced a pace or two, touching the sailor as a command for him to remain motionless; but the chivalrous fellow would not obey, and was close behind him, when he stooped down and placed his hand on a piece of decayed limb that had fallen into the path.

“What a mistake,” muttered Fred, with a sigh, as he shoved it aside with his foot, explaining its nature to the wondering Johnston.

But it was only simple prudence to maintain unceasing vigilance, and he did not permit the error to lessen his watchfulness.  It was rather the reverse.

But the explorers were threading their way through a labyrinth of peril, the like of which they had never encountered before.

Fred had not gone a hundred yards further, when his companion once more caught his arm, and he turned about as before to learn the cause.

“What have you heard?” he asked, with his mouth almost against the ear of the other.

“There are some of ’em behind us, certain sure!”

“How do you know there are more than one?”

“By the sound—­there!”

The amazement of the two may be understood, when they not only detected the sound of footfalls, but discovered that instead of being at the rear as both thought, they were in front!

A party of natives were approaching from the Xingu, and the keener hearing of Johnston first discovered them.

The whites had stopped near a spot where a few rays of moonlight fell upon the trail, giving them a faint but needed view of the direction from which the danger threatened.

Neither spoke again, but with the utmost care and noiselessness, they stepped aside from the path and crouched among the undergrowth.

They had barely time to ensconce themselves in their new position, when the footfalls sounded more distinctly than before, and something in the nature of an exclamation was heard from one of the approaching savages.

It sounded more like the grunt of a pig than anything the listeners could call to mind, and Ashman feared it was notice of one warrior to his companions that he had discovered something amiss.

But if such were the fact, the natives would have stopped, while the cat-like steps were more audible than before, though the wonder to the watchers was that the parties continued invisible.

The eyes of both remained fixed on the faintly illuminated space, where they expected to catch sight of them, but the straining gaze failed to detect the most shadowy form.