Twilight is of short duration in the low latitudes, and the wish of the four white men was to be back in camp at the end of an hour, by which time night would be fairly upon them.  But the moon was at its full and would serve them better than the twilight itself.

The German and New Englander, therefore, moved away from camp, following the course of the Xingu, while their two friends quickly vanished in the forest.  Each carried his repeating Winchester and his Smith & Wesson.

Ashman felt some misgiving because of the trail leading into the woods from a point so near the camp.  It seemed likely to have been worn by the inhabitants of some village near at hand, though it was possible that the innumerable feet of wild animals on their way to and from the river may have been the cause.  The upper waters of the Xingu are remarkably clear and pure, a fact which rendered the first theory most probable.

The explorers had landed in a dangerous region, as they were destined to learn very soon, and the experience of the couples who took routes at right angles to each other was of the most thrilling character.

It has been stated that the progress of the canoe had been checked, as was often the case before, by the rapids of the Xingu, which could be passed only by carrying the canoe and luggage to the smoother waters above.  It was apparent that the river frequently overflowed its banks, for immense quantities of driftwood lined both shores, while the vegetation had been swept away to that extent that a space of a dozen feet from the margin of the stream was comparatively free from it.  Thus both parties found the travelling easy.

The rapids were a hundred yards wide, more or less, and, with such a steep incline, that the foamy waves dashed hither and thither and against each other with the utmost fury, sending the spray high in air and sweeping forward with such impetuosity that it seemed impossible for the strongest craft under the most skilful guidance to shoot them.  The explorers studied them with great interest as they ascended the left bank.

It was inevitable that in a country with such excessive vegetable growth, every part of the Xingu should show much floating timber.  The logs which plunged through the rapids played all manner of antics.  Sometimes they leaped high out of the waters, like immense sea monsters, the out-spreading limbs showing a startling resemblance to the arms of a drowning person mutely appealing for help.  Then a heavy trunk would strike a rock just below the surface, and the branches, dripping with spray, swept over in a huge semi-circle.  The roar and swirl suggested the whirlpool below the falls of Niagara, one of the most appalling sights in all nature.

CHAPTER II.

A trio of enemies.

At last, when the full moon was shining, the two men stood at the head of the rapids and surveyed their surroundings before setting out on their return to camp.