“We portage here,” he explained.  “Current swift there—­mebby go over fall!”

A short carry of two or three hundred yards brought them to the cataract.  It was, as Mukoki had said after his long trip of exploration a few months before, a very small fall, not more than a dozen feet in height.  But over it there was now rushing a thundering deluge of water.  An easy trail led to the stream below it, and no time was lost in getting under way again.

Although they had traveled fully forty miles since morning, the day had been an easy and most interesting one for the three adventurers.  On the swift current of the chasm stream they had worked but little, and the ceaseless change of scenery in this wonderful break between the mountain ridges held an ever-increasing fascination for them.  Late in the afternoon, the course changed from its northeasterly direction to due north, and at this point there was an ideal spot for camping.  Over an extent of an acre or more there was a sweeping hollow of fine white sand, with great quantities of dry wood cluttering the edge of the depression.

“That’s a curious spot!” said Wabi as they drew up their canoe.  “Looks like—­”

“A lake,” grunted Mukoki.  “Long time ago—­a lake.”

“The curve of the stream right here has swept up so much sand that the water can’t get into it,” added Rod, looking the place over.

Wabi had gone a few paces back.  Suddenly he stopped, and with a half shout he gesticulated excitedly to his companions.  Something in his manner took Rod and Mukoki to him on the run.

When they came up the Indian youth stood mutely pointing at something in the sand.

Clearly imprinted in that sand was the shape of a human foot, a foot that had worn neither boot nor moccasin when it left its trail in the lake bed, but which was as naked as the quivering hand which Wabigoon now held toward it!

And from that single footprint the eyes of the astonished adventurers traveled quickly to a hundred others, until it seemed to them that a dozen naked savages must have been dancing in these sands only a few hours before.

And Rod, glancing toward the driftwood, saw something else,—­something toward which he pointed, speechless, white with that same strange excitement that had taken possession of Wabigoon!

CHAPTER XIII

THE THIRD WATERFALL

The others followed Rod’s arm.  Behind him he heard the gentle click of Wabigoon’s revolver and the sharp, vicious snap of the safety on Mukoki’s rifle.

From beyond the driftwood there was rising a thin spiral of smoke!

“Whoever they are, they have certainly seen or heard us!” said Wabi, after they had stood in silence for a full minute.

“Unless they are gone from camp,” replied Rod in a whisper.

“Keep eyes open!” warned Mukoki as they advanced cautiously in the direction of the smoke.  “No can tell what, I guess so!”