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 Muk