not taken a
vacation for two weeks, this was not an extraordinary thing to do,
notwithstanding the urgent work which they had started on the boat and
in the agricultural line.

The next morning the yaks were yoked, the wagons supplied with their
usual camping equipment, tools, weapons, provisions and the like, and a
start was made before ten o'clock.

By agreement a course was marked out farther south than was taken on
their previous trips, because they had never explored the country
immediately north of the South River, except beyond the falls, and it
was their aim to learn every foot of the territory.

On their way they passed the mysterious hole where George had his
experience, and the route was also close to the spot where Harry found
him when he was lost. Both places were again visited, so that samples of
rock might be taken from one of the places, and the Professor hoped the
clay bed on the small creek might indicate the proximity of other metals
than they had been able to find previously.

Late that evening they reached the edge of the main forest, and a camp
made for the night. Red Angel was with them. He was as happy at the
sight of the forest as an orang well could be. It was his delight to
exhibit his skill as a climber on these occasions, and where the woods
were dense he would spring from limb to limb with surprising agility.

During the night, as on several previous trips, Angel exhibited his
nervousness, which was attributed to the presence of some animal that
alarmed him, but otherwise nothing disturbed the camp.

"How far do you think we are from the falls?" asked Harry.

The Professor made a mental calculation as he replied: "We cannot be far
east of it; possibly five or ten miles at most, and it is very likely
several miles south. Since you suggest it, we might deviate from our
route and take it in, as to do so will not take up more than two hours
of our time. It interests me because I have not examined the place from
which our boat was taken. That is one of the mysteries I am most
interested in."

George was anxious to get a solution of that singular occurrence and
jumped at the opportunity to go there. A southwesterly course was at
once marked out, and after traveling about three hours George's alert
ear caught a sound, as he was at that time leading the advance. Running
back he called out: "Do you hear that peculiar sound?"

The wagon stopped. In the stillness around them they could hear