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 a faint murmuring sound.
"Do you know what that is?" The boys looked at each other. "I think," continued the Professor, "that must be the falls."