IT did not take the explorers long to pass a group of islands not far upstream, one of the landmarks that Otari had told them about, and as the islands were a number of miles from the village, they felt that they were making a rapid start.

The country was gradually becoming wilder and more beautiful, but with this came an increase in the number of dangerous obstacles that had to be avoided. On the shore the jungle was denser than they had ever seen it before. In many places, to attempt to penetrate its depths would be difficult and perilous, and disaster would come upon anyone who would not blaze a trail.

The variety of fauna was still greater, and many new specimens did the naturalists add to their already large collection. Birds and beasts and reptiles all fell at the report of the explorers’ rifles.

Finally they came to a wide tributary, which forged off from the main stream, making the two rivers form a perfect V. This was the second of Otari’s landmarks, and the explorers felt that another important distance had been covered.

“The current’s rather rough,” said Bob, his eyes following the course of the tributary.

The explorers passed the stream by, not thinking it wise to chance an exploration of it.

The next day their adventurous spirits proved their own undoing. They had been paddling constantly after the morning meal when suddenly they came upon another tributary, this time branching out at right angles from the main stream. There was something about that river that made the explorers want to follow its rough course.

“Probably doesn’t continue far,” was the opinion given by Mr. Holton. “Let’s turn the boats up for a considerable distance. We may come across something totally different.”

The others agreed, for there was a possibility of finding almost anything in this out-of-the-way tributary.

“But we must not stray too far from the TapauÁ,” warned Professor Bigelow, as the crew turned the boats in that direction.

For the first hour the country remained much the same. Then they reached a region where rocky crags protruded out from the shore, making it necessary for the crew to be doubly careful in guiding the boats. And with this danger came the possibility of another, for the current was growing stronger. A terrific rapids could be only a short distance downstream. At last, much to the surprise of all, they came to another river, running at right angles to the one they were on.

A thought struck Bob.

“Do you remember that tributary we passed yesterday that formed a V with the TapauÁ?” he asked. “Well, I’ll bet this is it. It runs almost parallel with the TapauÁ, and we’ve come upon it by taking this course that runs at right angles.”

“By George, you may be right,” agreed Mr. Lewis, suddenly grasping the meaning. “What say we turn down it and see if Bob isn’t right? If he is we’ll gradually fork over to the TapauÁ and be where we were yesterday afternoon.”

The others did not object, for they were curious to know whether or not Bob was right.

The current gradually grew stronger, carrying the boats ahead at a much swifter pace. Although this afforded the crew a chance to rest, it worried the explorers, for it was plain that a rapids was somewhere ahead.

They paddled on, however, confident that they were not near enough to be in danger.

“We’ll continue for a while,” said Mr. Holton. “Then we may be able to find out what is ahead of us.”

The words had scarcely left his mouth when the boats rounded a corner, not two hundred feet above a seething, boiling rapids, its waters rushing madly past protruding rocks.

There was no time to lose. Something must be done at once!

“Stop the boats!” cried Mr. Lewis in Portuguese to the crew.

The Indians heard, and struggled with all their might against the rapidly increasing current, but their efforts were in vain. The boats had gained too much momentum.

The cruel water carried them on at terrific speed, which was increased several fold when they went into the rapids. Then they realized that there was little use trying to stop. The forces of man were puny indeed compared to that terrific onslaught of foam.

“Make for the middle of the stream!” commanded Mr. Holton. “Even then it will tax our efforts to the utmost.”

The whites grabbed poles and what other objects they could find and did their part in keeping the foremost boat at as near the middle of the river as they could. But even with the added help it was extremely difficult to guide straight.

The crew had the paddles, and they were doing their best to steer the boats away from the banks. They succeeded fairly well, for the river was still several score feet wide.

But grave misfortune awaited them.

Not far away was a small island, stretching several hundred feet along the course of the river. The distance between the river bank and the island shore was little more than twenty feet, hardly room enough for the boats to get through. And to make matters worse, there were several large boulders protruding near the bank. Disaster seemed almost certain!

In the face of this grave danger the explorers remained calm, determining to save themselves and the boats if it were at all possible. But how?

With sinking hearts they saw the boats head directly for the rocks, where they would immediately be dashed to pieces.

“We must—we’ve got to do something!” cried Professor Bigelow, rapidly losing his nerve.

Bob and Joe were nearest the bank, and anything that could be done was up to them.

Summoning all his power, Joe thrust a sturdy pole into the roots of a large tree that grew almost in the water. He little expected anything to come of the act, but it was a last resort.

Much to the surprise and relief of all, the sudden impact forced the boat back into midstream, although Joe was nearly thrown overboard by the clash.

Bob drew a sigh of relief. A narrow escape! Perhaps the closest they would ever be to death and yet evade it.

But what of the other boat? The whites were so intent upon guiding the one they were in that they completely forgot about the one that trailed.

They quickly glanced around, to see that it had escaped also, and was dashing along behind. How the good luck was brought about they never knew.

“That was a wonderful act on your part,” praised Mr. Holton, turning a moment to Joe.

The latter shook his head.

“Don’t know how I happened to think of it,” he said modestly. “I didn’t expect any good from it, though.”

The others also took part in the commendation, and Joe was glad to turn the conversation to their present predicament.

“Looks like we have a fair chance now,” he remarked, glancing far ahead.

Then suddenly they struck a seething whirlpool and were spun around broadside to the terrific current.