The mountains, the forests, the headwaters of the rivers which help to make the Amazon, were under their feet. Now and then they swept over a point of light which denoted the presence of a small town. Occasionally the cry of frightened wild beasts—the vicious mountain lion, the savage tiger cat, the prowling puma—came up to their ears.

After a short run to the southeast, Ned wheeled about and struck straight off to the east. The wind was growing stronger, and the Nelson was not making as good time as the boy desired.

There was a fierce current about the top of Mt. Sorata, which is something over 21,000 feet in height, and again Ned swung off to the north. Dropping down, then, he swept into the valley of the Beni river, which joins the Madeira river, some distance beyond the Bolivian border.

He knew that at the eastern rim of Bolivia there was a series of high mountain ranges which would protect him from the drifts blowing over from the Atlantic—Serre Geral, Serre Paxecis, Serre Aguapehy—and he reasoned that he could make better speed under the lee of these elevations. So he swept down the valley of the Beni until it joined with the Madeira, crossed a line of hills, and made for the Serre Geral range, something under a hundred miles away.

As the Nelson cleared the valley, however, Lyman gave Ned a punch in the ribs with an elbow and nodded toward the ground. His wrists were fast in the harness so he could not use his hands. Ned looked down and instantly dropped the Nelson a few hundred feet.

Some distance down the Madeira, in the center of the stream, were the lights of a boat which seemed to be anchored there. Ned swept closer and tried his best to make out the outlines of the craft, but he could not do it without descending close to the river, and this he did not care to do.

"It looks like the Black Bear," he thought, as he shot up into the air again, "but of coarse it can't be. Those Boy Scouts are not fools enough to bring her up into this country."

So he came to the protection of the mountains and proceeded south toward Asuncion at a speed which caused Lyman to gasp for breath. Of course he was ignorant of the fact that Frank, Jack, and Harry had started out, during his absence, to explore the headwaters of the Amazon, hoping to come upon the Nelson before returning.

As for the lads on the Black Bear, they did not even know that the Nelson was so close to them that night. It was three nights later that they first saw the aeroplane drifting above them. Asuncion does not at all compare in beauty or in thrift with the other capital cities of South America. The government of the republic is so unstable that business men are loath to make heavy investments there.

For one thing the town is poorly lighted, and when Ned came, in view of the place at five O'clock the few street lamps were already out. People were abroad at that early hour, however, and small crowds soon gathered on the street corners to watch the great airship approach.