"There's your star!" he shouted to Jack.

"Quick!" Harry cried. "Wigwag with that light. It is the Nelson!

They may be able to see us!"

"Yell, every soul of you!" directed Frank. "Yell! She is going away!"

The boys waved their lights frantically and shouted at the top of their voices, but the light in the sky crept away to the west and soon disappeared, evidently pa.s.sing above the clouds which lay like a black blanket over the Brazilian forests.

"Great heavens!" Jack sighed. "If we could only have made them hear! I'll bet they've been to Paraguay and released Lyman. Now they're going back home! Fine show we now stand of having any fun with them!"

"They went west," Harry corrected. "That isn't the way home!"

"I'd like to know just what success they have had," Jack went on.

"Say," he continued, "can't we do something to attract their attention? Why not set fire to some big dry tree and let her blaze up?"

"I just can't have it this way!" Harry said. "I can't stand it to have them come so close to us and then go away without knowing we are here. We've got to bring them down in some way."

"But they've gone!" Frank declared, gravely.

"If we make a big blaze," Jack hastened to say, "the reflection on the clouds will attract their attention, and they'll come back.

They won't be able to see the fire itself, of course, but they'll see the reflection, and that will bring them down to investigate.

Then we'll fire our revolvers and wigwag with blazing sticks until they see who we are."

"It may not be the Nelson," Harry suggested.

"I don't believe there's any other aeroplane sailing about the roof of the world," Frank replied. "Of course it is the Nelson!"

"Perhaps the Nelson was followed," Harry went on. "I've heard of such things. The chap in that machine may be looking for Ned.

Anyway," he added, "it won't do any harm to let the aviator, whoever he is, know that we are here. Come on, let's go ash.o.r.e and build a big fire."

"I certainly would give a year's growth to know whether that is the Nelson," Harry said, as the boys sought the sh.o.r.e and began gathering dry wood, which, it may be well to add, was not easy to find, as there had been quite a shower during the day. "For all we know," he continued, "there may be another aeroplane here. If the people who are trying for the Lyman concession are as active here as they seem to have been in Paraguay, they may have half a dozen airships out after the Nelson."

Finally a quant.i.ty of wood which was fairly dry was secured, and Jack bundled it up against a dead tree which seemed to run straight up into the sky until it touched the clouds. But when the boys came to apply matches they discovered that the wood was not dry enough to be ignited in that way.

"I'll get a gallon of gasoline and pour over it," Frank explained.

"Then we can run like blazes when we touch her off. What?"

The gasoline was brought, and the blaze started with a mighty concussion of the air. A portion of the highly inflammable fluid had entered a great crevice in the dead tree, with the result that there was an explosion which resounded through the forests for miles. Then the flames mounted the tree, which was soon blazing like a great torch.

"I guess that will attract their attention!" Jack said, shielding his face from the intense heat.

"Yes," Frank replied, "and I'm afraid it will attract the attention of others, too. You know we were told to sneak through this country like little mice!"

"It is too late now!" Jack said, a shadow of anxiety coming over his face. "We are in for it, I guess. What shall we do?"

Above the crackling of the flames, above the drawing and sighing of the wind, there now came a strange sound which seemed to proceed from the fire-tinted clouds above. Now and then branches of the nearby trees stirred mysteriously, and at times a wild shriek rose above the monotonous chattering.

"Monkeys!" cried Jack. "They've come out to help us bring the airship to earth. Good little beasts!"

"Don't be in too much of a hurry to give the little devils a certificate of good character!" Harry answered. "They may make trouble for us."

After a time the foolish, wrinkled faces of the monkeys were seen peering from trees. Then, above the din they made, above the crackling of the fire, constantly mounting higher, came a scream almost like that of a child.

"That's a jaguar!" Harry declared, "a South American tiger, and we'd better be getting toward the boat."

"The animals won't come near the fire," Frank said. "We may as well remain here and see the menagerie."

Directly it seemed to the excited lads that all the wild animals in South America were a.s.sembled about their signal. Harry declared that he heard the call of the red wolf, the scream of the tiger cat, the wail of the puma, the vicious snarling of the wild dog.

While the boys listened to the chorus their efforts to attract the attention of the aeroplane had produced, there came into the discord another sound--the hissing of a monster serpent. Heretofore the boys had little to do with Brazilian forms of animal life, for they had kept near the middle of the main stream of the Amazon, and also about in the center of the Madeira and the much smaller Beni, which was only a creek when compared with the other rivers.

Occasionally they had seen a monster cayman nosing against the current, and at times their progress had been r.e.t.a.r.ded by turtles, but they had never before seen anything like this. Their fire had certainly brought out a combination in nature which would have been decidedly interesting if it hadn't been so threatening.

"Me for the boat!" Jack said, with a shiver, as the serpent launched his head and a third of his body from the tree and swept about in widening circles. "I never could endure snakes!"

"I'm going to take a shot at it," Frank said. "I'd like to see him take a tumble into the fire."

"Better let him alone," Harry advised.

Frank was about to fire when Jack caught his arm and held up his hand in a listening att.i.tude.

"What is it?" Frank asked.

"Human voices!" was the quick reply.

"Inhuman voices, I should say," Harry observed, after a second of silence.

A chant unlike anything the boys had ever heard before undulated through the forest. It rose and fell with the gusts of wind, and always nearer to the fire.

"This is a new one on me!" Jack cried. "It is also another reason for getting to the boat! Come on, fellows!"

"I'm not going to run until I find out what that is," insisted Frank. "I'm going to write a newspaper story about this menagerie!"

"If you want your story published in this world," Jack cried, "you'd better get under cover, for that's the chant of the head hunters!"

"Wow!" cried Frank, and he beat both his chums to the boat.

"I guess we've started something!" Jack said, as he busied himself putting up the few panels which had been removed when they went ash.o.r.e. "Now, some one push that b.u.t.ton, and I'll get the Black Bear out of this creek. A good old scout like the Black Bear has no business a.s.sociating with the wild animals on sh.o.r.e."

"Right you are!" shouted Harry, and the propellers began moving.

Still, the boat made no progress to the rear, the reverse being on.

"What's doing?" demanded Jack. "You'd better hurry, for the head hunters are coming right along. See that big chief over there?

He's got a club that would level the Singer building at a blow!"

"I can't make her back," Harry complained. "There's something the matter below her in the stream. It was all clear when we came in."

In an instant all was intense excitement on board the motor boat.