Chapter XV. The Warning from the Sky
 

There was a shock when the prow of the Black Bear struck a canoe which lay full in its path. The momentum was retarded for only a second. Then the motor boat was beyond the line of war canoes with their screaming, gesticulating occupants.

Looking out of the rear ventilator, Frank saw a smashed canoe running down with the current, with a dozen or more natives clinging to it. But there was still a large number of canoes up the river, and the Black Bear was struck more than once by forceless bullets and poisoned arrows as she sped past them.

Armed with modern rifles, the Indians would have made short work of the occupants of the Black Bear, but the muskets they used were old and mostly out of condition. The arrows were far more deadly, although they stood less chance of penetrating the tough panels.

"Now," Harry said, as they passed a racing fleet of Indian boats, "we can open up a little and get a breath of fresh air! I'm just about suffocated!"

"Not just yet," Jack, who was at the front, said, "for there's a mess of the black scamps just ahead. They are on the bank, both banks, and seem to be waiting for something to happen. I wonder what it can be?"

"Some trap, I suppose," Harry gritted. "Well, all we can do is to ran on through them, if they come out in boats, and get out of their reach. We ought to be able to be out of this blasted country in a couple of hours."

"That's all right," Jack replied, "but you just listen a moment."

But the racing motors shut out all individual sounds, and Harry shut them down for a minute. Seeing this, Jack dropped an anchor at the prow, and the boat lay pulling at the cable in the current.

"What did you do that for?" asked Frank, addressing both boys from the stem.

"Listen!" commanded Jack.

"Look!" ordered Harry.

What Frank heard was the heavy, continuous roar of a waterfall. What he saw, as he crowded up under the plate glass panel in the top, were the lights of an airship!

"I tell you," Harry cried, excitedly, "that that's the Nelson. You can't fool me about that."

"Why doesn't she come down, then?" demanded Jack.

"Because she doesn't know that this is the Black Bear. That is an easy one! If she did she'd be here in a second."

The boys studied the lights a moment and then turned their attention to the Indians, who were now making a great clamor. In a short time it was easy to see what they were up to.

Above roared the falls and the rapids. At this point in the Beni river there is a swift drop from the mountain plateau above. It will be remembered that the Beni reaches away up into the Illimani mountains, with its springs not far distant from the summit of the Andes.

Where the boys were the Paredon and the Paderneira, falls and the Araras and the Misericordia rapids made the navigation of the river, even in the protected Black Bear, impossible for many miles. The Indians seemed to understand this, for they had gathered at the foot of the falls, possibly expecting to see the craft attempt the ascent.

Jack watched them from the prow for a time and then asked:

"What's that they are throwing into the river?"

"Logs!" replied Harry, looking out over Jack's shoulder, "and brush!"

"Well, of all the--"

The sentence was not finished. Frank, at the stern, gave a yell and fired out of the loophole. "Come here!" he shouted, then, "if you want to see what the devils are doing. This takes the cake!"

A glance showed the others what the plot against them was. Harry went to his locker for his revolver and Jack drew his from a pocket.

"I guess it is a fight now!" Frank said. "You see what they are doing?"

"Of course. Anybody can see that."

Jack reached out of the opening and fired a perfect volley down stream. Frank crowded against him to look out.

"Never touched them!" he cried.

"No," Jack went on, "they're forming a bridge with their canoes and running logs and brush down against it. They've got an obstruction already that the Black Bear never can get through."

"What's the matter with dynamite?" asked Harry.

"Oh, we can use dynamite as long as we have it," was the reply, "but there will be Indians on guard there long after we are out of the stuff."

"I guess that's right!" with a sober drawing of the lips.

"I'll tell you what we've got to do," Harry said, presently. "We've got to put on full power and try to run up the rapids."

"Why, there is noise enough for a ten-foot fall," Frank replied.

"We've got to risk it," Jack went on.

"Now, you just wait," Frank cut in. "I don't think you've got this thing sized up right at all. Harry," he continued, "who does this boat belong to?"

"To the Black Bear Patrol," was the reply. "You know that well enough."

"Then we can do what we please with it, so long as we make it right with the other members of the Patrol?"

"Why, of course."

Jack looked at his chums with a grin.

"What are you figuring on?" he asked. "One would think you were planning to blow the Black Bear into smithereens."

"That's about it," Frank replied.

"And go to kingdom come with her?" laughed Jack. "Not any of that for me. I'm headed, eventually, for little old N.Y."

"I'm tired of fooling with these cannibals," Frank explained. "We haven't molested them, and yet they are after our scalps. They'll get them, too, if something isn't done--and done right away, at that."

"I'm with you!" Jack exclaimed. "I'm willing to try anything once. Only let me in on the secret!" he added, chuckling.

"You had it right," Frank said. "What I propose is to blow the Black Bear into smithereens, and about a thousand of those bloodthirsty natives with it. The world will be all the better for their being out of it. They are worse than the savage beasts in the forests."

"But what is to become of us?" asked Harry.

Frank pointed to the Wolf, tugging at the cable which held her nose to the stem of the Black Bear.

"We'll be safe in there when the explosion takes place," he said.

Jack clapped the speaker on the shoulder.

"You're all right!" he cried.

Harry looked mystified for a moment, and then said, speaking loudly in order that his voice might be heard above the shouts of the savages and the beating of arrows against the panels of the boat:

"It looks as if we'd have to do it. I hate to leave the Black Bear in such a mess away off here in South America, but I don't see how we are to get her out. The Wolf will carry us all right, I suppose?" he said, tentatively.

"Sure thing!" Frank replied. "I've been thinking it all out. We'll do it this way: When we get ready we'll put on full speed ahead on the motors, with the prow turned against that obstruction below. Then we'll hop into the Wolf and shut everything down tight. The Black Bear will weaken the jam below, and the sharp nose of the Wolf will poke through the rest of the logs and canoes. And there you are!"

"Free of the natives, and bobbing down the, river in safety!" cried Jack. "That looks good to me!"

"But about the dynamite?" asked Harry.

"Well," Frank replied, "we've got to use the Black Bear for a battering ram anyway, and she'll be all smashed up, so we may as well go the whole hog with her. We'll put a lot of dynamite down under the motors and fix a cap so it will blow up when the concussion comes. By that time the natives will be swarming around her, and they'll get what's coming to them."

"And where will we be when the explosion is rocking this half of the world?" demanded Harry. "Up in the air?"

"We'll be a cuddled up in the Wolf, between the lockers, with plenty of grub and ammunition, sailing down the river in a bullet-proof vessel. This move will burst up our meeting with the Nelson, of course, but there is no other way. They'll get us if we remain here."

While this talk had been going on, the cannibals had drawn nearer to the Black Bear, pressing forward from both banks in canoes and pounding at the panels with their arrows. It seemed only a question of time when they would board the craft and force the panels. Their shouts of victory were shrill and exasperating.

"You see how it is," Frank said, "the Black Bear can never be pushed up over the falls, and we can never get her past the obstructions below, even by the use of dynamite. If we could blow the those logs out of the way, the Indians would board us instantly. We could give them only a charge or two of dynamite and a few shots before they would be inside. Now' we can drift down the river in the Wolf without fear of entertaining man-eaters on board. They may get on top of the boat, but they can never get inside."

"And so we'll have to give up our trip!" wailed Harry. "We'll have to drift down stream in that hot hole and take a steamer at the nearest river town!"

"It strikes me," Frank observed, "that it is a mighty good thing we've got that hot hole to drift down stream in. If the Black Bear had only been constructed on the principle of the Wolf, we'd be in a position to give these heathens the laugh. Well, let us pull the Wolf up and throw out stuff enough to give us room. Then we'll get out the dynamite."

The boys drew the Wolf up by the cable as Frank tried to elude the watchful eyes of the savages long enough to open the hatch on top and climb inside, but a dozen arrows whizzed by his head when he looked out.

"Can't do it!" he said.

"Never in the world!" Jack assented.

"Another good scheme gone wrong!" Harry ejaculated. "What next?"

"Dynamite," almost shouted Jack. "We'll give them dynamite as long as it lasts, and then ram the logs below."

"We may kill, a couple of hundred," Frank said, "but it seems to me that there will be about ten thousand left."

The boys were indeed in a tight box. With their automatics and their dynamite they might keep the natives at bay for a time, but in the end they would be obliged to surrender or starve to death.

"Well," Jack said, grimly, "let's get out the dynamite. I want to see some of these devils blown up!"

Just then an arrow struck the plate glass panel at the top of the Black Bear's deck covering and Jack looked up. He gazed a moment in wonder and then let out a shout that rose above the yelling of the savages and the pounding of arrows against the panels of the Black Bear.

"Glory be!" he shouted.

Frank and Harry crowded to his side and looked up.

"It is the Nelson!" Harry exclaimed.

"You bet it is!" Frank admitted.

"Good old Ned!" Jack roared.

The aeroplane was only a few yards above the Black Bear. Already the natives were slinking away in their canoes. Those on the banks were slowly withdrawing into the shelter of the forests.

"They're running away!" Jack cried. "Now we'll have some fun with good old Ned Nestor!"

For a moment it looked as if the statement was correct; as if the natives, alarmed at the sight of the aeroplane would disappear from sight without a fight. But this supposition was soon disproved.

As the Nelson came nearer, a dozen bullets from the forests struck her planes. The boys, in the boat raised the panel and shouted to the aviator to look out for poisoned arrows.

Then the aeroplane shot up again. They could see that there was only one person on the machine, and that he was busy arranging something which looked like a stick of dynamite which he held in his hands.

In a moment something grim and sinister whirled and hissed through the air, and then there came a terrific explosion in the forest to the right. Trees were leveled, and a great hole showed in the bank. In an instant, following close on the roar of the dynamite, there came a chorus of cries from savage throats-cries of fear, of terror, of rage--and then silence.

For a moment it seemed as if the forests held no forms of animal life, then the sharp call of the tiger-cat, the wail of the puma, the chattering of the monkeys, came to the ears of the listening boys.

"I guess this coming act will consist of a feed for the wild beasts!" Jack said.

For a long time there was no sound of savage life in the forests, save that from the throats of beasts of prey, scenting blood and slowly drawing closer to the river's banks. The boys on the Black Bear looked into each other's faces and wondered.

"They didn't act that way when we exploded dynamite!" Jack said.

"No. They came right back at us!" Frank replied.

"I take it that they think there's something supernatural in this dropping of dynamite from the sky," Harry observed. "Anyway, they seem to have taken themselves off, and we'll open up and signal to the Nelson! Say, won't it be fine to see good old Ned Nestor again? I wonder how he knew we were here?"

"And I wonder where Jimmie and Leroy are?" Harry reflected. "There is only one person on the machine, and that must be Ned."

Jack was about to throw open the top panels when he caught sight of the aeroplane again, nearer to the water than before.

"What's Ned doing?" he asked, pointing upward.

"Talking!" exclaimed Frank.

"Wigwagging!" Harry broke out. "Now, let us see what he says."

Slowly to the right and left, up and down, an electric bulb flashed in the sky. Harry counted.

"That's C;" he said, "and that's 'a,' and that's 'u,' and that's 't,' and now 'i,' and 'o,' and 'n.' 'Caution!' That means that we've got to stand pat for a time yet."

"It also means," Jack said, "that we've made no mistake about that being the Nelson, with a Boy Scout on board. Those wigwag signals show the supposition to be true."

"Well," Harry puzzled, "he wouldn't be sending us a warning from the sky if there wasn't some danger we were not aware of. There is something going on that we are not wise to."

There was a short silence on board and then Frank remarked:

"We must be nearer the falls than we thought, for the water seems to be a ripple about us. Rear it! I'm going to look out and see it looks like."

In a moment he was jamming the panel shut and springing the slides over the loopholes and the ventilators.

Jack sprang to the prow, not knowing what danger threatened, but obeying the sudden gestures of his chum to close every opening. Before he sprung the steel panel over the ventilator he glanced out on the river.

"Great heavens!" he cried. "Get your guns, boys!"

The whole surface of the stream, as far as the boy's eyes reached, seemed covered with savage heads, floating, drifting, down upon the Black Bear.