The sun was hardly an hour high the following morning before all was in readiness for the start. In fact, the party waited only to despatch breakfast and make a last thorough inspection of the flying auto. All other details had been attended to the night before.

Hearty good-byes were said to Judkins, who had proved himself a decent sort of fellow, and who had had but little part in the schemes of the rascally crew of the Valkyrie. This done, the party got on board and the lines were cast off.

It had been decided to follow the river for some distance further, as the professor and Captain Sprowl had an idea that it might prove to be an arm of one of the larger tributaries of the Amazon. At five-thirty that morning Jack set the propeller in motion and the machine glided off up the river without a hitch.

With rapidly throbbing engines she negotiated bend after bend, and at last reached a spot where the stream appeared to be growing rapidly narrower. As a consequence of this, the current increased in velocity till navigation was difficult.

“This won’t do,” declared Jack, glancing at his instruments; “we have only made fifteen miles in the last hour. If you are agreeable we will go up now. We’ve come as far as we can profitably go on this stream.”

They all agreed with him, and presently a hissing sound told that gas was rushing into the big bag, inflating it for flight. Tom adjusted the hydroplanes to a position fit for aerial use, for they had found that, except on rough water, the Wondership would float as well without her hydroplanes as with them. This was doubtless due to her broad beam and general boat-like proportions.

In the midst of their preparations, or rather just as the Wondership was ready to take wing, there was a rustling sound in the bushes, and without warning a score of savage forms burst through the jungle. It was evident at a glance that they formed a portion of a hunting party, for some of them carried the carcass of a deer. The others, coppery-colored specimens, carried bows, long slender spears and another weapon that looked as if it was formed out of a long tube of bamboo.

For an instant they appeared as much astonished at the sight of the adventurers as the white men were at their sudden apparitions. They stood stock still, staring at the huge swelling gas-bag, the gleaming metal car of the Wondership and the occupants of the craft, as if they had been graven out of stone. This afforded a good opportunity for the astonished party to survey these children of the forest.

Some of them, leaders or head men, apparently, wore ornaments, collars and waist bands decorated with macaw feathers and bits of bone. Others were attired simply in sandals made of bark, and wore a sort of loin cloth made of snake skin. Their hair was thick, fairly long and inky black, their skins, as has been said, of a coppery hue. As to their general build, they were decidedly undersized, almost dwarfs, judged by Caucasian standards. They were, in fact, a hunting party of the war-like Tupi-Guaranian race which roams the forests of Brazil.

All at once, and without giving the party of travelers any opportunity for parley, several of the Indians raised the long pipes to their lips and a rain of tiny darts came about those in the craft. One of these darts struck Dick in the hand and inflicted a painful wound.

“Up, get up! Those blow pipe things may be poisoned!” cried Captain Sprowl.

He snatched up a rifle and in a minute some of the Indians would have paid the penalty of their attack, but that Mr. Chadwick caught the irate mariner’s arm.

“Don’t shoot. They know no better,” he exclaimed.

“Then they ought to be taught,” grunted the angry captain. “Look there, will you? That’s all the harm they mean!”

As he spoke, the Indians retired behind the trees and began to pour in a rain of arrows.

But luckily, Tom and the rest had by this time recovered their wits. The metal panels used to make the Wondership a water-tight craft were slid into place and locked, making the craft a cigar-shaped stronghold which no arrow could pierce.

In the sides of the rounded panels were portholes of thick glass through which they could witness the amazement of the Indians at this move. The darts and arrows, and now and then a spear, pattered and rattled against the metal like hail, but for all the damage they did they might as well not have been thrown. The tough metal turned their points like armored steel.

“Talk about bein’ snug!” cried the skipper admiringly. “Why this craft could go any place without gettin’ harmed.”

“We meant these panels to keep out water in rough weather,” said Jack, “but they do just as well as a protection against Indians. I never thought they’d be put to this use, though.”

“All ready to go up,” he said presently.

“Then let her go!” cried Mr. Chadwick.

The great craft quivered and swayed and then rose straight up from the river while the astonished Indians yelled and then threw themselves on their faces in terror. Up like a bullet from a rifle the graceful craft shot, until it was soaring high above the tree tops. Then the panels were slid back and the passenger part of the machine was once more open to the air.

They looked down at the Indians. Dwarfed to mere specks they could see the Tupi-Guaranians gazing upward and shooting their bows and arrows and their blow-pipes,—the latter form of weapon believed to be peculiar to the Amazonian tribes.

“Well, that shows us what sort of a reception the Indians of this country are inclined to give us,” commented Mr. Chadwick.

“But consarn the pesky skunks, I reckon that this sky clipper can give ‘em all the go-by if it comes to that,” declared Captain Sprowl belligerently. “That way you boys have of turning it into a fort is certainly the greatest wrinkle I’ve struck in a long time.”

“And it’s a use for those panels of which we never dreamed,” cried Tom with enthusiasm.

“What’s the matter?” he asked the next minute, as Jack struggled with the steering wheel.

“I don’t know, the rudder appears to be jammed. Climb out astern there and take a look, will you? Or let Dick do it, he’s sitting behind.”

But Dick was having his hand bandaged, so the task fell to Tom. The young reporter’s dart wound was hurting considerably, and as a precaution against poison Mr. Chadwick, before he dressed the inflamed place, had ordered the boy to suck it so as to extract what poison was in it, in case the dart had been “doctored.” As an additional precaution he tied the boy’s arm above the wound with a handkerchief, twisting it till circulation was cut off.

Tom lifted the movable seat and made his way back to where the rudder frames and braces extended behind the craft like the tail of a bird. He leaned over to ascertain the cause of the trouble Jack had complained about.

As he shoved his face over the back of the craft, something whizzed viciously past his ear, and with a yell Tom tumbled backward, almost on top of Mr. Chadwick.

“What’s up?” exclaimed Dick.

“Th-th-there’s a man out there!” stuttered the astonished Tom. “He’s clinging to the rudder. It’s one of those Indians and he threw a spear at me!”

“Gracious! He must have climbed on to attack us before we went up!” cried Jack.

“Get him inside the ship,” said Mr. Chadwick. “He’ll be killed if he lets go!”

“Let somebody else get him in,” declared Tom. “He nearly took my head off with that spear. It’s not my fault he didn’t, either.”