The Boy Inventor's Wireless Triumph

Leaving the Tarantula to drift at her sweet will, all haste was made by the youthful adventurers in regaining the side of the Sea King. When they reascended to the deck of that craft, after making fast the Vagrant, they found a newcomer among the crew to greet them,—namely, MacDuffy, the engineer, who announced that he had made temporary repairs.

“But they willna be lastin’ lang, I’m thinkin’,” he said ruefully, “I dinna ken if they will carry us a hundred miles.”

“And it’s a good three hundred or more back to that river mouth,” cried Ned in dismay.

“Aye, lad, it wull be all of that,” agreed the Scotchman.

A sudden idea struck Jack.

“Is there any one on board who understands wireless besides Ned Bangs?” he asked abruptly.

Sam Serviss, a youngish-looking seaman,—he was third officer of the Sea King,—stepped forward.

“I can read Morse and Continental,” he said simply, “and I’ve taken lessons from Ned Bangs here. I guess at a pinch I could operate a wireless all right.”

“Good. That puts my plan on a feasible basis,” exclaimed Jack.

“What may the plan be?” asked Captain Andrews interestedly.

“Just this: The Sea King will proceed to Lone Island, navigated by Mr. Serviss here. On the island, as you know, is a wireless plant. The generator is not a very powerful one, but you can harness the island apparatus to the generators of the Sea King, and obtain as much current as you want,—two kilowatts if necessary. I have a plan to increase the power of the Vagrant’s outfit, so that we can keep in touch with you.”

Captain Andrews and MacDuffy nodded. Jack went on, while they all listened with deep attention.

“The Sea King carries a gasolene launch. On arrival at Lone Island you can try to get into communication with us. In the meantime the launch can be despatched to Galveston for the supplies and tools needful to mend that shaft properly. This being done, Mr. Serviss will watch the wireless for further instructions, or, in case of need, proceed to our rescue.”

“Then you mean to go back to Yucatan the noo?” inquired MacDuffy.

“Of course,” rejoined Jack, quick as a flash, and in a tone that showed he had indeed arrived at a definite conclusion in the matter. “It’s my duty and Tom’s to rescue our relatives, and that as soon as possible.”

“And you’ll no be countin’ on taking me?” asked MacDuffy, rather piteously.

Jack shook his head.

“The capacity of the Vagrant is limited, Mr. MacDuffy,” he said, “and we may have to adopt another means of transportation before we get through—I mean the aero-auto.”

“Good. The very thing,” was Ned’s enthusiastic comment.

“I guess Captain Andrews, Tom, Ned, Jupe and myself will be a big enough force to take along,” went on Jack; “of course, we’ll carry the gas-guns and a supply of ordinary firearms and ammunition.”

The boy’s plans were so clear and well-defined that there was no opposition. By this time the sky was streaked with gray and rose color in the east, and a wan light overspread the sea. It showed them the faint and distant outlines of the Tarantula, drifting seaward in the clutch of some strong ocean current. Evidently, then, they had nothing to fear from that source.

The work of hoisting the aero-auto from its well on the Sea King, and transferring the odd land-and-air traveler to the Vagrant was set about at once. Blocks and tackles were reeved on the derrick boom of the after mast of the Sea King, and with wondrously little effort, the vehicle the Boy Inventors had evolved was transferred to the flush after deck of the Vagrant, where it was lashed in place, the ropes that bound it being affixed to ringbolts on the deck.

The Flying Road Racer must be described in some detail here, as it is destined to figure largely in after events of the Boy Inventors’ lives. The auto part of the wonderful machine, then, was a cigar-shaped affair of aluminum, with four wheels of the “disc” type. It was fitted much like an ordinary auto, with padded seats in front and in the tonneau, equipped with shock absorbers, and was twelve feet in length.

In the front of the car the engine, a hundred horse-power, eight-cylinder, four-cycle machine, was installed. The controls led to the steering wheel, just as is the case in ordinary cars. The crank shaft, however, projected through the front of the car, and was provided with a slotted terminal, by means of which an eight-foot aerial propeller, carried in sections in the car itself, might be affixed at will.

Above the main body of the car was a light, but strong, framework supporting a balloon bag,—also cigar-shaped, and of the finest oiled silk,—of a capacity of about fifty thousand cubic feet of gas, and with a theoretical lifting power of forty-five hundred pounds. The method of inflating this bag at will, and thus converting the auto into a practicable dirigible, was the most startling innovation about the invention.

The body of the car, as has been said, was cylindrical, with sharp ends, like a mammoth perfecto cigar. This cylinder was divided in half, longitudinally, by a floor of aluminum alloy. The entire lower chamber thus formed was a big generating tank for a gas having a lifting capacity exceeding hydrogen vapor by a ratio of three to one. This gas was generated from brownish crystals formed of a compound of hydrogen-saturated alum and another chemical akin to radium, which the boys, for the present, kept a close secret.

Two pounds of these crystals, when forty gallons of water were added to them, formed close to sixty thousand cubic feet of the powerful inflation gas. One hundred pounds of the crystals were carried in a special compartment of the aero-auto, and constituted an ample supply for all emergencies. To inflate the bag, then, all that had to be done was to unbolt a metal hand-hole in the floor of the front section of the car. Through this the crystals were dumped into the tank beneath and the water added. The opening of the generator was then closed and clamped down tight, hermetically sealing the tank. The gas, under compression, was explosive, and was utilized to run the motor as well as for inflation purposes.

Immediately in front of the operator of the car was a gauge showing at all times the pressure in the tank, and when the gas bag was in operation the amount of gas in that also was indicated. When sufficient gas was generated, the operator turned a valve and the gas from the tank instantly began rushing into the bag carried on the framework above him. The bag was so folded that it inflated without necessitating much attention. Three broad bands of rubberized fabric of great strength encircled the gas bag proper.

To these were attached wires of a tensile strength exceeding anything hitherto known. The other ends of the wires, of course, were fastened to the body of the aero-auto, so that when the bag was sufficiently buoyant the entire car and its occupants were borne aloft. By means of an exhaust pump connected with the motor, the volume of gas could be reduced at will, causing the entire aero-auto to sink at the pleasure of those directing the machine.

“Astern” of this wonderful invention was a rudder of vulcanized silk and vanadium steel framework, which, when the invention was in use as a land vehicle, was folded. When it was desired to take the air the release of a simple clutch caused the rudder to assume its proper position. At the same time, two long planes could be attached to the sides of the car, to be used in ascending or descending. The machine had two steering and governing devices. One wheel was used for the auto control, and another “tiller” was put in use when it was soaring through the air. The control of the aerial rudder, planes and engine, all centered in this second wheel, thus putting the craft, at all times, under one man—or boy—management. In conclusion, it may be mentioned that the craft was equipped with speedometer, barometer, barograph and patent self-starting devices, doing away with the old-fashioned “cranking” of the engine. The wheels were fitted with semi-solid tires of great size and strength, and the shock-absorbers before mentioned obviated any danger of a severe jar or jounce on landing. The machine had been given several trials at High Towers and had been found to work perfectly.

It is not necessary here to give a description of the loading of the aero-auto, the leave takings, and the final instructions and messages that passed between the Vagrant and the Sea King. Suffice it to say, that at eight o’clock that morning all preparations on both sides were completed and that at eight-ten precisely the two vessels parted company. The Sea King steamed northward slowly, bound for Lone Island, and the Vagrant headed for the mouth of the river on which the plantations of the rascally Mexican were situated. At that time the Tarantula had drifted out of the adventurers’ ken altogether, over the eastern horizon.

Leaving Captain Andrews and Jupe in charge of the Vagrant, the lads, thoroughly exhausted now that the strain and care of the long night were over, sought their bunks and were soon wrapped in slumber. In their dreams they flew high above the plateaus and rugged ranges of the mysterious land for which they were bound, questing the unknown in search of the lost ones.

It was noon of the next day when Captain Andrews announced that they were still some two hundred miles from their destination. But, as the boys were all three of them busy over the aero-auto, adjusting and examining every part of the queer craft, the time flew swiftly. The dawn of the third day found them anchored off the jungle-clad coast, while not a mile from them the waves were breaking on the bar that marked the mouth of the shallow river, which, they subsequently learned, was called the Apak.

It would be two hours, so Captain Andrews calculated, before the tide turned and made the passage of the bar possible. In the meantime. Jack brought on deck the silver chest, which he had, of course, taken possession of, pending the time when he could deliver it to his father. The adventurers spread the three blazing gems it contained out on the deck, and revelled in the glow of light and wonderful inward fires the precious stones revealed as the bright sunlight played upon them.

The Vagrant had once been used as a passenger craft at Galveston, and her former owners had installed an iron safe in the cabin for the protection of valuables. In this receptacle Jack replaced the silver casket after they had examined the gems to their hearts content.

By this time Captain Andrews was ready to pronounce the crossing of the bar at the river mouth feasible. The tide had risen till the tempestuous breakers had subsided into long swells, with a narrow passage of smooth water marking the channel. Carefully following this, the skipper of the Sea King piloted the Vagrant through into the calm water of the estuary beyond.

The boys, grouped forward, gazing at the surroundings with eager eyes, beheld a scene full of wild, tropic beauty. The white beach, blazingly radiant in the strong light, was bordered by a dense jungle of dark, melancholy looking mangroves. Beyond these came a tangle of brilliantly green jungle, in which the broad fronds of the banana plant predominated, while here and there a tall palm reared its feathery head.

Further back still the foliage changed again. Lordly groves of mahogany trees, rosewood, and giant royal palms raised their crests. In the distant background, far withdrawn, the misty blue outlines of a range of majestic, rugged-looking mountains showed against the steely blue sky. They looked as if they were hundreds of miles off at least; but Captain Andrews explained that the distance from the shore to the foothills was not so considerable, by a great deal, as it looked. The condition of the atmosphere, laden with the moisture of the lowlands, lent them this appearance of tremendous remoteness.

“It is in those mountains,” said Captain Andrews, “that the remnants of the most ancient of the Maya tribes still live. They tell stories up the coast, in the civilized portions of Yucatan, about vast ruins and remains of splendid cities to be found back there.”

The boys gazed up at him as he stood at the wheel. A magic world of romance and adventure seemed suddenly opened before them by his words.

“I recall reading once,” said Tom, the studious, “that the Mayas were civilized long before the Aztecs or Toltecs, and that their knowledge of the building arts exceeded that of either of those races.”

“Sort of pioneer real-estate men,” chuckled Ned Bangs, who in moments when he was not oppressed by trouble, as he had been recently, possessed a whimsical vein of humor.

“Ho! ho! ho! ah reckon dat’s right, Marse Ned,” roared Jupe, opening his big lips and exposing his ivories.

“Has any one ever penetrated into their country?” went on Tom, addressing Captain Andrews.

“I guess your father went as far as anybody,” was the response, “and you know how far he got. I have heard that the remnants of the ancient tribes have a law, making it death for the man who dares to advance into their territory.”

“But the natives that caught you didn’t seem disposed to kill you,” objected Jack.

“Oh, those fellows; they are of the inferior coast tribes,” was the rejoinder. “The ancient races regarded them as dirt under their feet. I guess they don’t know any more about the interior of those mountains than we do.”

The current of the river, discolored and yellow from the recent earthquake back in the foothills, was so swift as they ascended that Captain Andrews found no opportunity for further talk. It required all his attention to keep the Vagrant’s bow pointed upstream. The river narrowed considerably after passing its mouth. Its turbid current rolled seaward between two low and densely wooded banks, not more than sixty feet apart.

“How far is it to the spot where that craft of Herrera’s was moored?” asked Jack, when he found an opportunity.

“Fully fifteen or twenty miles, I should say,” was the response, “and if we are making two miles an hour against this current we are doing well. This river runs mighty near as fast as the Lachine Rapids back home.”

“You’re not far out on that, Cap,” remarked the volatile Ned Bang’s, who had quite recovered his usual flow of spirits.

The lad had not as much at stake as Jack and Tom, and, moreover, he did not quite realize the seriousness of the undertaking before them to the same extent that they did.

Hour after hour they fought their way up the coffee-colored river. The character of the vegetation on the banks had begun to change by this time. Here and there stood a majestic clump of mahogany trees; but logwood, a valuable article of commerce in the dyeing industry, formed the major part of the growth. Once, as they rounded a bend, the flash of a lithe body was seen among the trees, as a beautifully spotted jaguar slunk away from the overhanging limb where it had been lying.

“Let’s try the gas-guns on the next one we see,” suggested Tom, and the lads hastened below and returned armed with the odd weapons.

An opportunity to use them soon presented itself. From a thick mass of brake there came a mighty squealing and grunting, as the Vagrant came slowly around one of the numerous bends in the stream. All at once several small, bristly animals, like miniature pigs, dashed out with a mighty commotion.

Three gas-guns flashed to three shoulders simultaneously. It was an odd and rather uncanny sight to behold an instant later, six little wild piggies lying with their toes turned up, “dead to the world,” as the slangy Ned Bangs put it.

The boys were keen for going ashore and gathering in the victims of the ammonium nitrate compound. But Captain Andrews vetoed the proposal as impossible.

“There’s hardly a foot of water in shore there,” he said, “it’s a case of ‘keep in de middle ob de road’ in this river.”

Dinner was eaten at one o’clock. Jack “spelling” Captain Andrews at the wheel while the skipper partook of a hearty meal, after which he indulged in a nap while Tom, in his turn, relieved Jack.

The latter was still below enjoying Jupe’s cookery, when there came a sudden hail from above:

“Say, Jack, hurry up on deck, won’t you? There’s something odd about the water just ahead of us.”

Ned it was who uttered the summons, poking his head down the companion way.

Jack finished his meal in a jiffy, and was on deck in another two seconds. He found the Vagrant’s nose still pointed up stream, but Tom, using the bridge controls, had slowed down the engines till the craft was almost stationary in the swift current.

Right ahead of them lay the cause of Jack’s abrupt summons to the deck.

A chain, composed of huge iron links, was stretched from bank to bank of the river, effectually barring further progress.

“Well,” said Jack, after a moment spent in surveying the obstruction, “we might have expected something like that. The question is, what are we going to do?”

“We might land and remove it,” hazarded Ned.

But Jack shook his head.

“Jupe, go below and call Captain Andrews,” he said, in as calm a voice as he could muster. “We won’t risk landing and trying to lower the chain for two reasons. One is, that Herrera, having been cunning enough to put up the barrier, is not likely to have left it unguarded. There may be hidden eyes watching us right now. The second reason is, that it has just occurred to me that a man who is playing the game he is, may have placed other more dangerous obstacles in our path.”

“For instance?” came from Tom.

“For instance,—mines.”

“By the holy poker! That’s so,” exclaimed Ned, “I guess we’d better turn back and make our advance by land.”

“Here’s Captain Andrews now,” struck in Tom, as the skipper of the Sea King came on deck, hastily adjusting his white pith helmet.

There was no need to tell that veteran seaman what had happened. He took in the situation at a glance.

“It would have been funny if we hadn’t run up against something like this,” he remarked, almost in Jack’s words.

“The point is,—what now?” said Tom.

Captain Andrews agreed with Jack that it would be a foolish risk to land and try to remove the chain.

“I’ve quite a notion that there are some rifles in that brush, all ready for use in case we try to proceed,” he said reflectively, “my advice is to drop back down stream and hold a council of war.”

All agreed that this did seem about the only thing to do under the circumstances, and accordingly Tom handed the wheel over to the sailor while he went below to “stand by” the engines.

In that muddy stream, with its sand banks and shoals, the maneuver they were going to try would call for some delicate seamanship and swift handling of the motor.

Captain Andrews, with his lips grimly compressed, grasped the wheel and sounded a signal. Slowly the Vagrant, which had been “hanging” motionless, began to drop back with the current.

“Too bad we can’t turn around,” complained Jack.

“Wouldn’t dare to chance it,” rejoined the captain, “for all we know there may be a sandbank on either side of us right now.”

A deathlike silence hung over the Vagrant as she drifted stern first down the river. The wheel spun swiftly this way and that under the helmsman’s muscular direction.

“She goes as well backward as she does forward,” Ned was beginning, when there came a sudden shock that almost threw them off their feet. Jupe, in fact, did fall sprawling on the bridge.

At almost precisely the same instant a shower of bullets whizzed above them, singing a sinister song as they screeched about the motor craft. Dense brush lined the banks, and the shooters were well concealed in it. Not even a puff of smoke betrayed their exact whereabouts.

And, while this hailstorm of lead whistled about the adventurers, they realized all too clearly that the Vagrant had run hard and fast on one of the very sandbanks the captain had dreaded. One thing, however, speedily became evident, and that was that the bullets had not harmed them, because they were not intended to—yet. The shower of lead was aimed high above their heads. Presently it ceased altogether.

“That was a warning,” decided Captain Andrews. “Boys, your folks are certainly surrounded by a barb-wire fence.”

The lads did not answer. But as they sensed the nature of the obstacles that were piling up in the way of their enterprise, a look of consternation came over their faces. “The Chadwick Relief Expedition,” as they had christened it, appeared to have run up against a stone wall.

“I guess we are not in any danger of another fusillade if we stay where we are, or keep on dropping back,” said Captain Andrews after an interval of thought, “but if we try to keep on going we’ve had a sample of what to expect.”

The boys could not but agree with him. At length Jack spoke.

“Hadn’t we better try to get the Vagrant off whatever we’ve struck?” he said. “I’ve got a plan in my head in that case; but I don’t think this is the healthiest place to discuss it.”

“We can put out a light anchor and try to warp off,” said Captain Andrews.

It was agreed to try this plan for rescuing the Vagrant from her uncomfortable berth. The dinghy was lowered and manned by Jack and Tom, who took with them the light anchor which was attached to two hundred feet of line. A hundred feet down stream they dropped the mud-hook, and then rowed back to the Vagrant.

When they were once more on board the winch was manned and, to their delight, as the rope tightened the Vagrant’s stern began to swing.

“Keep at it, lads,” cried Captain Andrews to the perspiring laborers, “if that anchor will only hold I believe we can get off.”

The anchor did hold, and after ten minutes more of back-breaking work the craft’s bow slid out of the mud bank with a sucking sound, and she was once more free. The anchor was hauled on board, and, without further mishap, the Vagrant was set once more on her down-stream course.

The first attempt of the courageous little band to rescue their comrades had met with a rather ignominious failure. Captain Andrews said as much that evening, as they found themselves anchored near the mouth of the river they had fruitlessly ascended with so much pains.

The skipper voiced this opinion after supper, while they sat on deck casting anxious eyes to seaward now and again, for the recollection of the Tarantula was strong upon them. Above all things, they dreaded the reappearance of that drab-colored craft.

“You said you had a plan, Jack,” said Tom, as the skipper disconsolately drew on his pipe, “Now’s the time to broach it. What is it?”

“Just this,” was the simple reply, “we’ve got the aero-auto. It looks as if the time had come to use her.”

“And leave the Vagrant here to be destroyed when Herrera happens along?” demanded Tom.

“That doesn’t follow. Did you notice that small creek almost overgrown with brush that branches off about a mile above here?”

“Yes, lad,” came from Captain Andrews, whose tones gave evidence of his intense interest, “you’re planning to hide the Vagrant there till we come back again?”

“You’ve caught my idea exactly,” said the lad. “What do you think of it?”

“That it’s a dumb-gasted good one, and that I, for one, am willing to risk my neck in that flying automobubble of yours any time you say the word.”

“Then I say it right now,” shot out Jack, with flashing eyes. “We can’t ascend this river by water; we’ll try the air route.”

It was while they were still buzzing with the enthusiasm that Jack’s fiery words had created that Tom uttered a sharp exclamation.

“Jupiter!” he exclaimed, pointing seaward. “Look yonder. We’re not playing a lone hand in this thing now.”

Some distance off apparently, but rushing across the water at a swift pace, was a bright white gleam,—the light of a vessel approaching the bar at top speed.

“The Tarantula, for all I’m worth!” exploded Captain Andrews. “Confound her, why couldn’t she have kept her hands off for twelve hours longer?”

Fortunately, there was no ray of light visible about the Vagrant. The incandescents had been switched off in every part of her, with the exception of the engine room. In this compartment Tom, by some inspiration, had closed the deadlights, and therefore not a gleam of light leaked out to betray the whereabouts of the craft.

“Do you think the Tarantula will cross the bar to-night?” asked Jack presently.

“I don’t imagine so,” was the rejoinder. “They wouldn’t be idiots enough to take such a chance as that on this tide. No, if you ask me, we’ve got the night ahead of us till the first streak of daylight.”

“Good enough,” said Jack, with much inward satisfaction; “and now, I’ve been thinking, it wouldn’t be a bad idea for me to keep watch by the wireless. It’s likely enough that Herrera will try to send a message to his plantation up the river, provided he’s managed to get his apparatus repaired.”

“I’ve been thinking that, too,” said Tom. “I’ll go below and start up the generator.”

“You might as well,” said Jack, “although I don’t think that we’ll send out any messages to-night. Our job is to catch what we can from the air.”

While Tom hastened to the engine-room to start up the dynamo. Jack made his way to the cabin, accompanied by Ned Bangs. Captain Andrews and Jupe remained on watch on deck.

Seating himself at the wireless table. Jack adjusted the head band, placed the receivers at his ears, and then threw the switch for receiving. Ned, in the meantime, had run up the wireless mast with its slender antennæ, or aerials.

This done, Ned rejoined his chum, seating himself beside him. After an interval he spoke.

“Anything yet?”

“No; silent as the grave. Suppose you go on deck and see what Captain Andrews and Jupe have observed.”

Ned was back from his errand in a short space of time. His face bore a well-pleased grin, as Jack could see in the light of the solitary incandescent which illumined the cabin, the shades having, of course, been drawn across the portholes before it was switched on.

“Well?” questioned Jack.

“Well,” echoed Ned, “everything is going famously. The light stopped moving outside the bar, and presently Captain Andrews heard the rattle of her anchor chains as she let go her mud-hooks. Everything has been quiet since.”

“Too quiet. I wish——”

Jack broke off suddenly, holding up a hand to Ned to command silence. Out of space the electric waves were beginning to break against the aerials above. The Tarantula was talking to some one on shore in a rapid stream of dots and dashes. Jack’s hand flew across the recording pad. As before, the paper was soon covered with figures—the code which Tom had exploded.

After half an hour, during which his hand had frequently sought the tuning apparatus. Jack’s labors ceased; but his face bore a radiant expression.

“The message had a lot in it about us, and my father and the rest,” he said. “They did not codify our names, but spelled them right out. That’s how I know. They——”

“Hadn’t you better listen in case there’s any more coming?” asked Ned.

“No; they’re through for to-night. They exchanged the good-bye signal. Now to find Tom and get him to translate this jumble of figures.”

But Tom, after expending a lot of fruitless labor on the papers, declared he could make nothing of them.

“Maybe they’ve changed the code, or maybe——”

“They’ve been using Spanish this time,” exclaimed Jack, struck by a happy inspiration.

“Cracky! I’ll bet that’s just what they have been doing,” cried Ned. “Say, fellows, you just copy out those messages while I get Captain Andrews below in two shakes of a duck’s tail.”

He bounded off up the companion way, while Tom busily transcribed. So fast did he work that he had a lot of words written out when the skipper appeared.

“So you’ve been catching something out of the air, have you?” he asked as he entered the cabin.

“Yes; and I guess it’s important, too,” declared Jack, “but you’ll have to translate Tom’s notes. Captain, because it’s all in Spanish.”

“That will be simple enough,” said Captain Andrews, sitting down and drawing toward him the scattered sheets which Tom had already rendered from the figures of the code.

The veteran seaman began stolidly to con over the Spanish words, not all of which, owing to Tom’s unfamiliarity with the language, were written in correct form. But before long his composed attitude gave way to excitement.

“Jove, lads!” he exclaimed, “this wireless is a wonderful thing. It’s tipped off that greaser’s hand to us in great shape. He——”

“Wait till you get the whole message and then you can read it out to us,” suggested Jack.

Both the sailor and Tom worked like beavers at their task, and ere long Captain Andrews leaned back in his chair and announced that he was ready to read the messages as he had translated them.

As he had hinted, they caused a sensation. Herrera had wirelessed his plantation, and after a short interval had received a reply. He,—or, rather, his operator,—then proceeded to relate all that had occurred; and told,—the boys had to smile at this,—how the accursed gringos had tricked them by some sort of hypnotism!

However, so the message ran on, the capable Senor Herrera had managed to rally his men on their recovery from the spell of witchcraft, and had speedily organized a force to repair the damaged machinery and wireless apparatus. This done, all speed had been made at once for the coast whither, as they guessed, the gringos had preceded them.

“Well, Herrera’s, man ashore soon informed them on board the Tarantula that such was the case,” continued Captain Andrews, “and gave him a full, true and particular account of how they stopped us with that chain and that fusillade. He told Herrera that he had confined the gringos in one of the buildings used for the hemp crushers, and that they were as safe as if they were in a safe deposit vault. Friend Herrera then congratulated him on his astuteness, and said that he would run the bar first thing in the morning, only stopping, by the way, to blow the Vagrant out of the water and send us all to Kingdom Come.”

“Reckon he’s got another guess coming on that,” grinned Ned Bangs, looking at Jack.

“I hope so,” said that lad; “but now that we are in possession of these facts it’s up to us to move quickly. Captain, do you think we can find that branch creek in the night?”

“We’ve got to,” was the grim response, “if we don’t want to part with the good old Vagrant, and I’d hate to lose any ship I’ve trod the deck of.”

“Then, let’s up anchor and get out of here,” said Jack.

“Intercepting that wireless,” he went on, “has taken one great load off my mind. We know that those we are in search of are safe, and we know, in addition, that they are confined in one of the hemp-making buildings.”

“And that’s a whole lot important to us right now,” supplemented Captain Andrews. “Whole campaigns have been won with less knowledge of the enemy’s country than we have.”

They went on deck. Outside the bar a light showed where the Tarantula lay at anchor. Herrera must have been chuckling to himself at that very instant. According to his knowledge of the situation, he had his foes completely “bottled up.” All that remained for him to do was to capture them and attain possession; of the coveted precious stones at his leisure.

While the Mexican was pondering such thoughts as these and nursing his revenge, the company of the Vagrant were busy,—very busy.

It was too risky a thing to chance making the noise that raising the anchor would have caused. So the cable was slashed and the engine started with the underwater exhaust in operation. Noiselessly the little craft glided up the stream and then turned her nose toward the bank. A break in the line of trees, showing against the star-sprinkled sky, gave the location of the creek mouth, and, feeling his way with the utmost caution, Captain Andrews drove his temporary command into it. It was driving, in a literal sense, for the brush and trees overhung the creek so densely that the Vagrant had to push her way among them. When she had proceeded about a hundred yards up the stream she was masked from the view of the river with complete effectiveness.

“Glory be!” sighed Jupe, in a voice of intense relief, when Captain Andrews ordered the second anchor “let go.”

“It will be safe enough to light up now, I guess,” announced Captain Andrews, when the anchorage had been accomplished. Jack had told him previously that they would need deck lights to work by when it was possible to use them without danger of detection.

When the incandescents on the after deck were switched on the boys at once fell to work on their “Flying Road Racer,” as Jack and Tom had christened the craft. There was much to be done, and they worked quickly. The tank was supplied with crystals and water, and the gauge before long showed a pressure which the lads knew was sufficient to inflate the bag when occasion arose.

This done. Jack determined to make a test of the engines. First, seeing that the neutral clutch was in working order, he pressed a button which set the self-starting apparatus,—run by electricity from a storage battery of great power and lightness,—into action. With a buzz and a whirr the machinery started, and bit by bit the lad speeded the motor up to its maximum number of revolutions per minute,—namely, two thousand. While the crank shafts whirled round he carefully examined the lubricating appliances. They worked as well as everything else, and fully satisfied with his test, the young inventor shut down the engine, with the announcement that so far as the machinery was concerned everything was in readiness for an immediate flight, or ground cruise.

While this had been going on, Jupe had been placing a stock of provisions on board, and Captain Andrews had assembled his navigating instruments and chronometers, which he had brought with him from the Sea King. By midnight Jack declared that it was time for the aero-auto’s passengers to get aboard.

A thrill of excitement ran through the whole party at these words; but Tom seemed suddenly to recollect something and stepped to Jack’s side, talking in a low voice.

The young leader nodded his assent to Tom’s proposal, whatever it was, and Tom vanished below, summoning Jupe to help him. When he returned, he had his arms full of mechanical apparatus, and the same was true of Jupe, who grunted under his burdens. All this impedimenta was placed in the tonneau, in lockers under the seats.

It now only remained to bolt on the aerial propeller, adjust the side-planes and fix the rudder. This was speedily done.

At twelve-thirty o’clock the party cast off the lashings which had bound the Flying Road Racer to the Vagrant’s deck. Jack climbed into the driver’s seat, taking his place at the aerial steering wheel. Tom sat beside him.

Captain Andrews, Ned Bangs and Jupe, whose eyes were almost popping out of his head, seated themselves in the broad, roomy tonneau.

The lights had already been switched off on I board the Vagrant and everything made snug. The silver casket, the gas-guns, the ammunition, and the other accessories from the Professor’s cabin which had not yet been opened, were, of course, on board the Flying Road Racer.

Jack bent forward and snapped a button switch. A hooded light above the various gauges and instruments on the dashboard shone out, shedding a soft but bright light on the appliances, but not striking up into the young leader’s eyes.

“All ready?” queried the lad, giving a backward glance.

“Ready as we ever will be, old top,” quoth the slangy Mr. Bangs.

“Let her go,” said Tom in a tense voice.

Jack’s pulses throbbed, and his heart beat a bit quicker than was comfortable as he turned the valve that admitted gas to the bag above them.

With a swishing sound, not unlike escaping steam, the folds of the great gas container began to fill out. It gradually assumed shape, swelling till it reached what appeared to be vast proportions. When Jack shut off the gas the huge, cigar-shaped balloon above them looked like an immense dark cloud, superimposed over their heads.

The bag took just fifteen minutes to inflate. During this time not a word was spoken on board the Flying Road Racer. The tension was far too great for speech.

As Jack shut off the gas a tremor ran all through the novel craft. She tugged and swayed at the single rope, reeved through a ringbolt, that still bound her to the deck. The suspension wires thrummed musically under the pressure.

“Let go!” yelled Jack suddenly.

Tom, who had been holding the end of the rope, dropped it. Instantly the Flying Road Racer gave a bound upward.

“Bust my toplights!” bellowed Captain Andrews in excitement at the novel sensation.

Jupe’s lips might have been seen to move. He appeared to be praying. Ned Bangs’ hands were clenched tightly. He was very pale.

“Look out for the tree tops!” cried Tom suddenly.

The wonderful craft, with her precious freight, swayed drunkenly toward the crests of a group of giant ceiba trees. For one instant disaster, at the very outset of their voyage, appeared inevitable.

But suddenly there was a whirring sound, like the drone of a monstrous night beetle. The engine was driving the propeller round at top speed.

Jack twisted the steering wheel over, and the Flying Road Racer, rising at the rate of a hundred feet a minute, shot clear of the menacing tree tops.

Up and up into the night she rose, while her occupants, forgetting their first alarm in their enthusiasm, gave a mighty cheer, careless, for the minute, of who might hear it.

The voyage of the Flying Road Racer had begun under a fortunate star indeed.

Directly the tree tops were cleared Jack set the planes at a rising angle, and the upward course of the Flying Road Racer was more rapid. She seemed fairly to shoot up into the ether.

“How do you like it?” asked Tom, turning his head-to speak to those in the tonneau.

“Ah’d like it better, Marse Tom, ef I didn’t feel I done lef’ mah insides behin’ me,” faltered Jupe.

“You’ll soon get over that feeling,” declared Tom confidently. “Just hark at that engine! She’s running as true as a human heart.”

“She is that,” agreed Jack, enthusiastically, “Tom, old boy, we’ve got the greatest land-and-air-craft ever put together.”

“And to think that you two lads, hardly more than schoolboys, invented her,” struck in Captain Andrews admiringly.

“I guess my father had a whole lot to do with it,” rejoined Jack modestly; “we could never have mastered a lot of knotty points without his aid.”

“Well, that doesn’t detract from what you’ve accomplished one bit,” declared Ned with enthusiasm. “This is the mode of traveling of the future all right.”

“We hope to make it so some day,” was Tom’s reply.

The night was almost windless, save for a slight puff now and then. But this didn’t bother the Flying Road Racer once she was under control, and Jack had managed to climb upward on an almost straight course.

Now he peered over the edge of the aluminum body. Beneath him he could see the gleam of the river in the starlight.

“We’ll follow the stream,” he decided. “It is bound to bring us to Herrera’s plantation.”

“Keep at a good height, though,” admonished Captain Andrews. “We know that those fellows have high-powered rifles.”

“We are now twenty-five hundred feet above the earth,” said Jack, glancing at the barograph. “We’ll go higher.”

He pulled a lever, setting the rising planes at a more acute angle. Up the aerial staircase they climbed, till the barograph’s indicator pointed to the figures five thousand.

Then Jack turned the prow of the craft in a westerly direction, while Tom, through night glasses, watched the earth so far below them, following the course of the river through the binoculars.

At forty miles an hour the Flying Road Racer swept through the air on her momentous errand.

When the Flying Road Racer took the air the weight that the craft carried was distributed as follows:

Aluminum body, wheels, motor, suspension wires, etc. 900 pounds.

Five passengers. (approx.) 800 pounds.

Provisions, water, etc. 250 pounds.

(The provisions included canned goods, preserved butter, tea and cocoa, flour, sugar, salt and a few delicacies.)

Radolite crystals, instruments, etc. 275 pounds.

Other articles,—including Ned’s last-minute contributions. 300 pounds.

Total 2,525 pounds.

This left lifting power to raise 2,475 lbs., which, however, could be increased to a considerable extent by utilizing the reserve sections of the gas bag.

Jack roughly estimated the combined weights of those they were to rescue,—his father, his uncle, Abner Jennings and the two sailors,—at a little over one thousand pounds. Thus, it will be seen, that there was no reason why the Flying Road Racer should not be able to perform all that was required of her, with some lifting power left over for emergencies.

The boy inventors’ craft had been in the air about an hour when Tom descried, far below them, the gleam of a light. In that wild country it was not likely to betoken anything else but the site of Herrera’s plantation houses.

They all agreed on this, and Jack, after a consultation with his comrades, decided that the time had come to descend. The plan they arrived at, after threshing the situation over in all its bearings, was to drop in the most suitable place they could find, adjacent to the plantation buildings.

Then the gas bag was to be reinflated, ready for emergencies, and two of the party were to reconnoiter the ground as carefully as possible. The remainder of the rescue was to be left to circumstances. At one hour and ten minutes after midnight. Jack started the exhaust engine up.

Instantly the Flying Road Racer began to drop downward through space with her planes set at a slight angle, as Jack did not want to coast to earth too rapidly. This course soon brought the craft above the summits of the forest trees, at a safe distance from the light they had perceived from aloft. To make assurance of being unnoticed doubly sure. Jack had shut off the motor. Silently as a night bird the great bulk of the flying auto settled earthward.

All this time their eyes had been strained to sight an open space in which they might land without risk of damaging the balloon bag. Tom was the first to see, through the night glasses, such an area of cleared land amid the forest.

It was a tract about ten acres in extent, and formed, as they surmised later, one of the outlying fields of Herrera’s plantation. It had not yet been put into cultivation, however, and afforded as fine a spot for an air craft to ground as could be imagined. Half an hour after the descent had begun the Flying Road Racer settled as lightly as a bit of breeze-blown down on earth once more.

Thanks to her shock absorbers, hardly a jar was felt by those on board as she landed with her bag half deflated and limp and wrinkled. No time was lost in alighting and throwing out the anchors, contrived by Jack, used for securing the craft to earth in case of a sudden wind springing up. These anchors differed considerably from the sea type of “mud hook.” They consisted, in fact, merely of discs of iron shaped like an inverted mushroom. One edge of the disc was driven into the ground, and the shape of the holding appliances was such that an upward tug merely served to force them more deeply into the earth.

The adventurers figured that they were about half a mile to the west of the spot where they had seen the light, which they believed marked the site of Herrera’s plantation houses. They also estimated that there were left to them about two hours and a half more of darkness. There was urgent necessity then for immediate action.

Much to the chagrin of Tom and Ned, but to the huge delight of Jupe, who had no great fancy for the work in hand. Jack and Captain Andrews were to be the ones to do the reconnoitering. Tom and Ned were ordered to stand by the Flying Road Racer and be ready for any sudden development that might occur.

While Captain Andrews and Jack were absent, it would be the others’ duty also to refill the gas bag, so that the aero-auto might be ready for an instant ascent in case of need.

These preparations completed, the two who were to assume the most risky part of the night’s work each selected a fully loaded gas-gun. In addition. Captain Andrews carried an automatic revolver; but it was on the former weapons that they would largely depend.

There remained nothing more but the leave-takings, and the fervent wishes for success in the daring enterprise, coming from the lads who were to be left behind. These final ceremonies being disposed of, the grizzled old sailor and his young companion set off. Tom and Ned watched them till the shadows of the forest swallowed them up.

By good fortune, the two, upon whom so much depended, struck a trail almost immediately after their first plunge into the blackness that prevailed under the tropical trees. The path had evidently been used by the laborers who had made the clearing beyond. It was a broad, well-defined track, and their progress was rapid and almost noiseless.

Neither of them spoke as they made their way along the path. The situation was too critical for words, and Jack crept along behind Captain Andrews, hardly daring to breathe.

He was on the tip-toe of excitement and anxiety, as was natural. At the end of the trail they were following’ lay either success or dire failure. There was no middle ground. In the event of their failing in their mission. Jack could not disguise from himself that the consequences would be awful indeed. He had come in contact with Herrera only once, but that single occasion had amply sufficed to show him the character of the man.

From time to time, as they advanced, they paused and listened intently. But, except for the drone of the night insects of the jungle, and the occasional scream of a nocturnal bird, there was no sound other than the sighing of the breeze in the tree tops far above.

There is no place more mysterious than the jungle at night. The dense thickets seem to the nervous traveler to hold all manner of hidden perils. Some of these are not altogether imaginary, either. The cunning, cruel jaguar, the huge serpents, and a score of other dangers lurk in the shadows.

Fortunately, neither of our friends was burdened with sensitive nerves, and it was well they were not, for their errand was not one for timid folk to embark upon.

They glided along after all these pauses, making as fast time as possible. All at once Captain Andrews, who was in the lead, as we know, stopped abruptly.

So abruptly, in fact, that Jack almost collided with him.

“What’s the——” began Jack.

But instantly the Captain clapped a hand over his mouth. He raised the other in a gesture that Jack read instantly: “Silence!”

Just ahead of them. Jack now perceived, the path broadened and emerged on a considerable clearing. The black outlines of several buildings, were scattered about this open space.

From one of them hung a lantern, shedding a yellow patch of light all about it. This, evidently, was the light they had seen from above.

As they stood, still as graven images in the protecting shadows of the forest, a stalwart figure, with a rifle over its shoulder, paced into the circle of light and then vanished again.

“A sentry!” huskily breathed Captain Andrews. “If we thought we’d catch them napping we’ve been badly mistaken.”