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Title: A Thousand Miles an Hour

Author: Herbert Strang

* A Project Gutenberg Australia eBook *

eBook No.: 0900851h.html

Language: English

Date first posted: October 2009

Date most recently updated: October 2009



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A Thousand Miles an Hour

by

Herbert Strang

ILLUSTRATED BY HOWARD K ELCOCK

CONTENTS



I.     IN THE AMAZON FOREST

II.    A NIGHT IN THE JUNGLE

III.   PAT HENEKY

IV.    JUAN COMES TO HEEL

V.     THE MINE

VI.    SEEING IS BELIEVING

VII.   LEVITY AND GRAVITY

VIII.  FIRST STEPS

IX.    MOLLENDO'S FIRST FLIGHT

X.     QUESTION AND ANSWER

XI.    THE TRIAL FLIGHT

XII.   WINGED

XIII.  THE RED MAN'S MERCY

XIV.   A RACE AGAINST TIME

XV.    TOUCH AND GO

XVI.   A SEA CHASE

XVII.  A LAST APPEAL

XVIII. THE GADFLY'S STING

XIX.   REVOLUTION

XX.    A PRESIDENTIAL RECEPTION

       CONCLUSION



IMAGES



THEY OPENED THE DOOR AND STEPPED ON TO THE GROUND

"YOU'VE GIVEN ME A MIGHTY DEAL OF TROUBLE."

THE STRANGE-LOOKING CONTRIVANCE ROSE STILL HIGHER

THE DANCE IN THE FOREST

THE GADFLY'S OCEAN FLIGHT

CHAPTER THE FIRST - IN THE AMAZON FOREST

DERRICK MOORE turned up his shirt sleeves, at every twist wringing drops of water from the thin material.

"A Turkish bath every day and all day is rather excessive, Pedro," he said.

His cousin smiled.

"You will get used to it," he said. "And the heat won't be so bad when we have left the river. Come and look at the map."

He lay flat on his face near a small tent, just capacious enough for two, and a canvas-backed map was outspread before him. Derrick flung himself down beside his cousin.

"We should be about here," said Pedro, placing his finger at a spot upon a wriggly black line-one of innumerable similar lines that formed a sort of network across the paper. There were few names printed on this part of the map; it showed little except the black lines indicating rivers and the conventional marks representing forests.

"Don't you think we ought to have taken this branch that comes in on the south?" said Derrick, pointing to a tributary a little east of their present position.

"Juan ought to know," Pedro replied. "He says he has been here before."

"Well, I hope he is right. The men are getting very sullen."

"It's their own fault we had to halve the rations."

"That doesn't make it any better. But it's rotten bad luck that we haven't shot anything for three days but a single peccary. Which reminds me: it's time we had something to eat, though I confess I've no appetite. It's too hot for anything."

Derrick got up, stretched himself, wrung more water from his shirt, and sat down on a rock at the door of the tent. Silently folding up the map, Pedro also rose to his feet, and called sharply, "Juan."

A small, thick-set, swarthy man appeared from among the bushes at the farther end of the clearing in which the tent stood. To him Pedro addressed a few words in Spanish. The man listened with a somewhat sullen air, then, without speaking, returned to the place he had come from.

"I don't like the fellow," said Derrick.

"I neither like him nor dislike him," responded Pedro. "He's useful; that's all."

The two lads sat in silence side by side, waiting for Juan to provide their evening meal. They were cousins, but there was no likeness between them except in their age. Both about eighteen, Derrick Moore was tall, lithe, of the fair Saxon type; Pedro Alvarez was several inches shorter, of a larger frame, and dark like his Bolivian father. His mother, Bertha Moore, had married the owner of a large mining property in the foothills of the Andes. The father was now dead, but the Señora Alvarez continued to live in the country of her adoption, and the mine was worked as in her husband's lifetime. Pedro had been educated in England, and had just completed a year's studies in a college of agriculture, that being the subject in which his main interest lay. A few months before the opening of our story it happened that some machine parts were needed at the mine which could only be obtained from England. Derrick Moore had had some training in engineering, and being an orphan without ties, he had welcomed an opportunity of visiting his Bolivian relatives, and had come out on the same vessel that brought his cousin and the new machinery. This had been transhipped at Para, and conveyed up the Amazon and its tributary the Madeira to San Antonio, beyond which steam navigation was impossible. There the boys had been met by Juan, a half-caste guide, and a crew of eight native Indians with four canoes. The journey up the winding tributaries of the Amazon had already occupied several weeks-weeks of monotonous paddling up the broad sluggish streams, diversified by frequent portages where the streams narrowed to rapids and cataracts.

It was at one of these rapids that an accident occurred. By what appeared to be mere clumsiness on the part of the crew of the canoe containing the machine parts and a considerable proportion of the provisions, that canoe had been drawn into the whirlpool at the foot of the rapids, swamped and broken to matchwood. Its cargo was lost, its crew barely escaped with their lives.

To Derrick the journey at first had had all the interest of novelty. Accustomed to boating on the upper reaches of the Thames, he was impressed by the contrast presented by this mighty Amazon, sometimes miles wide, its banks lined by huge forest trees, shrubs and creeping plants; the strange brilliant flowers, the bright-hued butterflies as large as birds, the tropical animals which hitherto he had known only in the pages of books or the cages of the Zoo. But for some days he had been feeling oppressed by the unvarying scenery, the constant steamy heat, the wearisome marches over sludge and slime when portages were necessary, the pestilent attentions of innumerable fierce insects which buzzed and stung from sunrise to sunset. Recent torrential rains had been the climax of discomfort. A new-born suspicion that Juan the guide was not so well acquainted with the country as he professed to be, together with signs of discontent and mutiny among the Indians, had bred in him a keen uneasy longing to reach his journey's end.

The little tent in which he spent the nights with Pedro had been pitched on a rocky bluff a few yards above the level of the river. Juan and the Indian crews were camped a short distance away. Below them the three canoes were moored to trees on the bank. On both sides stretched the forest-not such immense trees as Derrick had admired lower down, but trees which, though smaller, grew more closely together, and were thickly festooned with creepers and climbing plants. At this point the stream was about two hundred yards broad. The opposite bank also was densely wooded; whichever way he looked Derrick's eyes met nothing but sluggish muddy water, green vegetation dotted with bright spots of colour, and the heavy grey sky above.

While he and Pedro waited for their supper, a sudden jabbering broke out among the Indians beyond the bluff. Presently they came running up, their leader holding something in his outstretched hand. He halted in front of the two young men and began to pour out a torrent of shrill discordant cries, to Derrick incomprehensible.

"What does he say?" he asked.

Pedro sternly signed to the man to be silent.

"He says he and the rest are going no farther," said Pedro. "Juan has given him for supper no more than a handful of grain. He says they will starve if they go on."

"They will certainly starve if they go back," said Derrick. "Surely we are not very far from your hacienda now?"

"Unless Juan is quite at fault. I will tell them so."

He addressed the Indian in his own tongue. The response was another outburst.

"According to him," said Pedro, "Juan himself says that they ought to return. That's hardly credible. Where is the fellow?"

He called for Juan, and the man came up slowly.

The Indians grouped themselves about him, clamouring, gesticulating.

"Peace!" cried Pedro. "What is this I hear, Juan? The men say you advise them to go no farther."

The guide looked embarrassed. His eyes would not meet his employer's.

"They are hungry," he said. "I have little food to give them. How can I feed them? How can I prevent their grumbling?"

"We are all short of food," said Pedro, "through their carelessness in losing the fourth canoe. But we have not much farther to go. You engaged them for the journey; you must keep them in order. We have had bad luck in not sighting any animals or birds lately, but—"

He was interrupted by a sudden exclamation from one of the Indians, who stretched out his hand and began to dance up and down excitedly. Turning, Pedro saw an animal swimming from the opposite bank of the river, about a hundred yards away, its strange elongated snout just showing above the water.

"A tapir!" he cried. "Good meat, Derrick. Come along."

They dashed back into the tent and emerged with their sporting rifles.

By this time the tapir was already among the roots of the overhanging trees. Derrick took a shot at it. A violent splashing followed, but the animal disappeared.

"Follow us, Juan," said Pedro.

Making what haste they could, the three pushed along the bank of the river, stumbling over roots, forcing their way through the matted vegetation, sinking ankle-deep into the swampy soil, wrenching themselves from the clutches of creepers and thorns. The spot where the tapir had landed was indicated by the crushed plants and the water that had poured from its body; and Pedro, who had some experience in forest hunting, marked signs of the course it had taken.

"You hit it, Derrick," he exclaimed. "I see spots of blood."

They followed up the trail for some minutes, until even Pedro had to own that he had lost it.

"It's a pity," he said, stopping. "The tapir's flesh is very good, and it would have kept the men quiet for at least a day."

"Don't give it up," Derrick pleaded. "Listen! Isn't that—"

"You're right," cried Pedro. "That's the beast in the undergrowth."

Following the direction of the sounds they presently caught sight of the animal's hindquarters; but before either could fire it had disappeared.

"We have lost it," said Pedro. "A hunted tapir always makes for water, and swims under the surface."

"But if I hit it—There it is again," cried Derrick, as a crash sounded just ahead.

Once more they went on. It seemed that the tapir was making short plunging dashes through the jungle, stopping when it had outdistanced its pursuers, then bolting on as soon as it heard them getting near. Pedro led the chase, Derrick keeping close on his heels. The foliage overhead was not so dense as to exclude the daylight, and now and then Derrick caught sight of a squirrel or a monkey in the branches, and was tempted to try a shot at them. But Pedro said they were not worth wasting shot on while there was still a chance of securing the tapir.

Guided always by the sound of the heavy animal's movements through the undergrowth they pushed on, regardless of time or their increasing distance from the camp. Suddenly they spied the black form loping across a space where the vegetation was thin. Derrick again raised his rifle and fired, but his hand after the long chase was unsteady; he feared he must have missed, for the animal swerved to the left and disappeared. Its movements could still be heard, but its rushes were apparently becoming shorter, and the two lads, now filled with the ardour of the hunt, kept up the pursuit relentlessly.

At last they were brought up by a tangle of impenetrable thorn. They walked this way and that, trying in vain to find a gap.

"We can't get through this without a machete," said Pedro. "Perhaps Juan has his in his belt. Juan!" he called.

There was no answer.

"Didn't he follow us?" said Pedro.

"He certainly did at first," replied Derrick. "I was so keen on following you that I didn't miss him."

"He could have kept up without difficulty. Juan!" he called again. "The wretch is lazy, I suppose; or he was afraid he'd have to carry the tapir. We shall overtake him on the way back. And it's time we returned. It's getting late, and we shall soon have darkness upon us."

They waited for a few moments, listening. Juan had not answered Pedro's shout: they no longer heard any sound of the tapir's progress. Bathed in sweat, they mopped their dripping brows and turned to retrace their steps. And then Pedro stood stock still.

"What's the matter?" asked Derrick.

"I'm not sure of our direction," replied his cousin.

"But we can find our trail," said Derrick.

"Perhaps. But we've been moving round about since we were stopped by the thorns, and there's very little light. You had better stay where you are until I have had a look round. Undergrowth as thick as this shows very little trace of passage through it."

He went off alone. Derrick felt uneasy. He remembered having lost his way once on a moor in Sussex, and how impossible it had been to discover in the yielding bracken the track he had made only a few minutes before. Here in the subdued light of a tropical forest the difficulty was tenfold. Every now and then Pedro called, and he answered. Presently his cousin returned.

"Well?" said Derrick, looking at him anxiously.

"I can't find any track," said Pedro. "I was afraid to go very far, in case I got out of touch with you. Sound doesn't travel well in the forest."

"Don't you think we came that way?" asked Derrick, pointing.

"I should have said more to the right."

"Shall we try that way, then?"

"And what if it is the wrong direction?"

They were silent, and in their eyes as they looked at each other there spoke a terrible dread. It was the shock of realisation that they were lost in the forest.

CHAPTER THE SECOND - A NIGHT IN THE JUNGLE

Pedro looked at his watch. "What time did we start?" he asked.

"I haven't an idea," replied Derrick

"It's half-past five now," Pedro went on. "In half an hour the sun will be down: then it will be dark almost at once, as you know. We must have spent nearly an hour chasing the tapir."

"So we couldn't get back before dark even If we knew the way?"

"Unless the tapir led us in a circle. What has become of our wretched guide?"

He made a trumpet of his hands and sent a loud prolonged call rolling through the forest. There was no answer only a muffled echo: it seemed that the sound was blanketed by the vegetation all around. He fired his rifle twice in quick succession: the cracks met with no response except the flitting of a colony of bats disturbed in their leafy perch.

"What's to be done?" said Derrick, his voice sounding huskily.

"Keep cool," returned Pedro, smiling as he brushed the sweat out of his eyes. "I've heard of lost lonely travellers getting frantic: that's fatal. We have each other's company. Let us look at things calmly. It's hopeless to think of finding our way in the dark; we had better seek a shelter for the night. No doubt Juan and the crew will try to find us in the morning."

"They won't carry out their threat and paddle away down stream?"

"They won't dare!" cried Pedro, his black eyes flashing. "In any case we can find our own way tomorrow. Somewhere or other we shall come across a stream, and if we follow that we shall strike the river. The rest will be easy. So we had better set about finding a shelter while daylight lasts."

"Up a tree?"

"No, except as a last resource. I shouldn't feel comfortable in a tree: the forest animals are tree-climbers, many of them, and there are snakes. But the ground hereabouts is rocky: if we are lucky we shall find a bare spot somewhere, with perhaps a tall rock we can set our backs against. Let us try that rising ground over there."

They pushed their way through the undergrowth in the direction Pedro had indicated. The ground rose gradually, and the vegetation grew thinner as they proceeded. Presently they reached a fairly level stretch where there were no large trees, but only dense low-growing scrub.

"The soil's very thin," said Pedro, prodding with his rifle stock. "And see: here's bare rock, volcanic by the look of it. I think we are in luck's way."

They made towards a spot where the ground again rose steeply. Going round a patch of scrub, they found themselves opposite a rugged irregular wall of hard blackish rock, seven or eight feet high. In front of it was a floor of rock bare of vegetation, and here it seemed they might rest with some security from molestation by forest animals.

"It will be a hard bed," said Pedro, "and I am afraid a damp one, for the dew will be as thick as rain before long. But we can't do better."

"Are you sure?" said Derrick, who had wandered a few yards beyond his companion. "Look at this opening."

He pointed to a natural archway in the wall of rock, which appeared to be the entrance to a cave. They went in, looking heedfully around. A few yards within the entrance there was a small pool of water.

"I am frightfully thirsty," said Derrick. "Will it be safe to drink?"

"I am pretty sure of it," said Pedro. "I've myself drunk water from pools and streams and never taken any harm."

Derrick stooped and lapped up a mouthful.

"It's cold, and rather alkaline," he said. "I won't drink any more till I know it's safe."

Beyond the pool the cave was already almost completely dark. As a measure of precaution Pedro fired his revolver, standing aside at the entrance to avoid the rush of any wild animal that the sound might have disturbed. But there was no movement within, and the cousins agreed that Fortune had smiled on them in affording so convenient a shelter. They chose for their resting-place a flat slab of rock about a dozen paces from the entrance, gathered armfuls of grasses to soften their seat, and settled themselves with their backs against the cave wall just as darkness fell.

"We had better sleep in turn," Derrick suggested. "And keep our rifles between our knees," said Pedro. "Some beast may take it into its head to come in during the night."

"Couldn't we start a fire?"

"The plants are so damp that we should only raise a smother. I wish we had had something to eat. By the morning I, at any rate, shall be ravenous, and I daresay you'll have found your appetite too. Have you ever slept upright?"

"Sometimes, at lecture, after I've been up late."

"Well, I'll take first watch. Sleep if you can."

It was some time before Derrick's head nodded forward. At first he was kept awake by the various noises of the forest. From a distance came the hollow booming of frogs, proving that a stream must be somewhere in the neighbourhood. Monkeys yelped in the trees; the nightjar kept up its mournful cry; birds which Derrick could not identify chattered discordantly; and once he was startled by a shrill scream: some small creature had fallen a victim to a more powerful enemy.

He did not know how long he had slept when Pedro awakened him.

"Your turn, old boy," said his cousin. "I've had great difficulty in keeping awake. Nothing has happened. Good luck!"

In a moment Pedro had fallen asleep on his bent arms. Derrick straightened his back and gazed into the darkness. The sounds had died away except for the chorus of frogs and the low drone of myriad insects. Derrick sat musing, going over in his mind the incidents of his long journey, wondering how he would like the life on his aunt's estate, trying to divert his thoughts from the fact that he was lost in the Amazon forest. Presently he noticed that the darkness was thinning; he could make out the outline of the archway. "Surely it's not morning already," he thought, and then realised that the moon was rising. Its light increased: the beams struck directly into the entrance: and Derrick was suddenly aware of a strange flicker in the moonlight, like motes in a sunbeam: it was as if innumerable gnats were flitting in a giddy dance. All at once the flicker ceased; the moonbeam was clear radiance; Derrick supposed that the swarm of gnats had flown away into the open. But no: after a short interval the minute forms came again into the light; they danced for a few moments and again suddenly disappeared.

Derrick began to be interested. The coming and going of these tiny objects seemed to occur at regular intervals, and were always sudden. Idly, as a means of passing the time, he took to measuring the interval, counting as though marking the seconds. He found that the flickering lasted about half a minute: for half a minute it ceased: then it suddenly recurred, and after the same interval disappeared.

"Strange insects!" he thought. "They keep time like a clock."

He watched the periodic movement until the moonbeam slanted across the cave and finally left the entrance altogether. Then his thoughts wandered into other fields, and by the time he woke Pedro for another spell the phenomenon had passed from his mind.

The long night dragged itself out. When Pedro roused Derrick from his last nap the dawn was stealing into the cave.

"Sorry to disturb you, old man. You were snoring beautifully. You wouldn't snore if you kept your neck straight: I've learnt that."

"I'm frightfully stiff," said Derrick, getting up and stretching himself. "And hungry!-my word, I am hungry. But I suppose we can't get anything to eat in the forest, so the sooner we find our camp the better."

They left the cave and came into the open. The forest was alive with noise, trumpeter birds, macaws, parrots, monkeys vying with one another in creating pandemonium.

"I'll try another shot," said Pedro, "in case our men are searching for us."

But, as on the previous evening, the sound of the rifle-shot died away without awakening any response.

"Our direction should be eastward," said Derrick, "but we can't tell east from west until the sun gets higher. Shall we wait, or try our luck?"

"I'm for starting. Anything rather than inaction."

"Very well. But wait just a minute."

Derrick had suddenly remembered the strange phenomenon he had witnessed in the moonlight, and was curious to discover whether the multitude of gnats had their home in the cave. He walked back through the archway; several yards of the cave were now visible in the daylight. The floor was for the most part of hard volcanic rock, but at one spot, on the side opposite to his resting-place, he came upon a pocket of sand some nine or ten feet across; it was greyish in colour, and almost as finely divided as ground pepper. Derrick took up a handful, and let it slip through his fingers, half expecting a swarm of gnats to rise from it. But there was no sign of insect life: the fine particles, apparently, were nothing but sand.

He went all round the cave, poking here and there with his rifle. So far as he could discover, there was no nest of gnats. Retracing his steps, he was suddenly aware of a disturbance in the sand. "They are there after all," he thought, and stooped down to examine it more closely. Instantly he drew back, uttering a low cry: for his face was peppered by innumerable particles of sand, which stung his flesh and made his eyes smart.

"Pedro, come here," he called.

"What is it?" asked his cousin, entering hurriedly. "Nothing alarming, but something very strange," replied Derrick. He explained what he had seen in the moonlight, and the sudden upward shower of sand. "I was fairly pelted," he added: "it came with extraordinary force."

"Strange, indeed! Let us see if it happens again." They stood back against the wall. For half a minute there was no movement in the sand: then a small cloud of particles rose with astonishing velocity to the roof, where they appeared to cling. The cousins noticed now for the first time that the roof was deeply encrusted with this finely divided powder. They prodded it with their rifles, and a small quantity fell; but a good deal, though apparently quite loose, remained clinging to the roof.

The upward shower ceased, but in half a minute it was repeated.

"I never saw anything so extraordinary," said Derrick. "One would think that the roof had some magnetic attraction for the sand; but that can't be the explanation, because the attraction couldn't be switched on and off at regular intervals."

"We haven't time for scientific investigation," said Pedro. "We've still to find our camp. Someday, if you like, we can come back here and—"

"I say," Derrick interrupted, "I've just noticed another thing. That last shower happened just after a trickle of water from the pool had reached the sand. Let us watch: a few minutes won't make much difference to us." In a minute or two they had definitely established the coincidence. An upward flight of sand took place only when water had trickled on to it from the pool. This fact led to a further discovery: that the pool overflowed periodically, and the overflow was caused by a periodic inflow of water from a narrow fissure at the base of the arch. About twice a minute a small gush from the fissure entered the pool, and a tiny rivulet trickled over the rocky floor until it reached the sand. As soon as the water touched the fringe of the sand pocket, the particles covered by the water instantly sprang vertically upward as though under some electric impulsion. When the inflow from the fissure ceased, the overflow from the pool ceased correspondingly, and the sand was left dry and undisturbed.

"Well, have you solved the mystery?" asked Pedro quizzingly.

"No; it's deeper than before. All we know is that this water-it has an alkaline taste, you remember-appears to force the sand in mad haste towards the roof. But nothing is explained. We don't know the properties of the water, or of the sand: I haven't the least idea why the sand behaves as it does; but there's no question that when the sand and the water meet, a tremendous force is generated, and I shan't be happy until I know more about it."

"Now you really must come away. Have you forgotten that we are lost?"

"Upon my word I had almost forgotten it; but—"

He paused. The archway had been suddenly darkened. Looking round, the cousins saw a tall figure standing in the daylight.

"You've given me a mighty deal of trouble," growled the stranger.

CHAPTER THE THIRD - PAT HENEKY

DERRICK and his cousin often smiled in after days at this abrupt, unpromising opening of their friendship with Pat Heneky. At the moment the sight of a human being was so welcome that they were not disposed to resent a tone and manner which in other circumstances they might have found offensive. They hastened through the archway, Derrick exclaiming impulsively:

"Did Juan send you?"

"He did not, whoever Juan may be," said the stranger. He paused, looking from one to the other searchingly. "One English, t'other a dago," he murmured as if to himself. "Lost, I reckon?"

"Yes. We were chasing a tapir yesterday evening," said Derrick, "and couldn't find our way back."

"Catch the tapir?"

"No, unluckily."

There was another pause. The cousins looked with curiosity at this stranger, whose voice was soft and musical, but whose manner was brusque and off-hand. He was tall, very lean, his face deeply bronzed, his eyes light grey, his hair and beard mouse-coloured and slightly grizzled. He wore a dirty flannel shirt open at the neck, frayed corduroy breeches, buckskin leggings much the worse for wear, and boots that had seen neither dubbin nor blacking for many a day. A rifle was slung across his back; a revolver and a knife stuck conspicuously out of his belt; a bandolier crossed one shoulder; from the strap across the other hung a wallet and a water-bottle.

"Hungry, I reckon?" he said.

"Rather," Derrick acknowledged.

"And thirsty?"

"No; we've had a drink."

The stranger jerked his wallet to the front, undid the button, and took out a couple of ship's biscuits, somewhat soft to the touch.

"Can't spare any more," he said. "Breakfast presently. Ye'd better sit down."

Obediently as children the lads sat down on the rocky ground, crossed their legs, and began to eat the biscuits. The man leant against the side of the archway watching them.

"Heard your shots last evening," he said presently. "I reckon they was yours?"

"Yes," said Pedro. "I fired to attract Juan."

"Ah! Your Juan: maybe a shortish fellow, red shirt half-breed, eh?"

"That's the man," said Pedro."

"Saw him running through the jungle a while before I heard your shots. 'Sure 'tis a mighty hurry he's in,' thinks I. Then came the shots: Indians about?"

He took out a pipe, filled and lit it.

"I lay low," he went on. "Don't look for trouble. If 'twas not Indians, might be hunters. But when I heard no more shots, reckoned someone was lost and firing distress signals. Scouted around and struck your trail, a terrible zigzag, I'm telling you. It fell dark: 'twas too late to come up with you; I fixed myself up in a tree; and indeed I cursed you."

"We're sorry," murmured Derrick.

"And well ye might be, for 'twas the uneasiest night as ever I spent, and I've spent a many, and my canoe waiting for me not so far away.

"I wonder you bothered," said Derrick.

"That's because you're a tenderfoot. I've been lost myself; 'tis the way of going mad; I'd not wish it for my worst enemy. And white man must help white man: I knew ye were white by your trail. And now I've found ye, and you've had a cave to sleep in while I was perched uneasy in a tree!"

Derrick could not help smiling at the man's resentful tone.

"Who are ye, then?" asked the stranger suddenly. "And what do ye be doing here, youngsters and all?"

"We are on our way to Amarante," said Pedro.

"Where?"

"Amarante, in Bolivia."

"Cordillera del Amarante?"

"Yes: do you know it?"

"I have been there."

"Then you know the Alvarez mine?"

"There were not any mines when I was there."

"Then that was a long time ago. We've been there five years."

"'Tis a matter of seven years since I was there. You speak English, but you don't look it. Who are ye, then?"

"I'm Pedro Alvarez; my mother's an English-woman; I went to school in England; this is my cousin, Derrick Moore."

"Maybe Irish, like myself?"

"Not that I know of," said Derrick.

"And that's a pity. Well, now we are introjuced and ye can go on with your story."

"You haven't told us your name, though," said Derrick.

"I did think ye might know it, there being only one of me," said the Irishman, with apparent seriousness. "There's few between the Andes and the sea but know Roving Pat, though there might be thousands that don't know Pat Heneky, my name by christening. But how do ye come into this country, then?"

Pedro related the occasion of their journey.

"But why did ye not bring your machinery through the Canal to the Pacific, and then over the mountain road? 'Twould have saved ye a month at least, maybe more."

"The road is blocked by a landslide; there was an earthquake about six months ago; and it will take a year or more to clear it. We didn't come up the river by choice, I assure you. It has been a very tiresome journey, very hard work. Food has run short, our Indians are in a very sullen temper. If we had known what we were in for, probably we shouldn't have attempted the journey at all. But we are booked for it now. We left our camp on the river bank to pursue the tapir; if you can help us to find our way back we shall be very grateful."

"Well, maybe I can do that, if you'll give me a notion where your camp lies."

"Just below the rapids, where the river runs through a gorge of red rock. We lost one of our canoes there, and best part of our supplies."

"I know the place. Well, we'll make tracks; but ye'll have to go a bit out of your way, and pick up my canoe. And you can put away a trifle more breakfast I'm thinking. Keep close to me."

He led the way into the forest, following their track for some distance, then breaking off on his own narrower trail, which the lads themselves would not have discovered. Presently he stopped among some trees that were rather taller than the rest.

"There's your breakfast," he said.

They looked up, and saw some russet-coloured fruits shaped like pears.

"'Tis the wild alligator pear," said Heneky, "and the flavour will make ye sing praises."

While the lads gathered the fruit, Heneky stuck his knife into the bark of another tree. From the cut oozed a thick milky juice which he allowed to trickle into his mouth and swallowed with every sign of satisfaction.

"The milk-tree," he said. "I reckon you'll like it if you like toffee. Not but what 'tis powerful sticky, but we'll come to a stream by and by, and then you can wash out your mouths."

The lads found the alligator pears delicious, and in a short time a heap of the large stone kernels lay around them. They were satisfied with a mere taste of the juice of the milk-tree; then, refreshed, they set off again after their guide. Though there was no apparent track he walked rapidly, finding his way through the undergrowth with the ease of a practised forester. Every now and then he turned to make sure that the lads were keeping up with him, and his grey eyes twinkled as he noticed how the exertion in the steaming heat was telling upon them.

"Sure 'tis hard upon ye," he said once, "but you'll feel the good of the exercise before long. It cleans ye, inside and out."

They arrived by and by at a narrow stream, flowing sluggishly through a tangle of vegetation. Along one bank was a faintly marked trail. Following this for about half an hour they came to a small open space, evidently cleared by the woodman's axe. In the midst stood a hike tent; a birch-bark canoe was drawn up on the bank, and by it squatted a young half-naked Indian, who sprang up when he heard their footsteps, and looked searchingly at Heneky's companions. To him Heneky addressed a few words in his own tongue. The man grunted, at once struck the tent and laid it in the canoe, then dragged that light craft down to the water.

"Get you up into the bows," said Heneky to the boys. "I'll sit astern, and as we are going down stream Bola can do the paddling for us all."

Under the Indian's strong even strokes the canoe rapidly dropped down the stream, which soon merged into a broad river.

"This is your river," said Heneky. "In an hour or so we will come to your camp, and then you'll have no more need of me."

He seemed disinclined for conversation, and sat with his elbows on his knees, looking meditatively into the floor of the canoe. Derrick felt some curiosity as to what had brought the Irishman into these tropical wilds, and what occupation he followed; but the impassivity of the hard-bitten face forbade questions.

In about an hour they came within sight of the gorge, and rounding a bend, opened up the bluff where they had camped the day before.

"I don't see any sign of our party," said Derrick. "Nor of our canoes," added Pedro. "It looks as though Juan has allowed the men to go back after all."

"Unless they have made a portage and gone on."

"This Juan of yours," said Heneky, with a sudden return to actualities: "you know him well?"

"We don't really know him at all," said Pedro. "He met us at San Antonio-was engaged by a friend of my mother's."

Heneky ordered his Indian to run the canoe into the bank below the bluff, and there the whole party disembarked. There were traces of the previous day's encampment, and the number of empty tins lying about suggested that the Indians had made free with the remaining provisions. For the first time a misgiving seized upon the lads: had Juan returned safely to camp, or had he been lost, like themselves, and found no helper? Surely, if he had come back he would not have allowed the Indians to get out of hand. It seemed only too likely that the discontented crews had taken advantage of the absence of all their superiors to desert.

"Very awkward for us if they have," remarked Pedro. "Not so awkward as it would have been if we hadn't met Heneky," said Derrick. "At the worst I daresay he will take us on in his canoe. We could pay him, of course."

At this moment Heneky returned from a solitary reconnaissance some little distance upstream.

"There's no sign of a portage," he said. "It looks as if your men have carried out their threat."

"And taken Juan with them?" said Derrick.

"Maybe; maybe thrown him into the river. Why, what's this?"

He was standing facing the river; the others had their backs to it. Turning at his words, they saw him pointing to a spot below the bluff where the stream ran shallow. Just below the surface they caught sight of the gleam of metal. They hastened down the bank. At Heneky's order the Indian waded into the water and fished up the gleaming object. It was a cylindrical bar of steel.

"Part of our cargo," said Derrick in amazement.

"And there's more," said Heneky. "I'm afraid the men jettisoned that machinery of yours."

"Worse and worse," said Derrick.

He stripped off his boots, entered the water and plunging his arm in, brought out a canvas-covered package.

"There's no doubt about it," he said. "They've dumped our stuff here to lighten the canoes and bolted."

"And taken everything else, I reckon," said Heneky. "The machinery would be no use to them, but your personal belongings would make 'em rich."

"And they've gone downstream: is there any chance of catching them?" Derrick asked.

"'Tis some twenty hours since you left them," said Heneky, "but they wouldn't bolt at once, expecting you to return. And they wouldn't travel by night. They've had maybe four or five hours' start: the canoes are dug-outs?"

"Yes."

"Then I think we can do it, Bola and me. We'll try, anyway."

Two minutes later Heneky and his Indian, each plying a paddle, were driving the birch-bark canoe at a spanking pace downstream. In about an hour they came to the fork where on the previous day there had been a difference of opinion as to which branch of the river should be taken. Heneky showed no hesitation, but swung the canoe round into the branch that struck away to the south.

"Why not go straight down?" Derrick asked.

"Because they came straight up," replied Heneky.

"That's reason enough for their choosing this arm. And as they are now going upstream, and won't suppose you've any means of chasing them, I shouldn't be surprised if we overhaul them pretty quickly."

Even against the current the light canoe made rapid progress. The paddles moved with the regularity of clockwork, and Derrick admired the ease and dexterity with which Heneky and his Indian, working in perfect accord, steered their craft at the bends so as to keep the shortest course. But it was not until more than two hours later that, shaving the bank at one of these bends, Bola suddenly exclaimed that he saw canoes ahead. Heneky instantly steered towards the left bank, to get cover from the trees that overhung the river, and only when he was less than a hundred yards behind the dug-outs did he come openly into midstream.

All unsuspicious of pursuit, the runaway Indians were paddling slowly.

"Let off your gun," said Heneky to Pedro.

At the sound of the shot the Indians turned their heads, and hung upon their paddles. The canoes swung broadside to the current. Next moment a shout broke from the men, and in the foremost canoe Juan, standing upright, waved his arms with every sign of delighted welcome.

CHAPTER THE FOURTH - JUAN COMES TO HEEL

BOLA drove the Irishman's canoe on until he brought it alongside that in which Juan stood.

"You'll leave this to me, boys," Heneky had said as they approached: "if you please of course. I'm more than double your age, I guess, and have maybe ten times your experience, and I've a notion of putting a question or two to that half-breed"

"We'll be only too glad," said Derrick. "I never liked the fellow."

Heneky gave a few sharp words of command to the occupants of the other two canoes in their own dialect. Without hesitation they paddled to the left bank of the river, and kept their craft stationary by holding on to overhanging branches.

"Now you," Heneky went on in English, addressing Juan: "slide yourself into this canoe, and be quick about it."

The man looked darkly at the speaker as if meditating a refusal; it was probably a dangerous glint in the Irishman's eyes, and the set of his square jaw, that prompted obedience. He threw a leg over the side of his own canoe into the other, and slid to the bottom; whereupon Heneky ordered the Indians in the craft he had left to join their companions, while Bola paddled just sufficiently to prevent the lighter vessel from drifting down on the tide.

"Now then, you'll tell me a thing or two," Heneky went on. "You left these gentlemen when they were hunting tapir yesterday, and I'll have ye tell me why."

"I will tell, sure," said the man glibly. "I was behind; they go too fast; I lose sight of them. All at once, presto, I am attacked by wild Indians. What can I? I run quick, as quick as I can; they run after me; how can I escape? I cry for help: there is none to hear; I run; they howl like wolves. I stop; I turn and fire at them through the trees; ah! that is good; they wait; I run again, but they come still after me. Yet I run more quick, for it is my life I save, and I come at last to the camp, and then-yes, they are cowards; they come no more; they go back: I am safe."

"And then?" asked Heneky curtly.

"Ah! Then I wait for the señores. It grows dark; I have great fears; are the señores alive? I know not; I wait; if they are alive, they come back, sure. But they come not back; all the night I shake with fear; in the morning, I think, they will come. But they come not: the Indians have killed them; all the men say so; what use to wait more? We must make ourselves safe; and so!"

"And the machinery you dumped in the river?" "The men; the lazy men! They say the load too heavy for us to go quick, and so!"

The man had spoken with apparent candour, his arms working like a marionette's. Heneky nodded, pressed his lips tightly together, then ordered Bola to paddle to the trees under which the other canoes lay. Throwing a quick glance over the dark faces of their crews, Heneky picked out, as he afterwards explained, the most intelligent-looking of the men, and held a short conversation with him in his own language. While the Indian was speaking, Derrick noticed that Juan grew more and more uneasy. He scowled, bit his lips, looked around as though searching for a refuge. Heneky's face was expressionless. Presently he turned to Juan.

"Give me your rifle," he said, and as Juan hesitated, the Irishman, with a sudden movement, drew the strap over his head. He examined the barrel. Again he spoke to the Indian, asking two or three brief questions, each of which the man answered in a word.

"Get back into your dug-out," said Heneky curtly.

Juan held out his hand for his rifle.

"No, I'll keep that," said the Irishman. "And don't try to get away, or maybe you'll get a bullet in your back."

He ordered Bola to let the canoe drift a few yards downstream, then once more to bring it to rest under a tree, out of earshot.

"That's a grand liar of yours," he said to the boys. "You heard him say he fired at the Indians that were chasing him? Well, his rifle's as clean as clean. I asked that Indian fellow which of the crew cleaned it. 'None of them,' says he. I asked if Juan had cleaned it himself. He had not, says the man. The rifle had not been fired at all. And what's more, the story he told us is not what he told your crews. He told them that he'd seen ye killed in the forest. And he didn't wait for darkness, but dropped downstream at once to the fork, and spent the night under the bank of this very river. A grand liar! 'Twas he that ordered the men to throw your machinery overboard."

"But what on earth is the fellow's motive?" asked Derrick. "What has he to gain?"

"Indeed that's what's puzzling me," said Heneky. "Have ye an enemy in your parts?" he asked Pedro. "Among the mine-owners, I mean."

"No. There's no other mine anywhere near us; no neighbours at all for a good many miles."

"It came into my head that if ye'd an enemy he might have bought this fellow to lose your machinery for you. But 'tis worse than that. The man misled you, for 'tis this arm of the river you ought to have taken yesterday, not t'other: he knew that well enough. And 'tis clear he'd have been delighted to lose the two of you, and indeed thought he had lost you. I'd be after calling him a murderer as well as a liar."

"I never liked him, but I can hardly believe that," said Derrick.

"I could believe anything of him," said Pedro, warm with indignation. "You don't know the half-breeds as I do. Not that they are all blackguards, of course, but when they are bad they are-horrid isn't strong enough. Yet, like you, I can't see any motive for the wretch's villainy. It's clear we can't trust him an inch farther; what are we to do with him?"

"I say turn him adrift in the forest," said Heneky bluntly, "I'd serve him as he wished to serve you. 'Tis the law of the jungle."

"We can't do that," said Derrick.

"I don't see why not," said Pedro. "It's not English, but out here—"

"You don't really mean it, old chap," said Derrick. "It's not cricket: you went to school in England, and know that. Why shouldn't we hand him over to the Bolivian authorities nearest your place?"

"Indeed and you're a tenderfoot," said Heneky, with a slight smile. "Bolivian authorities, begore! I've had some dealings with the Bolivian officials, and sorra a bit of justice ye'll get out of them, except maybe you buy it. Besides, what'll ye charge the fellow with? He's a liar; well, all men are that, as one said of old. He could tell a plausible story, one that would go down well with your Bolivian officials. No, indeed; turn him out to grass, that's my advice to ye."

"Quite impossible," said Derrick. "And I want to fathom the man's motive. If your suspicions are well founded, there's something behind all this, and it's mere self-interest to keep a hold of the man until we know more."

"And there's truth in that," Heneky admitted. "Well then, you and me are not to part company yet awhile, for I wouldn't feel easy to leave such lambs unprotected. I must see you safe to the end of your journey."

"But we should be giving you trouble-taking you out of your way."

"Trouble! 'Tis what a man's born to. My way! My way's every way. Roving Pat they call me-them as knows. But if ye don't want me, sure ye've only to say the word: Pat Heneky will not force his company on any mortal soul."

"Of course we shall be delighted, shan't we, Pedro?" said Derrick. "We couldn't wish for anything better, only we owe you so much already."

"Indeed 'tis a trifle," said Heneky. "And believe you me, there's a fate in it. 'Tis appointed I am to be your guide."

"Thank you ever so much. And you'll take command? The Indians will obey you."

"I'll not be surprised if they will," said the Irishman, complacently. "So we'll set off now, and first retrieve your machinery-a job for Juan. Them as lose can find."

Returning to the stationary canoes, Heneky told the men curtly that they were to paddle back to their encampment of the previous day. As if by an afterthought, he ordered Juan to take one of the paddles.

"But it is not the work for me," the man protested hotly. "I am-I am a gentleman. I do no work of Indians."

"Indeed now, 'tis not so dirty as all that. And I'll be telling you, Mister Juan, you'll do as I bid you, and without grumbling, or I'll put you ashore by your lone self. Make up your mind to it."

The half-breed's eyes darted venom, but he picked up the paddle in sullen silence, and when the word was given to go, plunged it with a vicious dig into the water.

Heneky sent the dug-outs in line ahead, Juan being in the one immediately in front of the birch-bark canoe, which Bola paddled alone. It was a quick run downstream to the fork, but when they turned into the northern branch, and had to contend with the full force of the current, the heavier craft made slow progress. Juan, who had quite truthfully said that he was unused to work commonly done by the natives, was soon sweating freely, and began to flag.

"'Tis my notion of a gentleman that he won't be beat by them as haven't got blood to boast of," remarked Heneky drily. "Put your back into it, Mister; you're blocking the traffic. You ought to set an example to my poor Indian; he has not had your advantages, indeed he has not. But he's too polite to pass you; and what's more, I wouldn't dream of leaving you behind; so dig your paddle deep, Mister; the sooner we're upstream, the sooner we'll be down again."

Goaded by the Irishman's sarcastic admonitions, Juan plied his paddle with as much vigour as he was capable of, and earned by and by a word of patronising approval.

Arriving at the place where the packages of machinery had been thrown overboard, the men were set to haul them out of the bed of the stream. Juan sat down on the bank, and began to wipe his hot face with the sleeve of his shirt.

"No, no, that won't do at all," said Heneky, who had stepped on to the bank with the boys. "'Twas a little mistake, to be sure; an error of judgment which I'm sure you are sorry for, like a gentleman; and so you'll lend these poor ignorant fellows a hand."

"I will not," retorted the half-breed savagely. "I melt; my arms have pain; see, on my hands are blisters. I do no more."

He folded his arms and dug his feet resolutely into the soft earth. Heneky quickly moved to a tree nearby, and taking his knife from his belt, cut a stout switch from a low-lying branch. Then, swishing it through the air, he returned and stood over the seated man.

"Now, you treacherous hound!" he said in Spanish, not raising his voice. "You owe your life to these young men whose destruction you plotted. I would have put you ashore to meet the fate you intended for them. They had mercy on you. But now you must work. You dumped that stuff in the river, and by all the saints you shall help to haul it out. Ah! you would!"

Juan had made a quick snatch at his belt, from which the haft of a long knife protruded. Heneky, by nature a man of slow and deliberate movement, now showed himself capable of extraordinarily rapid action. The switch in his hand hissed through the air and fell unerringly on Juan's fingers as they closed on the haft. The man let out a yell of pain and rage; the knife dropped to the ground. At the same moment Heneky grasped him by the collar and hauled him to his feet; then, holding him at arm's length, in spite of furious struggles punctuated by screams and oaths, he silently dealt him half a dozen cuts on the back with all the strength of an exceedingly muscular arm. Without loosing his grip on his writhing victim, he quietly asked:

"More?"

For a moment the man made no reply. Fear and hate contended in his distorted face. Then, swallowing in his throat, he breathed out a sullen "No!"

"Then set about your job," said Heneky, releasing him. At the same time he kicked the knife far into the river.

Juan stood for a moment with fists clenched, his features quivering. Then, without waiting to pull off his boots, he splashed into the water, and with frenzied energy began to lug the heavy packages from their muddy resting-place.

CHAPTER THE FIFTH - THE MINE

THE boys had looked on, with silent admiration, at Heneky's cool masterfulness. Alone of the two, Pedro had understood the Irishman's words. Translating these to Derrick, he added:

"He has plenty of courage. He has made a mortal enemy of Juan, and the man-I know his breed-will never rest until he has taken his revenge. Heneky must look out."

"I daresay Juan regrets his error of judgment," said Derrick. "A double error: he dropped some of the stuff into pretty deep water."

Some of the men had to work waist-deep in the river in recovering the packages: now and then they were compelled to dive in order to pass ropes underneath them. Standing like a grim overseer on the bank, Heneky mingled encouraging words to the Indians with stern orders to Juan, seeing to it that the man did his fair share of the work. Retribution had followed swiftly on the offence. Juan was pallid, partly with suppressed rage, partly with the taxing of his flabby muscles. He winced when, getting his hand among the cogs of a wheel, he scraped the skin from his fingers and withdrew them bleeding.

A little while after there was a panic rush of the whole party for the bank. The Indians, squealing with fright, dropped their burdens, leapt through the water, and scrambled ashore in a heap. Juan was a little behind the rest, and when he had heaved himself up among them, he clapped his hand upon his ankle, and a trail of blood was seen upon his legging. A moment later Bola, who had remained in his canoe, snatched up a short spear that lay beside him, leant over, plunged the spear into the water, and withdrew it with a short thick-bodied fish impaled upon it.

"A piranha," remarked Heneky. "They are worse than sharks or alligators. Demons, I call them. Look you at its ugly jaws."

He took the fish from the spear, and showed Derrick its gaping jaw and wedge-shaped teeth as sharp as razors.

"They'll cut you to the bone," he said. "And indeed I fear we'll get no more work out of Juan to-day."

Though the man's wound proved to be only a slight laceration of the flesh, Heneky was not so hardhearted as to compel him to re-enter the water. It was in fact some time before any of the Indians could be induced to resume work, fearing mutilation by the ferocious fish, and then some of them kept up a constant agitation of the water with their paddles in order to scare the pests away. The consequent delay, and the difficulty of removing the heavy packages from their muddy bed, prolonged the task into the afternoon, and by the time it was completed Heneky declared for remaining on the bluff for the night.

While they took a sparing meal from the little stock of provisions which the natives had left, Heneky showed himself to be a more agreeable companion than his brusque and off-hand manner had promised. In his slow melodious voice he regaled the boys with stories of his wanderings in the forest, gathering rubber, prospecting, trading for nearly twenty years. As a youth he had come out as an engine-hand on a tramp steamer, and the boys gathered that he had deserted in quest of adventure, but on this part of his career he was somewhat mysterious.

"I've fried too many fish, and that's the truth of it," he said. "My meaning is that I'm never a bit better off than I was twenty years ago, because I've had a fancy for too many things. I'm Roving Pat, and will be till I go under. Now I'll give ye a guess what I'd do if I had my time over again."

"I'm no good at guessing," said Derrick.

"A soldier; that's what I'd like myself," said Pedro.

"That's very wide of it, so I'll tell ye. If I were your age, I'd take to flying. 'Twas not heard of when I was a boy, and in the early days I mocked, like a good many more: how'd they be the way of navigating the sky in a machine heavier than air? But the idea got a grip of me; it gave me the flutters when I first saw Bleriot soaring aloft as smooth as a bird, and 'tis a trouble to me that I've never had a chance of it. Have ye ever been up, now?"

"I had a flight once," replied Derrick: "just ten minutes round and about an aerodrome: it cost me half a guinea."

"And didn't ye get your money's worth?" asked Heneky eagerly. "Didn't ye feel your heart light and your soul free?"

"I don't know about that," said Derrick, smiling.

"It's a queer sensation to feel the earth running away from you."

"By the powers, 'tis a feeling I'd like to have before I die." And then the Irishman astonished the boys by the extent of his information on aeroplanes and the art of flying. Having discovered a common interest between them, he expanded, opened out, and talked on and on, discussing the relative merits of the biplane and the monoplane, talking familiarly of the Curtis, Breguet and de Havilland types, retailing the exploits of famous airmen, and displaying an amazingly up-to-date knowledge of the most recent developments. Presently he went down to his canoe and returned with an armful of journals and magazines, and by the light of the camp lantern held forth to his interested hearers on the illustrations and diagrams of various machines, reading aloud in his pleasant voice paragraphs of description that had specially captured h1s imagination.

"And I tell ye," he said, "that this Amazon valley, and for that matter the greater part of the South American continent, is just waiting for the aeroplane, as you may say. And sure we'll see wonderful things before we're much older. Of course the need is for a handier machine than they've got at present, one that doesn't depend on aerodromes, that'll rise anywhere and at any time, and carry any weight. 'Twill come some day or other, and 'tis my hope I'll live to see the day. Why now, think of it: what you lads would have been saved if ye'd been able to come by aeroplane. Ye'd have done the journey in a day or two. Why, you could be at home in half an hour from this very spot. Your mine, I guess, isn't above forty miles away as the crow flies, and the aeroplane'll go as straight and faster than a crow. But there's a six-thousand-foot mountain between, and that means a roundabout river journey of a good hundred miles, and several awkward portages. If you hadn't got your machinery I could lead you across the hills; 'twould be only a couple of days hard marching. As it is you must follow the river, and 'twill take you a week. However, time's of no account on the Amazon, or anywhere else on this continent, for the matter of that. 'Tis only in the towns that ye have to keep your eye on the clock, and for myself, I'd not live in a town for all the gold and diamonds in all the world."

They sat talking till far into the night: yet Heneky had the men stirring soon after daybreak, so that they might get well on their way before the heat of noon. The boys grew more and more pleased with their new companion. Under Juan's lax control the Indians had been lazy: with Heneky they worked harder and progress was more rapid. And Heneky took care that Juan himself did not shirk his new job as paddler. Ever since his swishing the man had been sulky and morose; he rarely spoke, and, to judge by the scowl upon his brow and the malignant gleam in his eyes, dark thoughts were seething in his mind. Heneky watched him narrowly, and when the party camped at night, he chose a position for the tents where surprise would not be easy, kept his revolver always handy, and arranged that one or other of the Europeans should always be on watch.

In spite of his care, however, it was discovered early one morning, when, according to Heneky they were within two days' journey of the Alvarez hacienda that Juan had vanished. The Indians professed not to know when he had left the camp, or where he had gone, and Heneky sent Bola to find his trail in the forest. Returning after a short search, the Indian reported that the track ran towards the north-west.

"That's not our way," said Heneky at once.

"We'll not waste time following him, and if the spalpeen comes to a bad end, sure he'll deserve it. And 'tis my hope that we've seen the last of him, though I misdoubt it."

Some twenty-four hours later they arrived at a spot where the river journey must end. Derrick had noticed changes in the vegetation along the banks. There was less jungle; the trees were smaller and there came into view the peaks of the Andes, which had before been hidden by the forest. The remainder of the journey was to be accomplished on foot, across a rocky tableland in the foothills of the mountain range. The machinery, which at the portages had been carried part at a time, was too heavy to be conveyed all at once, and it was left in a little hollow some distance from the river, from which it would presently be removed on wagons sent from the mine. As the party marched, Heneky pointed out the snow-clad peaks of Mont Sorata and Mont Illimani in the far distance, showing an acquaintance with the country that surprised even Pedro. Then they struck into a beautiful valley winding between sloping heights, with broad expanses of grassland merging into stony hills. At a sudden turn Derrick had his first sight of his aunt's hacienda, a low brightly-painted bungalow of stone and wood, in the midst of a large garden surrounded by a paling. On the hillside beyond he noticed a number of small wooden huts, which Pedro told him were the dwellings of the miners.

Long before they reached the place they were welcomed by the barking of dogs, and a lady appeared at the gate amid a group of excited servants. At the same time a number of short figures came into view among the huts, their gestures showing their interest in the arrival of the party. Pedro hastened ahead to greet his mother, and linking his arm in hers brought her along the road.

"This is Derrick, madre," he said. "You won't recognise him."

"He was hardly more than a baby when I last saw him," said the Señora Alvarez, with a charming smile. "How do you do? Welcome to my little home. I hope you had a pleasant journey, and that you will be very happy while you stay with us."

"I am sure I shall, Aunt Bertha," said Derrick.

"He says nothing of the journey, you see," said Pedro, laughing. "Indeed, I'm afraid he found it rather trying. But I must introduce a new friend to you, madre. Without Mr. Heneky—"

"Pat Heneky-Roving Pat for short," the Irishma corrected. He had stood hat in hand a little behind the boys.

"Well, Roving Pat, then," said Pedro drawing him forward. "Without him we should not have been here to-day, perhaps not at all."

Señora Alvarez looked surprised and alarmed.

"What happened?" she asked. "But let us go on to the veranda: you must tell me all about it. I need not say that Mr. Heneky—"

"Pat, ma'am. Sure I don't know myself at all if you mister me."

"You are very welcome," said the lady avoiding the name. "Let us all go in."

With Pedro she led the way up the garden to the pillared veranda, where cushioned cane chairs were ranged around a bamboo table. Neat smiling native servants brought cooling drinks from the house, and then the lady asked her son to explain what he had meant.

"I don't think much of that fellow Juan you sent us as guide, madre," said Pedro. "In fact, I'm afraid he's a thorough scamp."

"But, my dear, I know nothing about your guide," said his mother. "I sent word to Señor Pando at San Antonio that a guide would be required; you remember him: a respectable lawyer; and I took it for granted that he would provide a trustworthy man. I am seriously annoyed. But tell me: how did the guide fail you?"

Pedro related briefly the incidents of the journey, dwelling particularly on the fortunate meeting with Pat Heneky when he and Derrick had been lost in the forest and deliberately abandoned by Juan.

Señora Alvarez listened attentively, her face expressing growing concern as the story proceeded.

"It is all very strange," she said. "I too have some grave news to give you."

"The landslide? You sent me word about that," said Pedro.

"It is what followed the landslide," said his mother.

"That was due to an earthquake, and it not only blocked up the road from La Paz, but destroyed a great part of the mine workings. I kept that from you, because I didn't wish to worry you. I have had a very anxious time. I set the men to save everything it was possible to save, and I was astonished to find that Diego-he is the engineer, Derrick-seemed to put all sorts of obstacles in their way. He seemed to hinder rather than to help, and one day I was amazed to learn that he had taken it upon himself to dismiss the men to their homes, telling them that it was quite useless to do any more until the new machinery arrived. I protested, rather warmly, as you may imagine, and the result was that he took himself off, suddenly and without notice, and I haven't seen him since."

"The wretch!" said Pedro. "Can one ever trust these low-class Bolivians? I am glad I am half English, madre."

"A strange thing was that for a fortnight before he left he was constantly in the company of a stranger whom he did not introduce to me, but who, I was told, was his brother. This man came here a few weeks after the landslide, and he went all over the mine workings with Diego, showing what I thought was a natural curiosity about the devastation that had occurred. I did not like the look of the man, still less the look of a servant he brought with him-a little man with a most evil face who followed him like a shadow. I always knew where the master was, even if I could not see him, for the man's red shirt—"

"Bedad now!" exclaimed Heneky. Señora Alvarez looked at him in surprise.

"Sure and I ask your pardon, ma'am," said the Irishman, "but 'tis the truth's truth that the spalpeen Juan did be wearing a red shirt, and a thought came into my head."

"You think he was the same man?" asked Pedro.

"Indeed I thought he might," said Heneky.

The lad looked distressed.

"I do hope it is not so," said Señora Alvarez, "because if it is, it does appear that Diego, or his brother, or both of them, are malicious."

"It seems hardly likely," said Derrick: "I mean hardly likely that they got this servant-man employed as our guide, for I gather that your engineer has not long left you. Did his brother go with him?"

"Yes, they went away together about a fortnight ago."

"And it is three weeks ago that Juan came to us at San Antonio."

"But the man with the red shirt left before his master. I missed him one day. Of course I had never said anything about him to Diego; I did not wish to appear inquisitive about his friends. I never saw him again after that day."

"Is your mine working, ma'am?" asked Heneky, the sudden change of topic surprising his hearers.

"No, nothing has been done for five or six weeks. Why do you ask?"

"Because, ma'am, you'll pardon me for putting my spoke in, and me a stranger-because you must start work again without any delay."

"Why?" asked Pedro, struck by a certain grave emphasis in the man's tone.

"Because if you do not, you'll lose your mine. Maybe you do not know it, but that's the law in Bolivia."

CHAPTER THE SIXTH - SEEING IS BELIEVING

SINCE the death of her husband the Señora Alvarez had carried on the working of the mine in the face of considerable difficulties. An Englishwoman, she had had to rely on the natives whom the señor had employed, but with whom during his lifetime she had seldom come into contact. She would have liked to replace the chief engineer by a countryman of her own, but hesitated to dismiss him without any reason except a vague sense of distrust. His spontaneous departure had thrown the way open, and she had only awaited the return of her son in order to take steps for the engagement of a competent successor of British birth and training.

This matter was discussed among the party of four as they sat in the veranda, while the servants were preparing a meal. Pedro pointed out that a suitable man must not only be a mechanical engineer but have a practical knowledge of mining.

"If it weren't for that," he said, "Derrick and I might carry on for a while, because we've both had a little elementary training in mechanics. But we know nothing about mines. I suppose we had better advertise in English papers."

"It would take months to find and bring out a suitable man," said his mother. "By the way, we have had no news from La Paz for the past fortnight. There has been no post, and my usual batch of papers and magazines from home has not arrived. The blocking of the road appears to be more serious than I had supposed."

"But we can surely get a messenger through," said Pedro. "We ought to have the telegraph or telephone by this time."

"Or maybe an aeroplane," suggested Heneky.

"I'm afraid we are a long way from that," said Señora Alvarez, smiling.

"Well, what are we to do?" said Pedro, insistently. "If Pat is right, and the mine ceases to belong to us by the mere fact of our ceasing to work it—"

"How can that be?" Derrick interrupted. "You can't work a mine that has been destroyed by an earthquake."

"I don't suppose any provision was made for earthquakes in our mining laws," said Pedro. "As I was saying, if Pat is right, we can't wait to get a man from England, or even from the States. We shall have to appoint another Bolivian."

At this moment they were summoned within to a meal, and Señora Alvarez insisted that the subject should be dropped until later. While they were at table Heneky kept them amused with stories of his experiences in various parts of the continent, and the hostess by and by murmured in Pedro's ear:

"I like your new friend...You look very thoughtful, Derrick," she added. "I hope you are not wishing you had not come."

"Not at all, Aunt," said Derrick. "I was-I was just thinking."

"A penny for them."

"You shall have them for love, Aunt-by and by."

She gave him a look of comprehension, and turned to speak to Heneky.

"I am afraid these boys have brought you far out of your way, but you will stay the night, won't you?"

"Indeed, ma'am, I'd not wish to trouble you, and me not sleeping under a roof once in a blue moon."

"Then you will enjoy it all the more, and give us all pleasure."

"Well then, ma'am, I'll be proud, and I thank you kindly."

When they rose from the table, and Heneky with his pipe was established again on the veranda, Derrick found an opportunity of drawing his aunt and cousin apart.

"This is what I was thinking," he said. "Pat Heneky was a ship's engineer, and since he dropped that he's tried his hand at no end of things, including mining. Don't you think he might be asked to carry on here until you get a permanent man?"

"A capital idea!" said Pedro. "You said you like him, madre."

"I do," said his mother. "He has honest eyes; but—"

"But you think he's too much a Jack-of-all-trades, isn't that it? That's very likely true, but I wouldn't suggest keeping him permanently. The main thing is that he probably knows enough of mining to keep things going until we find a satisfactory successor to Diego, and it's an unquestionable fact that he has a masterful way with the natives, and that counts for a great deal."

"Very well: will you ask him?"

"You had better ask him yourself," returned Pedro with a smile. "He's an Irishman, you know."

"Flatterer!" said the lady, patting her son's arm. "Well, I'll see what I can do."

She went on to the veranda.

"Don't get up, Mr. Heneky," she said, as the man half rose from his chair.

"Roving Pat, ma'am," he said reproachfully.

"Well, I'll call you Pat, if you wish it, but I don't want you to rove again for a while. I want you to do me a favour."

"Anything in the wide world, ma'am," said the Irishman gallantly.

"Then will you stay here and look after things for me until I can engage a new overseer? My son tells me that you are an engineer and know something of mining also, and I shall be greatly obliged to you if you can see your way to help me in the present unfortunate state of things."

"I never could say no to a lady, ma'am. 'Tis true I had no thought of any such job, having a job of my own; but 'tis no hurry for that. It has waited a good few years already, and a few more weeks or months will not matter a great deal."

"It is very kind of you," said the señora, wondering what was the business that had brought so hard and steely a look into Heneky's grey eyes. "Let us be quite business-like: I propose to pay you a hundred and fifty dollars a month."

"Indeed, and that seems a mighty fair wage," said Heneky, "and the same as ye paid your Bolivian, ma'am'?"

He looked at the lady shrewdly, humorously. "Well, no, it is a little more," she admitted. "You're English, you see."

"Sorra a bit, ma'am. I'm Irish blood and bone. But I know what you do be meaning, and I cannot agree to it. I could not take more than your last man, me not being a trained engineer. But I will not take less, because I reckon I'll do as well as he. So you'll be pleased to give me the same, ma'am, and I'll do my best until you get a better man."

The boys were amused when Señora Alvarez reported the result of her interview.

"He's a queer fellow," said Derrick, "but I believe he's perfectly straight, and I'm more than ever glad we met him."

Meanwhile the new machinery had been brought up on mule waggons. Heneky suggested that it should be deposited for the present in the grounds of the hacienda. This having been done the Indians were paid off and returned to their canoes.

It was now too late in the day for Heneky to inspect the devastated mine, but he was out before the others were up next morning, and when he returned for breakfast he had formed a pretty clear idea of the state of affairs. The mine lay on a hillside only a few hundred yards from the hacienda. The workings had been almost entirely obliterated by the landslide. Here and there were fragments of machinery, a tank crumpled up, a compressed air drill in ruins; and there was a large number of broken steel trucks, which had been used on a narrow-gauge railway for conveying the ore from the mine to the crushing mill by the stream below. It was evident that months of labour would be needed to clear away the accumulation of shattered rocks and put the mine into a thorough state of repair. Actual mining must inevitably be suspended, but Heneky argued that the work of clearance and repair was sufficiently within the law to remove all fear of dispossession.

Immediately after breakfast he set about the practical exercise of his new duties. He mustered all the labourers, addressed them in their own language, told them that they would now have to earn their wages instead of lolling in idleness, and dividing them into gangs, allotted to each a definite part of the mine for the clearing of which they would be responsible. The men recognised a master, and from that time work went on steadily day by day.

But there were many holidays. Derrick was amazed at the number of saints' days, on which work was suspended, and the men spent their time in card-playing and various forms of gambling. Such feasts the cousins took advantage of to go on hunting and shooting expeditions in the neighbourhood, sometimes being accompanied by Heneky when they could persuade him to take a little relaxation from his work of supervision.

One day, in the course of such an expedition, while the three were eating their midday meal, a sudden gust of wind sweeping up the face of the hillside brought a cloud of dust swirling about them, tossing the particles high into the air.

"Rather like the animated dust in our cave, Pedro," said Derrick.

"Yes; I'd almost forgotten it," said his cousin.

"How keen you were to discover an explanation of it!"

"So I am still, but there's been no time to think of it lately."

"And what might you be meaning by animated dust?" asked Heneky.

Derrick related his discovery, and suggested a theory that the water had some chemical effect on the sand, resulting in lively motion.

"It's kidding me you are," said Heneky. "Did ye ever hear of spilling salt on a bird's tail?"

"Really, I'm not gammoning," said Derrick. "I could hardly believe it myself when I first discovered that what I had thought to be a swarm of gnats was an upward shower of sand, but Pedro can back me up, and we are both positive that the sand only flew to the roof when the water flowed in upon it."

"Well, I've seen strange things myself, but never anything so strange as that. I will not say I do not believe you, because that would be rude; but seeing is believing, as they say."

"Then why not see?" asked Derrick. "You could find that cave again?"

"Sure, and it's not so very far from here if we take the short way. 'Tis a stiff march through the hills, but we'll get there by sundown if you step out. Of course, it means a night or two in the forest."

"It's hardly worth while," said Pedro. "I'm not at all keen on a long march."

"And I don't agree with you at all," said the Irishman emphatically. "You tell me of a strange, wonderful freak of Nature, for that's what it is if you did not dream it all. Well, I was born curious, and all my life long I've been driven to find out the meaning of things. What you tell me is like a strop to a razor, and if you won't come, bedad and I'll go my lone self: not but what it'll be time wasted, for I reckon you're somehow mistook."

"That's a challenge," said Derrick. "Let's start at once. If it isn't as I say I'll eat my hat-and yours too, Pat."

Heneky smiled; his hat was ancient and dirty, by no means a dainty morsel. Pedro, though reluctant, raised no further opposition, and they set off together. Heneky had truthfully described the march as a stiff one. At first, while in the foothills, they had to tramp over hard rock and loose stones, to spring across fissures and wade turbulent little mountain streams. As the ground descended they came by and by into a region of swamp and quagmire, where many strange birds tempted Derrick to use his gun. Then they entered thin jungle and were pestered by myriad insects.

"I wish to goodness you had forgotten your dancing sand," said Pedro presently.

"Sure that's not my wish," said Heneky. "'Tis worth a little trouble to see a marvel-if 'tis not all a dream."

Evening was drawing on when they at last reached the neighbourhood of the cave. Heneky, familiar though he was with the forest, spent some little time in discovering its exact location, and at last came upon it suddenly. He showed all the eagerness of a boy as he went through the archway.

"There's the pool," he cried; "that's true; and here sure enough is the sand. You told me it dances every half minute or so; we will not have long to wait."

They sat down a few feet away and watched.

Nothing happened. The pool was still: there was no sign of movement in the sand. Some minutes passed.

"Dreams are queer things," said Heneky reflectively. "Myself I've seen a world of wonders in my sleep."

"But it was not a dream," said Derrick. "Pedro saw it as well as I."

"You made me think I did," said Pedro; "sort of hypnotism, I daresay."

"What rot!" Derrick was a little hipped. "We watched together. You remember how the stream-by the way, where it the stream?"

Except at the pool itself the floor of the cave was dry. There was no longer a gush of water from the fissure in the wall.

"It's certainly very strange," Derrick continued, puzzled. "Why should the stream dry up?"

He rose and scooped up a handful of the sand.

"Look at this," he said to Heneky. "Is there anything peculiar about the sand?"

He poured it into the Irishman's palm. Heneky examined it, stirred it with his finger.

"Quartzite-just common quartzite," he said, and threw the sand into the pool.

Instantly a cloud of particles flew up to the roof.

Heneky jumped up and stood open-mouthed. Derrick refrained from saying "I told you so," and tried not to look triumphant. He took up another handful of sand while Heneky was still gazing at the roof, and cast it into the pool. Another upward shower followed.

"By the powers, 'tis wonderful," exclaimed Heneky. Next moment he started back, rubbing his nose. "'Tis falling again," he said, "but only a trifle: most of it sticks. And to think that I've spent years in these parts and never knew of this remarkable phenomenon! 'Tis a triumph for a tenderfoot, Mister Derrick."

"No Misters here, Pat," said Derrick slyly.

"But now tell me: did you throw anything but sand into the pool?"

"No; it didn't occur to me. But I will now."

He took a pencil from his pocket and dropped it into the water, the other two looking on with keen interest. The pencil sank; but it hardly disappeared from view when it emerged as swiftly as a sky-rocket, and they heard it smack upon the roof. They looked up, expecting it to fall, but it remained as if glued.

"We'll try something else," said Heneky, now all excitement: "something bigger and heavier."

He went to the entrance, and brought from outside a knobby fragment of rock weighing upwards of one pound. On this being thrown into the pool it remained submerged only a second or two longer than the pencil; then, like that, it flew up, struck the roof, and clung. Heneky tried to poke it down with his rifle; but though he brought down a slight fall of sand, the rock refused to be dislodged.

In reaching up with his rifle, Heneky had bent forward over the pool. He was just moving back to the upright position when he uttered a sharp exclamation, and rubbed his cheek, from which the object that had struck him glanced off and splashed into the water.

"'Tis your pencil," he said to Derrick, "and the point—By all the powers!"

The pencil had fallen only to rise again; they could see the gleam of its metal protector in the dark roof.

"Sure 'tis flabbergasted I am," said Heneky. "The water's bewitched. 'Tis plain as the nose on your face that the water has a dislike for solid things; it swallows 'em but can't keep 'em down. Just look now."

He took out of his wallet a small tin mug and dipped it in the water. It was snatched from his fingers, and in a second they heard it clang against the roof.

"It is not water," said Heneky emphatically. "Sure 'tis a spirit. Boys, 'tis a great discovery. We cannot start for home to-night: you and me will stay here till morning. I reckon I'll do a power of thinking before then."

CHAPTER THE SEVENTH - LEVITY AND GRAVITY

THEY ate the food that was left over from their midday meal, and disposed themselves as comfortably as they could for the night. The boys, tired out, slept until dawn. Heneky declared that he had not closed his eyes.

"I could not," he said. "I've been chasing a thought round and round in my head. It is clear as daylight that anything thrown into this water will fly up as long as it's wet. Things stick on this roof until they dry: then they fall again. If there were no roof they'd go up into the air: of course they'd soon dry in this climate. Well now, don't you see here's the making of a tremendous force? I reckon you know all about the force of gravity?"

"Something, at any rate," said Derrick. "It's the pull the earth has."

"You may call it that, but it can be beat: it can be beat. It's beat by the sap of plants: plants spring up in spite of it. It's beat for a moment or two when you jump off the ground: it's beat, just for a time, when you let off a sky-rocket, or fill a balloon with hydrogen gas; it's beat by the internal combustion engine when the aeroplane goes aloft. But it's never been beat as it is by this wonderful water."

"How do you make that out?" said Pedro.

"I'll tell you. I reckon that any object you could keep constantly wet with this water would go up and up, and you couldn't stop it."

"It would fly to the moon?" asked Pedro, rather derisively.

"Why not?-if you could keep it wet."

"That's a very big if," said Derrick.

"Of course it is," said Heneky. "I don't say you could do it. But 'tis only a few years ago you'd have said 'twas impossible for a machine heavier than air to fly. There's no 'if' about that now."

"But I say, Pat," cried Derrick, excitedly, "d'you see what this is leading to? If we could get enough of the water we could fly without an engine."

"And that's the truth's truth. You've heard of these heliocopters they've been trying to make-machines that rise straight up from the ground. Well, there's no need of 'em. We've got the lift in this water."

"It might not be strong enough to lift a heavy machine," Pedro objected.

"Indeed you're wrong. True, we've tried it with nothing heavier than a bit of rock, but if it can lift one bit it'll lift a hundred."

"You don't know that," said Pedro again.

"Your name should be Thomas, my boy. We'll put it to the test. The rock we tried last night weighed a pound or so; come out with me: we'll find a boulder somewhere, and you can help me lug it in."

It was not long before they came upon a heavy mass of rock embedded in earth. They scraped the soil from under it, and found that with their united efforts they were just able to lift it. When it sank with a great splash into the pool the boys scarcely expected to see it again; but a second or two after its disappearance the surface of the water was violently disturbed, the boulder rose as lightly as a balloon, and in a moment it was hanging with a slight swaying movement from the roof.

"Proof enough," said Heneky triumphantly. "We have discovered a new force, my boys, and all we have to do is to harness it."

"The force of levity, Pat?" said Derrick, laughing.

"Ah! You will have your joke. But now we must get back, or the lady will be thinking we're lost, or deserted. Let us fill our water-bottles, and try some experiments at leisure. My name's not Pat Heneky if we don't turn this to some account."

They filled their canvas-covered water-bottles, each holding about a quart, from the pool, then started for home. The return journey was uneventful until they came within a few miles of the Alvarez hacienda. Then, as they halted on the crest of a hill to recover breath after a steep climb, they saw, crossing a ravine a long way ahead, several figures on mules. The riders disappeared almost as soon as they were seen, but not before a gleam of red had caught the observers' attention, reminding them of Juan.

"I wonder if Juan has been to the hacienda to get his pay?" said Derrick.

"I doubt whether he'd venture it," said Heneky, "though these half-breeds, it is true, have a deal of impudence. But any man might wear a red shirt. I'm pretty sure it was not Juan. Bola will tell us."

But when, some two hours later, they reached the hacienda, they found that Bola was absent. Nobody knew what had become of him. Pedro suggested that he had taken French leave, but this Heneky scouted.

"I'd trust Bola anywhere and anywhen," he said. "Maybe he's gone back to the river to get some trifle out of the canoe. These Indians like to have their little things about them."

Late that night, when Heneky was fast asleep in the little room allotted to him at the back of the house, Bola stole noiselessly up through the garden, and aroused his master by putting his head in at the open window and making between his half-closed lips a low sound that could hardly have been distinguished from the cry of a bird. Heneky was awake in an instant. He let Bola into the room, and the Indian told him in murmurs what had called him away.

Early that morning he had noticed a number of strangers lurking in the neighbourhood of the mine. They had not approached the places where the labourers were at work, but had stopped for some time at an outlying part, where one of them a Bolivian señor, had examined the ground with great interest. Meanwhile the three Indians who were with him stood as if on guard. Presently he was joined by a man in a red shirt, whom Bola at once recognised as Juan. The Bolivian was a very large man, and looked a giant beside the stocky figure of the half-breed. They stood for a while talking; every now and then the Bolivian picked up a piece of rock, turned it over in his hand and threw it away or put it into his pocket. By and by they had gone down the hill to a plantation in which they had tethered their mules, and had ridden away. Bola had thought it well to follow them, and had tracked them on foot some twenty miles away to the north-east.

"You have done well," said Heneky. "See that you keep your lips shut. We must not alarm the gracious lady of this house."

Bola gave a low grunt, and returned to his cabin in the grounds to enjoy a well-earned rest after his forty-mile walk.

Heneky kept to himself what he had learned from Bola. He suspected that some mischief was intended, in which the absconded engineer and Juan were concerned; but he had no definite idea of the nature of their purposes, and resolved to keep his own counsel until time and Bola had enlarged his information.

During the next few days Derrick and Pedro with occasional assistance from Heneky when he could spare time from his proper duties, devoted themselves to a course of experimenting with the water brought from the pool. They had so small a quantity of it, and it was so liable to evaporation in the heat of the day, that they conducted their experiments at first on a small scale. But they were able to arrive at certain definite conclusions which Derrick tabulated in a memorandum, as follows:

(1) Any body surrounded by a film of the water tends to move upward.

(2) The rate of motion upward is inversely as the mass of the moving body.

(3) The upward movement ceases as soon as the continuity of the film is broken.

(4) The water when evaporated leaves a slight deposit.

(5) This deposit is readily soluble in water, and the new solution has the same properties as the old.

"Sure and that's methodical entirely," said Heneky when he read the memorandum. "They are facts, every one of them; and now what theory do ye deduce from them?"

"I haven't really thought about theory," said Derrick. "The facts are good enough."

"But facts without theory are like food without digestion. I'll tell you what I make of it now. Matter attracts matter-everybody knows that; but can you tell me why? You cannot. Everybody knows, too, of the phenomenon of repulsion in electrical currents. Well, here we have a condition in which matter repels matter, and 'tis my belief it's electrical."

"Not chemical?"

"No: because there's no chemical change of state. There's no reaction. The sand you send sky-high remains, sand; this alkaline solution remained just as it was. 'Tis not like when you throw water on to lime: there's no smoke or heat. I believe the solution somehow or other changes the electrical state of whatever solid body is immersed in it, though I own I cannot explain why it sends the body aloft, and indeed neutralises the force of gravity."

"After all, Pat, it's the practical effects of our discovery that matter. What use can we make of it?"

"That we will see before we are many days older. Go on with your experiments. Here's a suggestion for you. So far you have only put solid bodies into the, water. Now try something hollow."

"Do you happen to have a rubber ball anywhere on the place, Pedro?" asked Derrick.

"There may be one that I played with as a kid. I'll see."

Pedro went into the house, and soon returned with a rubber ball about three inches in diameter. Upon this being immersed in a bowl of the water it flew upward with tremendous velocity, almost disappearing from sight. In about half a minute it began to fall, and when it came to earth, and was retrieved, it was quite dry.

"If I'm right," said Heneky, "there's no reason why that ball should fall at all could we only keep it wet."

Pedro laughed incredulously.

"Well, let's try," said Heneky.

He took from his wallet a rubber bag in which he was accustomed to keep things that he wished to preserve from damp. Into this he poured enough of the water to submerge the rubber ball.

"Take a hold of it," he said, preparing to drop the ball in, "or it'll fly off before I can close up the bag."

The boys had to exert considerable force to hold the bag upon the ground while Heneky tied up its mouth.

"Let go," he said.

The moment they lifted their hands the bag rose vertically as a bubble rises through water. It soared up and up, diminished to a speck on the sky, and finally disappeared altogether.

"Well, I'm jiggered!" ejaculated Pedro. Heneky's face beamed with delight.

"You and me will be flying to the moon yet," he said. "With enough spheres, and enough of this water to cover 'em, and some device for preventing evaporation, and a few other trifles, we could lift a machine miles high."

"What about atmospheric pressure, rarefied air, intense cold and all that?" said Derrick.

"Trifles-mere trifles, my boy. There's nothing that cannot be got over if you have a mind to it. But we'll not lose our heads. We'll go slow and make every step sure before we take the next. I must get back to the mine now, but I'll put on my considering cap to-night, and to-morrow we'll go a bit farther."

At breakfast next morning it appeared that the night's cogitation had brought both Heneky and Derrick to the same conclusion. Pedro, for his part, owned that he had not thought of the matter; he took up the attitude of a rather amused, rather sceptical spectator. Before any more elaborate experiments could be conducted, a much larger supply of the water was necessary. A good deal of the small quantity they had brought from the pool had been lost; and though they had retained as much as possible of the alkaline crystals that remained after evaporation, even these showed a sensible diminution, and Heneky was not yet sure that they would keep their virtue after an indefinite number of fresh solutions had been made.

It was arranged that during the day Derrick should ride to the cave on mule-back under Bola's guidance, the mules being loaded with some large skins capable of holding several gallons of the water, and also with a couple of shallow pans which, when filled with the water, could be left in the open, exposed to the full rays of the sun. Evaporation was so rapid that probably in the course of twenty-four hours the crystals would be left dry in the pans; they could then be carried to the hacienda and kept as a reserve.

"And then what we need is a balloon," said Heneky: "one that could be lifted, not by gas but by things steeped in this water."

"I could make you a small balloon out of silk," said Señora Alvarez, who had begun to take a serious interest in the experiments.

"Indeed you could, ma'am," said Heneky, "but I do be thinking of something big enough and strong enough to lift a man."

"Surely you won't risk your bones?" said Pedro. "Well now, I would not presume to make a voyage to the moon without a trial trip. For a beginning it would be enough to be lifted two or three feet off the ground, and then if I did fall, my bones would still hold me together. Would you give me leave, ma'am, to take a look around your property, and make use of anything that would serve the purpose, provided I did not damage it?"

"Certainly," said the lady. "And if I can give you any help I shall be glad."

Derrick and the Indian started early, made quick travelling and reached the cave on the second day. After filling the water-skins and pans Derrick plumbed the pool with a sapling, and found that it was between four and five feet deep. Evidently it would not last long as the sole source of supply, and Derrick saw with concern that the stream which had fed it through the fissure bad not resumed its flow. It seemed probable that this stream carried with it particles of the alkaline salts in its passage through the rock; there must be a considerable deposit of those salts somewhere: they might be close to the surface, or brought from a depth by a spring, and if that spring had dried up, a serious problem would arise. The fissure was too narrow for a man to enter; it would be necessary to cut back the rock in order to find the position of the deposit; and Derrick chafed at the idea of spending time in a kind of mining operation.

When he got back to the hacienda he found Heneky showing off with a childish delight to his aunt and cousin the experimental balloon which his ingenuity had contrived.

"Come and look, Derrick," said the señora; "we were only waiting for you to return. Pat is a wonderful man."

"Just an Irishman, ma'am," said Heneky soberly.

"And what do you think of it, my boy?"

Derrick saw a large fishing-net stretched over a light framework of cane, which shaped it like a balloon. At the neck it was firmly fastened to a strong wicker basket, large enough to hold a man. In the bottom of the basket lay a pan.

"A very good makeshift," said Derrick. "It didn't occur to me that the material of our balloon need not be air-tight, but of course we have no gas to keep from escaping."

"And our lifters will not pass through the meshes," said Heneky.

"What are they?"

"These gourds grown on the estate." Heneky pointed to a number of melon-shaped fruits lying on the ground. "Now I'm on thorns till we try the contraption. Pour into the pan enough water to cover the gourds, then I'll drop them in, and we'll see how many are needed to lift this balloon."

"Hadn't you better tie on a cable, in case your balloon floats right away to the moon?" suggested Pedro in a chaffing tone.

"'Tis you that's the practical man," retorted Heneky. "I would not like to lose it after all the trouble I've taken, so we'll keep it under control."

He fastened to the basket a stout cord several yards long. Then, the pan being half full of water, he dropped in one of the gourds. As soon as it was thoroughly immersed it rose rapidly through the neck of the balloon to the network at the top. Heneky threw in two more gourds in quick succession, and with the rise of the third, and a slight upward push, the basket was lifted several inches off the ground. But after a very few seconds one of the gourds fell, hit the rim of the basket, and bounced to the ground. At the same moment the basket sank. Pedro smiled.

"The gourds are too big," said Heneky. "They dry too quickly. We need something smaller."

"Grape fruit?" suggested the señora.

"The very thing! Small ones, if you please, not above the size of oranges."

"And have you got a syringe, Aunt?" Derrick asked.

"Yes, I will send for it."

"Why do you want a syringe?" asked Pedro. "To spray the fruits with the water when the balloon goes up."

"You can't do that unless you go with it."

"That's what I propose to do-squat in the basket."

"Sure and you're the broth of a boy," said Heneky enthusiastically. "I'll keep a hold of the guide rope, so as you will not leave us before your time. We cannot afford to lose ye."

The servant despatched by the señora soon returned with a large garden syringe and a dozen firm round fruits. In the basket a pail was substituted for the pan, to make room for Derrick. He sat there with his knees up: the fruits were dropped into the water, and flew up as the gourds had done. Six had risen; there was still no indication of buoyancy.

"You're too much of a lump, Derrick," said Pedro.

But with the seventh there was a slight tilting movement of the basket; the eighth raised it an inch or two from the ground; and with the tenth the strange-looking contrivance rose still higher and began to float along on the wind. Heneky, cord in hand, followed it, smiling all over his face, as Pedro said. Meanwhile Derrick diligently sprayed the yellow balls above his head, getting well drenched as the water fell back upon him, and it was only when the contents of the pail were exhausted, and the fruits one by one dropped, that Heneky ceased to feel the upward drag on the cord, and the balloon sank gently to earth.

"Now what do you say, you doubting Thomas?" cried Heneky, with a triumphant grin.

"I give in," said Pedro. "You've done the trick."

"Trick! Sorra a bit of trickery about it," said the Irishman. "We've solved a problem: we've discovered a new force; we've a means of aerial flight beyond anything that's ever been known, and faith! before many days are gone we'll learn how to use it. Hurroosh!"

He flourished his arm round his head as if wielding a shillelagh.

"My dear boy, you're all dripping wet," said the señora to Derrick. "Run in and change. Tea will be ready at once. Will it be necessary to get drenched every time you try your experiments, Pat?"

"'Deed it will not, ma'am." said Heneky. "Besides, it's a terrible waste of the water. 'We have only just begun."

CHAPTER THE EIGHTH - FIRST STEPS

AT breakfast next morning Heneky wore a very sober look. He responded gravely and without his usual smile to the greetings of the others. "Got a pain, Pat?" asked Pedro.

"I have not," was the reply.

"I hope you hadn't a bad night," said Señora Alvarez sympathetically.

"I had not, ma'am," said Heneky. "I had a very good night, because I figured out two-three problems arising out of our discovery—or rather Derrick's, for I had nothing at all to do with it-and 'tis now all clear in my head."

"You didn't get much sleep, then?" said Derrick.

"It might be an hour."

"That's too bad," said the lady.

"It is indeed, ma'am, for I doubt I'll not earn my wages. You engaged me to help with your mine, but my unruly thoughts run other ways."

"Let us hear these unruly thoughts of yours," said the señora, smiling.

"Well, then, you shall, ma'am. First and foremost, the source of this new power is in that cave, and nowhere else so far as we know. If we're to turn it to account we must get possession of it. I say we, but 'tis Derrick must be the owner."

"Oh no," said Derrick. "It is true I first noticed the phenomenon, but Pedro was with me at the time, and if you hadn't found us and shown us the way home we should very likely have starved in the forest. If there's any question of ownership we must go shares, all three."

"Leave me out," said Pedro. "I did absolutely nothing."

"Don't let's argue about that," said Derrick. "I want to hear what else Pat has in his head. Go on, Pat."

"You must get possession, as I said," Heneky went on. "And that means you must lodge a claim, with a map showing how many estradas you want. There's no one in before you, so far as I know; the district is unexplored; the Government will grant your claim, and the place will be yours for a small rent-a mere trifle."

"That's the law, is it?" said Derrick. "Well, it won't be difficult to make a map; I suppose all the ground we want doesn't extend to more than an acre, and very little detail is needed. The claim must be lodged at La Paz, I suppose?"

"It must. And it must be registered in your name." "You come back to that again. I stick to it that we're all three concerned, and if any commercial benefit results, we'll go shares."

"You excite me," said the señora. "Do you think of collecting quantities of the powder, or whatever it is and selling it? How will you decide on a price?"

"Indeed we'll not sell an ounce of it," Heneky broke in. "What we've to do is to get a machine built, and keep our power a secret. I know the name of a good firm in Coventry."

"But we should have to give them a specification to work to," said Derrick.

"I'd draw one up in the light of our experiment with the net yesterday."

"But wouldn't that give the whole show away?" Derrick objected again. "The machine would be so much unlike anything ever made before that it would arouse curiosity. We mustn't give away our secret."

"Then we come to a full stop," said Pedro. "Not that it matters to me, for in any case I'm out of it."

"Not at all. This is just where you come in. If Aunt Bertha is willing we'll build a machine here."

"How in the world? We've no designer, or draughtsman, let alone materials."

"Indeed that last is the only thing that's bothering me" said Heneky. "In the night I figured out a design but as we would need steel plates and haven't got any, I saw no way, except to send to Coventry."

"I did a little figuring out, as you call it, too," said Derrick with a smile. "What about the steel plates of the broken trucks?"

"Glory be!" cried Heneky, his eyes gleaming. "Sure that's the way of it, and why didn't I think of it myself? There's the broken trucks, and the crumpled tank-all the steel we need; and the engineer's workshop escaped the landslide; there's tools in plenty—"

"So that all we're waiting for is your permission, Aunt," said Derrick.

"Begin at once, and good luck to you," said the señora. "I make only one stipulation."

Heneky looked at her a little anxiously, but was reassured by a twinkle in her eye.

"And what is that, ma'am?" he asked.

"That when you have built your machine, you take me up for a flight."

"Sure that will put heart into us all!" cried Heneky. "'Tis you that believe in us, and we'll work all the better for it. You shall be our first passenger, ma'am, as soon as we've proved it safe for a lady."

"You won't break any men's necks in proving it, I hope," said the señora, laughing. "Seriously, I am sure you will succeed, and I shall be quite impatient for my first trip in the air."

As soon as Heneky had set the mine labourers their tasks for the day, he drew Derrick into consultation about the form the proposed machine was to take. Heneky had a fund of experience of various kinds of engineering. Derrick was fresh from a year's study in a technical college; but as their discussion proceeded they recognised and deplored the many gaps in their equipment as constructors. At every turn they were confronted with problems: "If only I had inquired into this," Heneky would remark; or Derrick: "If only I had gone more carefully into that!" It was fortunate that Heneky had made a hobby of the aeronautical journals. He had picked up a good miscellaneous knowledge of the essential conditions of aerial flight, and much information about the latest developments in aeroplane construction. Derrick's contribution to their joint efforts consisted chiefly in a theoretical knowledge of mechanics and a quickness of resource. If they were baulked by a difficulty, he was always ready with alternative modes of overcoming it.

The starting-point of their work as designers was the essential difference between the proposed new machine and other machines heavier than air: it needed no engine. This greatly simplified the problem of lifting power. Under the impulse of the new force the machine would rise directly from the ground, whereas an aeroplane can rise only by the conversion of the horizontal force generated by its powerful engine into a partly vertical force by means of its planes. The problem before Heneky and Derrick was how to convert the vertical force that lifted their machine into a partly horizontal force. Obviously this could only be done by an arrangement of planes, and of course movable control surfaces would be needed for manoeuvring the machine when once it was aloft.

The first point to be determined was the shape of the machine. Heneky's experiment with the net inclined him towards the balloon-shape, but Derrick suggested that as the machine's movements in air would correspond in some respects to the movements of a submarine in water, a more fish-like form would be preferable. He made a rough drawing embodying his idea.

"Very like a whale," said Pedro, who had come in to see how the others were getting on. "What are the fins for?"

"They are planes for ensuring a certain stability, like the fins of a fish," replied Derrick. "And here at the tail, you see, are vertical and horizontal rudders, or rather rudder and elevator. It's only a rough sketch, of course; but I think it shows the most likely external appearance of the machine."

"It does that," said Heneky, "but sure 'twould weigh thirty tons and take a year to build; indeed, I doubt whether we'd build it at all; we have not the materials or the appliances. We need something smaller and lighter, that will suit our steel plates. Try again, my boy."

Derrick made other attempts, altering here and there as Heneky suggested. In the end he produced a design which the Irishman thought suitable to the three-sixteenth-inch steel plates available. Drawn to scale, the machine was a little more than twenty feet in length; the diameter amidships, where it was circular, was six feet six inches; and the total span of the planes was seventeen feet.

"Won't you want some sort of an undercarriage to take the shock of landing?" said Pedro.

"We shan't need one," said Derrick. "We can manipulate the force so as to come down as gently as you please."

"But if you come down from a great height, won't you come an awful whacker?" Pedro persisted.

"True, if we can't control the machine," said Heneky. "We might come down with a landing speed of something like two hundred and fifty miles an hour, and an undercarriage would be no more use than nothing at all. In any case, the ordinary type of wheel undercarriage would be no manner of use in this rocky country. Still, you can have some landing skids if you like as a bit of an ornament. Draw a pair, my lad."

"I don't see at present what practical use the machine will be," said Pedro. "You don't seriously think of a trip to the moon, I suppose? Well, what's the good of going up and up?"

"This is the way of it," said Heneky. "With the elevator and the rudder we can fly any way we please. Furthermore and besides, we can rise to a greater height than any aeroplane ever did yet, and then if we shut off the power we can come down at a tremendous speed. There'd be plenty of space, you see. Not that we'd want to come straight down, by the token; we'd make a long glide."

"But you can't breathe at a very great height: you perish with cold; your arteries burst, don't they?"

"Trifles, my boy. How do they manage with a submarine? They make it water-tight, and carry their own air. We'll do the same. We'll make our machine airtight, and carry something in the inside of it to keep us warm."

"Make a sort of thermos flask of it," said Pedro, smiling.

"I wouldn't wonder," said Heneky. "Believe you me, we'll attend to all these details, and you cannot expect us to do it all in a day. Here we've got a likely design for the outside of the creature, and now we must just work to it."

Having decided not to begin the actual construction of the machine until they had canvassed all the problems likely to arise, Heneky and Derrick devoted a good many hours to the patient consideration of details. To guard against cold, they decided to construct an inner lining to the outer shell, and to fill the space between them with a quantity of asbestos packing which they found among the stores. As it would, of course, be necessary to see out of the machine, and to obtain a good view in all directions, they asked permission of the Señora Alvarez to remove some of the plate glass windows of the hacienda, with which to form small windows, about a foot square, in the framework of the hull. Embedded in indiarubber, the glass, consisting of several thicknesses fused together and bent at the same time to the required shape, was, they thought, capable of resisting any pressure that might be encountered at the great speeds they hoped to attain.

When they were satisfied that no contingency had been overlooked, they started active work. For the next few weeks there was almost constant hammering in the large shed that constituted the workshop of the mine. The first step was the dismantling of the broken trucks; the next was to mould and rivet the steel plates and framework so as to form the hull of the new machine. This was done under Heneky's supervision on a staging such as would have been used for the construction of a small yacht. The native labourers took kindly to their new job. Among them were some who showed considerable mechanical aptitude and dexterity, which was not surprising, seeing that mining has been carried on in Bolivia for hundreds of years, and the men have gained a certain familiarity with mechanical appliances. They were not informed of the purpose of the new machine, and exhibited a naive curiosity regarding it.

One of the greatest difficulties of the builders was to get a perfectly smooth and clean exterior for their hull. When the plates had been riveted together, Heneky set the unskilled men to scrape and polish, and this work was carried on while the more skilled were fitting up the interior.

The most important problem in the internal arrangements was the application and control of the force of levity, as they had agreed to name the new force. As the result of their experiments with the grape fruits, they had decided that the necessary lifting power could best be provided by a large number of small spherical bodies. Heneky therefore set two men to work at the lathes, turning several hundreds of wooden balls three inches in diameter. As receptacles for these, he had constructed in the roof of the machine, above the centre of gravity, and extending some distance fore and aft of it, five small steel compartments, rigidly connected to the main frames of the hull structure. Each of these compartments communicated with a small tank, from which it could be supplied very rapidly with the alkaline solution by a forced feed, and which could itself be replenished from a larger tank in the floor of the machine. The compartments could be flooded consecutively or simultaneously, and outflow pipes were made, so that the water, having fulfilled its purpose of thoroughly wetting the balls, might drain back into the lower tank.

Since there would be very little evaporation within the enclosed vessel, and the balls would remain wet, and therefore retain their lifting power for a long time, it was necessary to provide a means for drying them very rapidly, so as to ensure descent at the will of the operator. They had no water-attracting chemicals at hand; and it was only after much consideration that Derrick hit upon a promising device. It was an ascertained fact that unless a body was completely surrounded by the fluid, it ceased to have any lifting power. On the other hand, it retained that lifting power, however thin might be the film of liquid enclosing it. Acting on this, Derrick bored in the upper half of each compartment a number of small holes through which air could be forced under pressure. He found on trial that the jets of air, impinging on the balls nearest to the holes, almost instantly dried off the liquid on the parts which they struck, and the balls lost their upward thrust, dropped, and were replaced by balls still wet, which in their turn were dried, or "delevitised," as Derrick put it. Further experiment proved that all the balls in a compartment could be treated in about five seconds, and as all the compartments could be dealt with simultaneously, the machine could be deprived of its ascensional force, and restored to the normal action of gravity, within the same period.

It took a great deal of thought, and the drawing of many plans, before Derrick and Heneky between them decided on the means of operating the machine. Here Heneky's hobby served him in good stead, as he had mastered the smallest details of every technical point, in the art of flying, which he had come across.

The effects of the absence of an engine and the introduction of the new force of levity had to be taken into account, as they at once simplified and complicated the design. After some deliberation he concluded that the problem of lateral control, which he had learned to be of such vital importance in an aeroplane, was greatly simplified by the fact that the lifting force was, in the main, obtained not from the wings, but from the levity cells in the hull itself. The lift of the wings would only be used when they had climbed to the desired height and shut off the levity on the downward glide.

From this he deduced that whenever the levity was operating, the machine would possess natural stability, like a ship floating on the water, and would thus right itself if disturbed. Thus lateral control need only be considered on the glide, and the use of ailerons could be dispensed with, by setting the wings at a dihedral angle.

Derrick was beginning to get out of his depth by this time; Heneky's fund of knowledge of the air and its mysteries seemed to take him on to another planet. "Whatever is a dihedral angle?" he blurted out at length, unable to restrain himself any longer.

"Well, this is the way of it. You've seen the vultures soaring over the mountains up yonder, circling round for hours on end, without moving a feather? They can only do that by setting their wings at a dihedral angle; that is, instead of their wings being stretched out straight, you'll see, if you look at 'em head-on, that the wing-tips are turned upwards slightly. Now, does a gust of wind strike one wing-tip, tending to roll 'em over, the dihedral angle brings 'em back on to an even keel."

"Sounds a bit mixed, Pat."

"Maybe, but it gives you my meaning. And there's more to it. When they're turning in small circles, they must bank over, same as you do going round a corner on a bicycle, and the upturned wing-tips bring them on to a natural bank, or sure they'd slide outwards, or skid. Well now, we can get inherent lateral stability in this way, and so we can do without ailerons entirely, and our control mechanism is as simple as A B C."

They realised that they would have some difficulty in obtaining freedom from leakage to the outer air, where the elevators and rudder were attached to the hull, and eventually they decided that the simplest plan would be to fit an airtight bulkhead forward of the tail-planes, so that the part of the hull aft of the bulkhead was open to the outer air. The tail controls were passed through stuffing boxes, or glands, in the bulkhead, to the pilot's seat in the nose of the machine. Here they were connected to a wheel and column, the wheel acting like that of a motor-car and operating the rudder, while the fore and aft movement of the control column upon which the wheel was mounted turned the elevators up or down.

"We will have to rely chiefly on the levity," remarked Heneky, "to alter our trim fore and aft, only using the elevators for small momentary adjustments, when diving or landing. That's why the levity cells extend some way for'ard and aft of the centre of gravity. When we climb and the levity is going full out, the centre of gravity must fall beneath the centre of lift so that it sets us automatically on our angle of climb. When we cut off the levity and dive down to Mother Earth again, and the wings so a bit of lifting, the machine will automatically adjust itself to its natural gliding attitude.

"The thing we will have the most trouble with is landing. We will have to practise 'landing in the air!' so to speak, until we get the hang of it. As I figure it out, we should switch on not quite enough levity, in the front cells, to prevent us sinking, and to tip the nose of the machine up so that we don't turn a somersault on landing. That's where we will need a power of practice, and after we've got the knack of it, we can float down like a feather. It beats the aeroplane to a frazzle, and combines all the points of the aeroplane and the airship, without any complicated engines to go wrong."

The valves for admission of the water and air to the levity cells were worked by foot pedals, whilst a number of triggers on the handwheel provided for a more precise variation of the supply, as between one cell and another.

"Then there are the pumps; you've used up all the pilot's hands and feet. I suppose he works these by waggling his ears," chaffed Derrick.

"Sorra a bit! That's where you come in. It's all of one man's work to control the machine, without having to do the donkey work. We'll fix the pumps up further aft, and you'll be the donkey engine!"

There remained the problem of air supply. Since the root idea of the invention was to make very rapid ascensional flights to great altitudes, and then to descend under the action of gravity, the makers did not aim at remaining for long periods in the higher regions where breathing would be impossible or difficult. The vessel was of sufficient cubical capacity to hold air enough for their normal needs at the highest altitudes. But in order to ensure a change of air at lower altitudes they decided to place an outlet valve in the roof, just in front of the bulkhead, to carry off the used air by suction, and to insert in the forepart a tube through which fresh air might enter as the machine flew. Either could be closed at will, and they calculated that during the few minutes when the machine would remain in the higher regions of the atmosphere, it would contain enough pure air to last out until it once more descended.

These details were of course not settled all at once.

They were decided as the result of many consultations, often prolonged for hours. Heneky's principle was to tackle each problem as it arose, and he more than once warned Derrick that when they came to attempt a flight they might discover that some vital point had been overlooked. But he promised Señora Alvarez that they would subject the machine to thorough tests before setting out on a serious flight.

"We'll walk before we run, ma'am," he said reassuringly.

CHAPTER THE NINTH - MOLLENDO'S FIRST FLIGHT

THE actual construction of the machine was done by the skilled mechanics of the mine under the supervision of Heneky, and according to the plans carefully drawn by Derrick. While this practical work was going on there were times when Derrick would have been unemployed but for the necessity of carrying out Heneky's scheme for obtaining legal possession of the cave. He made several visits to the spot in company with Pedro and Bola, partly for the purpose of getting a supply of the crystals left by evaporation of the water from the pool, partly in order to prepare a large-scale map of the district. When this was finished, it was sent to La Paz with instructions to the Señora Alvarez's lawyer to deposit at the Office of Mines a formal claim in the name of Pedro Alvarez, with the alleged object of prospecting for minerals in the district covered by the map. The payment of a small initial fee on registration would secure their position if the land was Government property, and if there was no prior claim, a contingency that seemed unlikely.

The main road to La Paz being still blocked by the landslide, the messenger, a trusty native servant of the señora's, had to follow a roundabout route through the hills, and it was expected that a considerable time must elapse before he could return, bringing the official receipt and the stamped authorisation to work the specified district. This interval was utilised for making a more thorough examination of the cave. The spring that fed the pool had ceased to flow, and there seemed no possibility of tracing its source except by laboriously cutting away the solid rock on each side of the fissure, an operation that would have taken a longer time than Derrick cared to contemplate. From indications in the soil of the cave he came to the conclusion that the spring had flowed only for a short period, and it seemed likely that the fissure through which it entered the cave was itself a result of the earthquake which had shaken the country a few months before.

Evaporation of water from the pool had left a deposit of greyish-white crystals, and Derrick, remembering that he had first noticed the lifting phenomenon when water flowed into the bed of sand, suspected that the sand contained a large admixture of the crystals. He collected a small quantity of it, put it into a pan, and poured in water. As soon as the crystals had sufficiently dissolved, the sand rose out of the water and was wafted away by the breeze. Then, evaporating the clear liquid left in the pan, Derrick obtained a considerable quantity of the strange substance.

"We ought to have this analysed," he said to Pedro.

"I wouldn't do anything of the sort," Pedro replied. "If the chemist finds out its constituents he can probably make it artificially-synthetically, as they say; and then we should lose our monopoly."

"All the same, I'd like to know. However, the great matter is that there seems plenty of the stuff, and we shall get more by washing the sand than by evaporating the water from the pool. We ought to lay in a good stock, for we don't know yet how long the crystals retain their virtue. Possibly they lose their power after repeated solutions. In any case there must be a good deal wasted, and we mustn't run short."

"It will take a long time to get the crystals in large quantities by this slow process."

"But there's no other, as far as I can see. And as it would be very laborious to carry loads of the sand to the hacienda, we had better bring over a few men with more pans, and take back only the crystals we obtain."

"Don't you think that the fewer we let into the secret the better?"

"Certainly; but your men have already seen something of our experiments. You can't send things flying sky-high without being noticed. They don't know how it's done, and I doubt whether they'll connect these crystals with it; they'll more likely think we are testing a new mineral. Anyhow, we'll see what Heneky says."

What Heneky said was that instead of bothering about things like that, they ought to have pegged out their claim.

"Nobody else is likely to come prospecting in such a remote spot, in the midst of a jungle," said Pedro. "Besides, the map has gone to La Paz."

"To your first I say you never know," replied Heneky. "To your second I say you should always make your boundaries clear. What a lot of disputes and wars have arisen between countries because of uncertain boundaries! We've got a copy of the map, and you'd better go to-morrow and drive pegs in around our plot."

"Won't you come too?"

"I doubt whether I can leave the machine, but maybe I'll come and inspect."

Next day Derrick and Pedro set off early with Bola and another Indian, all riding mules. They carried hatchets and hammers; the wood for the pegs they would find in the forest. The two cousins had their rifles, without which, indeed, they never wandered any great distance from home: there was always a risk of meeting wild beasts or savage Indians. They were provided also with food sufficient to last two or three days.

On the afternoon of the day after their arrival, when enough pegs had been cut for staking out their claim, they were resting and taking a light meal near the cave when Bola suddenly turned his head to the west, held up his hand for silence, and after sitting for a few moments in a rigid attitude of attention, got up and disappeared quickly and silently among the trees.

"What remarkable hearing he has!" said Derrick. "I suppose it's Pat coming."

"Not from that direction," said Pedro. "It's probably an animal."

Only a minute or two had passed before Bola returned. He said a few words in his own tongue to Pedro.

"Six strangers are coming this way," Pedro translated to Derrick: "two señors and four Indians." He rose to his feet.

"Don't do that," said Derrick. "Sit down again. I don't suppose they have anything to do with us, and in any case we mustn't show concern."

"All the same, have your rifle within reach," said Pedro, sitting down again.

Bola had resumed his place beside the other Indian, and squatted motionless, his keen eyes fixed on the trees opposite.

In a few minutes two men on mule-back appeared.

The first was dressed in a semi-military uniform; a long black moustache curled on his upper lip.

"An officer of gendarmes," whispered Pedro.

His companion, in the ordinary civil costume of the country, drew the boys' more particular attention. His huge frame looked too bulky for his mule, and his snub nose too small for his fat cheeks. He had thick lips, an enormous jaw, and several chins. His complexion was as swarthy as an Indian's, and his small moustache was intensely black. Behind the two rode four stolid Indians.

The newcomers halted for a moment at sight of the seated party; then the two señors advanced, the officer saluting, the large man sweeping off his spreading Panama, and disclosing a dome-shaped head, quite bald.

"Good-day, gentlemen," he said in Spanish, throwing an inquisitive look, first at the persons he addressed, then at the cave behind their backs.

The boys rose to their feet, Pedro suitably responding.

"It is charming to meet gentlemen in a so out-of-the-way spot," the stranger went on. "One looks for beasts, certainly; for Indians, perhaps; but for gentlemen-no; it is unexpected: it is a pleasure."

Derrick had picked up a little Spanish since his arrival, and was able to make out the gist of what the stranger said.

"You are very good," said Pedro politely. "Are you travelling far? Can we assist you?"

"We have come far, indeed, but this is the end of our journey. I have come in company with Captain de Silva to take possession of a mining claim."

"Indeed, sir," said Pedro. "It is registered?"

"Yes, it is duly registered with the Bolivian government. And remarkable to say, this very pleasant meeting takes place on ground that is included in my claim. Still more remarkable, some kind person has already cut pegs, I see; that will save my Indians much labour." He glanced at the pans in which the sand had been washed, but said nothing about them.

Pedro was rather quick-tempered, and Derrick, guessing by the look in his eyes that he might blurt out something which would lead to trouble, said under his breath:

"Steady, old chap. We're in the right."

"I fear there is some error, señor," said Pedro quietly to the stranger, who had meanwhile ponderously dismounted. "We cut these pegs for ourselves. We have the mining rights over a small area here. Our claim was registered in the office at La Paz some time ago."

"The error is on your side, señor," insisted the stranger blandly. "We have come directly from La Paz. I myself personally examined the register; it was an obvious precaution, for naturally one would not claim ground that had already been appropriated to another. Most certainly there was no prior claim, and I have here the official permit to start operations."

He took a document from his pocket, and displayed the official seal.

"It is possible that your claim is to an adjacent site, not actually to the ground we are standing on," said Pedro.

"Not so," said the man, diving into another pocket, and bringing out a map which he proceeded to unfold. "You see here is the outcrop of rock, marked with a thick black line; here is the enclave which we may call a cave; here is the surrounding forest. You will perceive that the spot on which we are holding this interesting conversation is the very centre of the area mapped. I repeat, the error, señor, is yours."

The boys were puzzled, nay, astounded as they examined the map which the man held before them. Except that it was more roughly drawn, and that the few words upon it were Spanish, and not both Spanish and English, it was identical with the map upon which Derrick had spent such pains weeks before. The stranger smiled as he marked the expression of their faces.

"You are, in fact and in law, trespassers," he went on in the same bland tone, which they began to find annoying. "It is in ignorance, I am sure, and I should not dream of ousting you from a temporary encampment. But you clearly understand that it must be temporary; that you are here on sufferance. And if, as I suppose, you have started washing the soil, that must cease."

He folded up the map, replaced it in his pocket, and walked towards the cave, as if intending to leave the boys to digest his words. They looked blankly at each other.

"What's the meaning of it?" said Derrick.

"Goodness knows! Sharp practice of some sort."

"That's a copy of my map. I could swear it."

"Some official at La Paz has given us away. They're a venal lot."

"But what does he know about the place? Why should he think it worth exploiting? I'm sure he's never been here before. Look at him! He's not going into the cave in the way of a man who knows it."

The stranger had in fact stopped at the entrance, looked curiously at the archway, and gone in with the slow and careful movements of a man who is feeling his way.

A movement among the Indians attracted the boys' attention. Looking round they were delighted to see Heneky walking towards them. The Irishman glanced at the strange Indians, gave one hard look at the Bolivian captain, then passed on.

"What's this?" he asked quietly.

"Our claim's jumped," said Derrick. "I can't understand it, but someone has registered first."

"This policeman?"

"No: a fellow who's just gone into the cave. He's got a map that's cribbed from mine."

"You're telling me! I'll be after casting my eye on the creature."

He went on to the cave, the boys following him.

The Bolivian captain sat his mule with an air of indifference. Heneky entered the cave just as the stranger was turning to come out. The sunlight struck full upon his face. Then the boys were astonished. Heneky strode forward, his features working with suppressed passion.

"So, Miguel Mollendo, we meet at last," he said in a tone low but vibrant with intense feeling.

The Bolivian's swarthy cheeks paled, his eyes quavered, his massive jaw appeared to drop. But only for a moment; with a manifest effort he collected himself.

"You have the advantage of me, señor," he said. "My name is not Mollendo."

"I know you for a thief, Mollendo. I suspect you to be a murderer. Mollendo. You are also a liar, Mollendo."

The man's cheeks flushed a fiery red. His hand moved towards his hip pocket. The boys had already had occasion to marvel at Heneky's extraordinary rapidity of action in emergency, contrasting with his usual deliberateness of movement. His fist shot out. It caught Mollendo squarely under his multiple chin, and the big man was hurled backwards into the pool. As he fell he muttered one loud cry for help. The captain flung himself from his mule, drew his revolver, and calling on the Indians to follow him, rushed into the cave. But even as he crossed the threshold he was staggered into quiescence by an extraordinary sight. For the moment Heneky and the two boys were equally astounded. Out of the pool shot a huge form. It struck the roof with a resounding smack. And there Miguel Mollendo stuck spreadeagled like a gargoyle on a church tower.

CHAPTER THE TENTH - QUESTION AND ANSWER

THERE was an interval of absolute silence. Even those who were acquainted with the expulsive power of the water had never contemplated its direct action on a human being, and the others stood as though spellbound in a petrified amazement. Then the captain hastily crossed himself with the hand unoccupied by his revolver, and shrank back, still fixing his fascinated eyes on the big form spread out above. The Indians, close behind him, broke their silence with a howl of terror, and fled helter-skelter. Bola threw one contemptuous glance at his frantic fellow-countrymen; then resumed his usual pose of stolid impassivity, with one eye, however, alert to catch any sign of offensive movement on the part of the Bolivian gendarme.

Heneky's expression was too much for the boys.

After the first moment of astonishment they had with difficulty repressed their laughter: the contrast between the Irishman's grimly set lips and his twinkling eyes overcame their restraint. But they became grave again when Mollendo, whom the shock had deprived of speech, suddenly found his voice. He had been carried face upward to the roof, and apparently the protuberance of his person, acting as a buffer, allowed him breathing space. In broken accents that betrayed hill terror he called upon the captain for help. But the captain was shaking with the fear of black magic. Mollendo ejaculated a frenzied appeal to Heneky, scarcely articulate.

"You are there: why not stay there?" said Heneky. "He'll come down when he's dry," he added under his breath to the boys. Then, bethinking himself, he addressed Mollendo again. "Answer me some questions, and see that you tell no more lies."

"Yes, yes," gasped the man.

"Your name is Miguel Mollendo?" "Yes."

"You accompanied me and José Gomez on a prospecting trip seven years ago?"

"Yes."

"You stole the gold we discovered, bribed our Indians, and bolted?"

There was a pause, a groan.

"Come, answer, or—-"

"Yes, yes," cried the man, and groaned again.

"After you had murdered our companion," Heneky went on, with deliberation and emphasis.

"No, no," shrieked Mollendo. "It is not true: it is not true."

Heneky seemed surprised.

"Are you lying now?" he said. "No: I swear it."

"Then what became of him?"

"I do not know. He disappeared. Ay de mi, ay de mi! What will become of me? Help!"

For a few moments Heneky kept silence, looking thoughtfully at the man suspended three or four feet above his head. Then he appeared to make up his mind.

"It may be the truth," he muttered, adding aloud: "If ever I get proof that Gomez died by or through you, I'll shoot you like a dog. Bola!"

The Indian moved to his side. Heneky said a few words to him. Bola looked aloft. Mollendo hung immediately over the pool; if he fell he must plunge into it again. The Indian sprang up, caught hold of one of his boots, and tried to shift his position laterally.

"Take care!" cried Pedro. Bola was dangling dangerously.

"We must help," said Derrick. "Hold me so that I don't topple in: Bola can stand on my shoulders."

And then was seen the strange sight of the big man being slid along the roof as though he had been on the floor.

"His centre of gravity isn't over the pool now," said Derrick presently. "Must he remain till he is dry?"

"Take a hold of his two legs," said Heneky. "Tug hard."

Bola and Pedro between them succeeded in forcing the legs from the roof; then, with their own feet on the ground, they were able to exert a stronger pull. Derrick and Heneky lent a hand, and the man was by degrees peeled off, as Heneky put it. Even when set on his feet he was remarkably buoyant, and had some difficulty in keeping his balance, though the four kept a hold on him.

"Run him out into the sunlight," said Derrick. Mollendo was wholly incapable of effort, and the others carried, or rather piloted, him into the open. There he stood among them, an image of astonishment, while they held him, watching with grave interest. The captain of gendarmes looked on with an expression that varied between sympathy, suspicion, and a wondering curiosity.

In a few seconds the sun's heat had dried enough of Mollendo's person to break the film of liquid and make further detention unnecessary. He seemed surprised when he was able to sit down.

"You are a witness, Captain de Silva," he said huskily.

"Yes; but of what?" said the captain.

"Of what! Was it not plain?"

"Yes; but the cause, the means—"

"Never mind the means," said Heneky bluntly.

"Attend, Señor Capitan. I charge Miguel Mollendo on his own confession with the theft of gold that was the joint property of my friend José Gomez and myself. I hand him over to your custody, and make you responsible for conveying him to La Paz. In due time I will follow and prosecute him in form."

The captain looked round the group in the manner of a man who feels insecure and is anxious to get away. But he pulled himself together, tugged at his moustache and became the semblance of an official.

"Señor, there seems need for explanation," he said stiffly. "I came here, under instruction, to escort Señor Mollendo on his journey, undertaken for the purpose of occupying a duly registered claim."

"Ah yes; my friends here hinted at something of the sort. But I understand they informed Mollendo that this ground is already registered."

"I fear they are mistaken," said the captain with a shrug. "Señor Mollendo has already exhibited the certificate issued to him a week ago by the Office of Mines."

"I daresay he has. Mollendo, let me see it."

Mollendo produced, shakily, reluctantly, the sodden document and map. Heneky glanced at them.

"Yes, they are quite in order. The certificate was granted to Señor Mollendo. I am not surprised. He also, no doubt, made the map. Yes; the cave is marked; it appears that he has been here before. He spoke to you, on the way, of the-the bathing pool?"

There was no reply. Mollendo and the captain both glanced towards the cave; Mollendo shuddered.

"Neither my friends nor myself would deprive Mollendo of property to which he has a prior claim," Heneky went on. "But there must be a misunderstanding; it must be cleared up-at La Paz. I hold you responsible for the safe custody of this confessed criminal." He paused a moment, then added quietly: "And to make quite sure, I will go with you myself."

The boys started.

"You won't leave us, Pat?" said Derrick.

"Sure and I'm sorry to desert you," said Heneky, "but I cannot help it. Bola tells me this spalpeen is the man he saw with Juan. Now that I have caught him I owe it to my old friend Gomez to clear up a matter that's been weighing on me for seven years. There's not much justice to be had among these dagos, but it's up to me to get what is to be got. And there's this bogus claim; some villainy at the bottom of it; that must be cleared up too."

"But the machine!"

"I can't set the machine, though 'tis like my child, against my friend. Besides, 'tis nearly finished. You've done the plans; you can keep the men working to them. And the sooner you get it tested the better now that our claim to the cave is challenged. If we are to fight 'tis as well to know what we are fighting for."

"Is it safe for you to go with these fellows?"

"I'm not afraid of their tricks," said Heneky with a smile. "And believe you me, I'll be back as soon as I can."

Seeing that Heneky's mind was made up the boys made no further effort to dissuade him. They were amused as they watched the departure of the party: the captain and Mollendo, aggrieved and sullen, on their mules, Heneky and Bola on foot bringing up the rear like drovers shepherding cattle that had strayed. But their hearts misgave them when their friend had passed out of sight, and they turned rather disconsolately to the interrupted task of pegging out their claim.

CHAPTER THE ELEVENTH - THE TRIAL FLIGHT

BEFORE they left the neighbourhood of the cave the boys got their Indians to drive into the ground a number of pegs to mark the boundaries of their claim. They also parcelled up all the crystals they had obtained by evaporation, a quantity large enough, they thought, to last a long time when dissolved again.

On their return to the hacienda Señora Alvarez was much perturbed at the news they brought.

"There is certainly some trickery behind it all," she said. "It would be too strange a coincidence if this man Mollendo had discovered the cave independently. And you tell me that he had the air of a stranger in approaching the cave?"

"Yes: I am sure he had never seen it before," said Pedro. "Is it possible that Manuel Manuel was the messenger who had conveyed the papers to La Paz.

"I begin to fear that I can trust nobody," said his mother distressfully. "Manuel seemed to be a faithful servant."

"Don't worry, Aunt," said Derrick. "You can trust Heneky at any rate, and I daresay he will get to the bottom of the mystery."

He spoke more confidently than he felt, being still oppressed with the feeling of uneasiness which had seized him on Heneky's departure. But it was no good looking on the black side of things; there was work to be done in finishing the machine, and he and Pedro made up their minds to hurry on with it, and have it ready against Heneky's return.

One of their last difficulties was the preparation of slightly rounded glass to fit the windows in the hull. Their first experiment in melting the flat sheets given them by the señora, and running it into moulds, resulted in failure; but at their next trial they succeeded in moulding four passable curved sheets of very thick glass, not of the finest quality, but clear enough to serve their purpose. The glass was fitted into frames in the front and on each side of the pilot's seat, and the edges were tightly packed with india-rubber, thus reducing the danger of shock to the glass and rendering the frames air-tight.

A barometer was necessary for the calculation of heights. This presented a difficulty. The ordinary aneroid barometer was useless, and a column barometer that hung on the wall of the porch could not be placed in such a way as to be at once sensitive to the outside air and yet readable inside the cabin. After a good deal of consideration they decided to make a barometer especially for their purpose. They carried a tube improvised from a length of boiler-gauge glass through the bulkhead, the scale being marked on the inside. The surface of the mercury, being aft of the bulkhead, was exposed to the outer air. Neither Pedro nor Derrick expected any nice degree of accuracy from so rough a contrivance, but as their aim was practical and not scientific they hoped it would suffice.

While these minor details were being completed and the finishing touches were being put to the machine, Derrick had his time fully occupied in familiarising himself with the action of the levity apparatus and the flying controls. A great deal of experiment was necessary, before the machine took the air, to find out just how sensitive she was to the action of the levity in different cells, and what her attitude would be relative to the horizontal under these conditions.

All the staging necessary for the constructional work had by now been removed, and the craft rested on her skids on the floor of the shed, where her cleanness of line and beauty of form could at last be seen in their entirety. A pair of strong timber trestles were rigged up, one on each side of the hull, and braced up to the roof of the shed, so as to be perfectly rigid under any circumstances. A pair of semi-circular discs, eighteen inches in diameter, were bolted on to the wings, one on either side, near the roots, to form roller bearings. The machine was then raised and mounted on the trestles so that the rollers rested in guides, allowing the machine to swing in a fore and aft direction about the front wing spar, and take up approximately the same attitude as it would if the same forces were acting upon it in the air; the upper guides which were necessary to prevent a premature flight through the roof, allowed about an inch of play above the rollers.

"Whatever happens," remarked Derrick, climbing into the cabin, "there's not much chance of our hurting the machine, or anything else, if we only fly an inch high for the first time!"

Pedro's only duty, at this time, was to work the hand pumps which maintained the necessary pressure to drive the water or air, as required, into the lifting cells. When the pressure gauges recorded about 151bs. per square inch, Derrick, sitting in the pilot's seat, gingerly opened the throttle, as he called it, admitting the water to the middle or number 3 cell. They heard the balls clicking against the roof of the cell, and in a few seconds the nose of the machine began to point upwards. Number 2 cell, the next in front, was then brought gradually into action, and the nose continued to rise more and more steeply until it pointed up at an angle of about 30 degrees. Both boys became tense with excitement as the crucial moment approached, for Derrick had already estimated from experiments and calculations that it would require the force of two charged compartments to neutralise the effect of gravity. The experiment, although not spectacular, and carried out in the secrecy of the shed, was, they fully realised, the turning-point in their labours.

As the second cell became fully charged, they felt a slight lurch, and realised, with a thrill, that their labours were crowned with success. The machine, with her nose pointing skywards, seemed to their excited minds to be as anxious to cleave the air as they were, like a hound straining at the leash. Gradually closing number 2 throttle, at the same time opening up number 4, and opening the air inlet to dry the balls in number 2 by means of one of the foot pedals, Derrick brought the machine back to a more normal attitude, and then shut off the levity altogether; the cabin was getting hot and stuffy, as it had not been conveniently possible to provide for ventilation while on the ground.

Having taken the first step, it was difficult for the boys to sit in the machine, or even go into the shed without wanting to flyaway then and there. However: as undue haste might bring disaster, they continued, for the next few days, their tests on the levity apparatus, and reduced the result of their experiments to cut-and-dried facts. The effect on the attitude of the machine of any combination of cells was tried and simultaneously, with the help of the foreman, the only man among the mine-workers who had been let into the secret, they measured the actual lift of the machine by means of steelyards rigged up on the trestles. The minimum time required for each operation was also a vital factor; they found that to neutralise gravity completely so that the machine "had no weight" occupied about four seconds, and to break the film of levity solution on all the balls in one cell, thereby destroying the lift, took about two and a half seconds. Derrick also practised assiduously such operations as changing trim, from climbing to diving attitude, and the many intermediate positions that might arise. The fact that it might be necessary to effect this manoeuvre without altering the magnitude of the lifting force made this a matter of skilful manipulation of the throttle lever and pedals.

It was about a week after Heneky's departure when the machine was ready for the first trial. There had been no news from the Irishman, and the edge of their enthusiasm was a little dulled by his absence; on the other hand they found a certain pleasure in the prospect of showing him a proved success when he did return.

On the morning when the trial was to take place every person on the estate was a-tiptoe with excitement. The household servants gathered in front of the house; the Indian labourers and miners clustered about their huts on the hillside and the little band of skilled workers who had had part in the construction of the machine stood expectant and self-conscious by the staging on which it was propped up. Even they had only the vaguest notion of the properties of the machine they had helped to make; and the place hummed with a hubbub of conversation until the señora and the two boys were seen issuing from the house. Then a hush fell on the assemblage.

"Makes one nervous," laughed Derrick. "What a pity we couldn't do everything secretly until the machine was proved!"

"You'll be careful, won't you?" said his aunt.

"I'm a little anxious now that it has come to the point. You won't be too venturesome at first?"

"Oh no! We don't want a smash. I shouldn't like old Pat to come back and find us ruefully contemplating a heap of junk."

"I was thinking of your limbs, not of the machine. That could be made again."

"So it could be! But I shouldn't like anyone to have a hand in it but ourselves. I assure you we'll be careful; regular slow-coaches; one step at a time, like baby learning to walk. First step: to make the machine rise. What a sell it will be if she won't!"

"A regular wash-out," said Pedro.

"I think she will, though," rejoined Derrick. "Second step: to bring her down without a bump that'll set our bones rattling. Third step: to test the—"

"Don't go on," pleaded the señora. "You can tell me all about it by and by. I'd rather not hear any more details yet."

"On the principle that 'ignorance is bliss.' Very well, Aunt; I don't suppose we shall get to the third step to-day."

Leaving the lady to watch from a little distance, the boys went down to the machine and waved back the crowd of onlookers to clear the little open space. Two persons only remained, the foreman of the workers and one of the men. Derrick and Pedro then entered the hull by a low door forward of the bulkhead. The tanks had already been filled with the levity solution, as they called it. They examined the various appliances and then both got to work on the pumps. When they had raised the necessary pressure in the air and water tanks, Derrick took his place in the pilot's seat, and tried the flying controls, while the foreman signalled to him, through the cabin window, that they were working satisfactorily. He then pushed open the throttle of the central levity compartment, and when the rattle of the rising balls had ceased, he partly opened number 2 throttle, this time more carefully, and made a sign through the window to the foreman, whom he had previously instructed what to do. The man stooped down and grasped the main skid on one side, his companion doing likewise on the other. A gasp of amazement broke from the spectators when they saw the two men lift with the greatest ease the cumbrous machine, weighing at least three tons, from the staging. At another sign from Derrick they let it gently down.

A buzz of excited chatter arose from the throng. How had the two señors inside the strange fish-like machine managed to endow the two men outside with such amazing strength? Señora Alvarez, whose cheeks had gone a little pale, relaxed the rigidity of her posture, and waved her handkerchief.

"It's all right, old man," said Derrick exultantly.

"She'll go up when I've flooded another compartment or two. Look out!"

He then opened the throttle to its fullest extent, and the men outside, still holding the skids, allowed the machine to rise until it was above their heads, and it required all their weight to keep it down. At another sign from Derrick they released their hold, and the machine immediately commenced to soar slowly upwards, gathering speed as it did so. Derrick did not propose, at this early stage, to apply the full force of the levity, as this would only have had the effect of increasing the speed, and of making the machine more difficult to handle. His aim was, therefore, to keep just a sufficient margin of lift to enable him to rise slowly and accustom himself to the feel of the machine, and to the sensation, completely new to him, of being up in the air. As the ground dropped away beneath them, the diminutive figures with upturned faces, watching them from the mine-workings, reminded them of the appearance of Ludgate Hill from the dome of St. Paul's. When they had risen about fifteen hundred feet, Derrick shut off the levity, with the intention of testing the elevators, and as he admitted the air blast to the dry balls, they commenced to dive rapidly earthwards. Pulling the control column towards him, he succeeded, to some extent, in checking their progress, but the earth still seemed to be rushing up towards them as they descended into the valley again. Hurriedly he charged numbers 2 and 3 cells once more, and the machine slowly flattened out, but only just in time to clear a wood of tall pine trees by inches.

"Whew! That was as close a shave as I want," said Derrick, mopping his brow, as they climbed skywards again. "I shall have to practise getting a better adjustment than that if we're going to come down with whole skins."

"Rome wasn't built in a day," said Pedro.

"No, but we might smash in a minute. The difficulty is to get just the right amount of levity to make you rise or sink, according as you desire, and then to change your altitude without altering your lift."

They had flown some miles up the valley now, and, as he swung the wheel round, the machine banked over and came round in a wide circle, into the opposite direction.

For the next twenty minutes, while Pedro applied himself to the pumps, whenever necessary, and divided the rest of his time between occasional glances at the barometer and pressure gauges and watching the earth slip by beneath them, Derrick devoted all his attention to mastering, completely, the action of the levity and elevator controls with different combinations of the cells in action, and with the machine sometimes heavy and sometimes light. He also brought the rudder into play to try its effect under different conditions, and when his confidence was more fully restored, the difficult task of landing had to be faced.

To practise, Derrick selected a tall tree, that stood by itself in the valley, as a landing-mark, and reduced the lift until the machine was sinking almost imperceptibly; then, putting the nose down by the elevators, he approached the tree in a slow glide at about fifteen miles an hour, steering slightly to the right of it. Pulling the stick back as he neared his objective, he flattened out too soon, and passed about 20 ft. above the top. The next attempt brought him too low, but after repeated attempts he was able to finish, as near as he and Pedro could judge, just on a level with the topmost branches. Thus encouraged he prepared to land in earnest, and glided down towards their jumping-off place. Turning across the valley, to avoid the shed as they neared the ground, a sudden gust of wind caught the machine sideways, when too low down to recover, and one skid hit the ground heavily, and the end broke off, causing the machine to bounce badly before finally coming to rest. Both boys were thrown violently out of their seats, but, with the exception of a few small cuts and bruises, escaped unhurt.

They got out and quickly inspected the machine, round which the mine-workers were now crowding with renewed interest and wonder. The broken skid could easily be repaired, and they made a close examination to assure themselves that no further damage had occurred. After Derrick had given instructions to the foreman concerning the skid, the boys rejoined the señora.

"Well, Aunt," said Derrick, smiling, "are you ready to take a trip?"

"Good gracious, no!" exclaimed the lady. "My heart was in my mouth when I saw the thing rocking. And you went much too high."

"My dear Aunt, we have only hopped at present. Wait till you see us soar. We have proved that it will rise; that's the great thing. To control it will come with practice."

"I don't see that it's much good after all," said the señora. "What is the use of just going up and down? The machine would be much more useful if it would fly horizontally."

"Well, it will be able to do something equivalent to that as soon as we have learnt how to manage it. When we use all the compartments it will go up with tremendous speed. We can alter the inclination of flight by means of the elevator, and when we get high enough we can swoop down in a long glide and cover miles and miles of country. You'll see! But now I've a most powerful thirst. A pint of your lemonade would be grateful and comforting, Aunt. Come along."

He linked his arm with the lady's, and they returned to the house.

The experiments thus satisfactorily begun were continued for several days, and Derrick became more and more adept as a pilot as he acquired more confidence in himself and in the machine. He was careful to see that the levity force was wholly shut off, so to speak, before either he or Pedro left the machine, lest it should start on a voyage uncontrolled. Not that it would rise very far, for the difference of their weight represented only a slight degree of upward pressure, and they found early in their trials that, either from evaporation of the liquid on the balls, or from some other cause affecting the continuity of the film, the lifting force gradually ceased unless the charge of the solution was steadily renewed. Without the use of the air-pump they heard the balls dropping at intervals to the bottom of the compartments that were not kept charged.

It was not until they had made several ascents to the height of a few hundred feet and come safely down, that the boys felt sufficiently at home in the machine to attempt a real flight. So far they had risen and descended with equal slowness, and had not really put the machine through her paces. Derrick considered that the time was now ripe for testing the machine to its full capacity.

Before starting on this crucial test they made a thorough overhaul of the machine, and carefully tested every part to see that it was in good order.

"Everything works smoothly," said Pedro. "There's no sticking. The question is whether they'll stand the strain when we get up in the air."

"We'll have to risk that," replied Derrick. "And I've made up my mind to go really high this time-if you're ready to chance it."

"What do you mean by 'really high'?"

"Twenty thousand feet or so."

"I say, you haven't told Mother?"

"No: I didn't want to scare her. But I look at it like this. When we're once off the ground it makes no difference how high we go, so far as our personal safety is concerned. A hundred feet up, or ten thousand, it's all one if we fall: we shouldn't take any further interest in things."

"That's true. Well, I'm game."

"Good man. Are you ready?"

They had taken their customary places. The door was shut.

"Go!" said Pedro.

Derrick charged the four compartments. The machine rose steeply. In a few seconds Pedro reported that the height was a thousand feet. Through the windows the countryside appeared to be contracting; the rate of ascent accelerated, but the motion was so smooth that he was only aware of the increased speed by the quicker diminution of the features of the landscape and the evidence of the barometer.

"Two thousand feet," Pedro called, and it seemed but an instant before he announced three thousand feet. The machine was already rising with a speed much greater than that of an express train. The crowd beneath had disappeared from sight. And then a vast panorama opened out before the eyes of the aeronauts. They had risen above the hills surrounding the valley; peak after peak, range after range of the Andes came into view. The prospect was so magnificent that for a while they forgot both themselves and the machine, and Derrick was only recalled to his actual situation by a sudden consciousness of cold, and the hissing of the air as it rushed through the inlet pipe.

"'What's the reading?" he called sharply. "Twenty thousand feet," replied Pedro.

"Quick! Shut the outlet."

Pedro sprang to the forepart of the machine and closed the outlet.

"Now the inlet."

In three seconds it was done, and only just in time: the boys were already feeling giddy in the rarefied atmosphere.

Shutting off the levity from two compartments, Derrick pressed down the pedals admitting the air blast. But the machine continued to rise.

"Twenty-three thousand," Pedro called: then "Twenty-four thousand," and, after a rather longer interval, "Twenty-five thousand." They were above all but the highest of the peaks; the whole globe seemed to be slipping away from them: they were adventuring into limitless space.

Derrick opened the air inlets to the other compartments, Pedro watching the barometer anxiously; he said afterwards that he was shaking with fright, for the machine still rose. Were they at the mercy of an uncontrollable force? But in a few seconds he observed with relief that the ascent was checked; the mercury indicated 24,000 feet, then 23,000. The machine was falling. They soon realised that the rate of fall was less rapid than that of the rise. Yet it seemed barely an instant before they were down to 10,000 feet. The air was already stuffy, owing, no doubt, to the loss of pressure during the ascent.

"Open the inlet," Derrick called, at the same time pumping the liquid into one of the compartments he had dried.

The rate of fall was checked; Pedro soon reported that it was reduced to a hundred feet a second. But even this Derrick felt was too fast; in little more than a minute they would reach the ground. Then for the first time he brought the elevators into play. He found the control column difficult to turn, and had a momentary fear lest the elevators should break off under the immense pressure of the air. But he was relieved when he found that a very slight movement had an appreciable effect. Exerting the full strength of both hands and bracing his feet against the footrests he pulled the column still further towards him; there was a sudden sharp report, and he was jerked backward in his seat as the strain on his hands was relaxed; something had snapped.

Derrick realised that he had only a few seconds to spare. He instantly flooded two compartments; but the barometer recorded a further drop of two thousand feet before the falling momentum was neutralised.

"Only a thousand feet above ground," said Pedro, his teeth chattering. "Ah! She is rising. Fifteen hundred now. Don't go up any higher."

But Derrick needed a little time to collect himself before attempting to land. The breaking of some part of the elevator-control compelled him to rely wholly on the levity.

"Where are we?" he asked.

In the excitement and agitation of the last few minutes they had neglected to keep watch upon the direction in which they were travelling. They had started towards the south-east, but had no means of telling how far they had flown in that direction, and it was clear from the position of the sun that the machine was now pointing almost due north.

"You're a nice observer!" said Derrick chaffingly. "It's the pilot's job to keep the course," retorted Pedro.

"Well, we must bring a compass next time."

"Of there is a next time."

"Of course there will be. But I don't recognise the country about here. I must try a circling movement. Keep a good look-out."

Rising slightly, and gently operating the rudder control, he brought the machine round in a wide spiral. To the north and west the mountains gleamed and glowed in the sun's rays; eastward extended a vast expanse of forest and champaign, through which innumerable streams meandered, like silver serpents stretched upon grass. But the configuration of the mountains was unfamiliar to them; they failed to pick up any landmarks; there was no sign of human settlements; and after circling round for some minutes at varying heights Derrick realised that aerial flight presented problems still to be solved.

All at once Pedro called out that he saw some native huts in the midst of a wood.

"We had better land and ask our whereabouts," said Derrick. "Luckily you can speak the lingo."

"It may be risky," said Pedro. "Some of these Indians are very wild."

"The risk is that the machine will scare them away and they won't come within speaking distance. But I see nothing for it except to try; we might go on wheeling about like this for hours."

Steering the machine until it was vertically above the clustered huts, Derrick brought it down by easy stages to within about two hundred feet of the ground. They saw among the huts a number of Indians, half-naked or partly clothed in bright-coloured garments, moving hither and thither with signs of manifest excitement.

Suddenly they were startled by a slight thud, followed by the unmistakable crack of a shot. Another and yet another shot followed. Derrick instantly jammed down the piston of the levity pump, and the machine soared into the air.

"So much for scaring them," said Pedro.

"And so much for our chance of asking our way. We daren't risk having our hull riddled. All we can do is to chance our luck. I think we should make for the north-west. Clouds are beginning to settle on the mountains, and if they spread and we find ourselves befogged, we shall have to come down, wherever we are, and perhaps have to spend the night in the jungle."

"With no Roving Pat to help us! Get a move on, old man."

The elevators being out of action Derrick's only course was to utilise the natural tendency of the machine to incline itself up or down, according as the levity or gravity was in action, and he proceeded across country by a series of rises and falls between 3,000 and 10,000 feet. Even then he could not tell what effect the wind might have, blowing against him. Thus to an observer on the ground-and it was afterwards discovered that there were many observers-it would have appeared that some strange fish-like object was cavorting about in the sky in a series of steep loops, as though on an aerial switchback.

Both the boys kept a very keen look-out. The valley in which the Alvarez hacienda lay was close against the foothills, and Derrick had expected little difficulty in distinguishing it. But he found that at altitudes greater than a mile it was almost impossible to be sure of the nature of the country below. Its physical features seemed to be squeezed together, and its various shades of colour to coalesce into a uniform purplish grey. He guessed that only an experienced airman would be able to analyse the panorama spread beneath him.

Steering so as to follow as closely as possible the irregular outline of the foothills, Derrick had continued the switchback movement of the machine for a considerable time before Pedro at last sang out that he thought he had spotted the hacienda and the mine some distance away to the west. A sharp rise and the use of the rudder brought the machine vertically over the place. There was no longer any doubt. The house, its gardens, even the miners' huts on the hillside, could be clearly distinguished, and the multitude of moving specks must be the crowd of spectators.

By the careful manipulation of his throttles Derrick managed to bring the machine gently down within a couple of hundred yards of its starting-place. The spectators had flocked to anticipate its landing, and when it settled upon the ground, and the two boys opened the door, the air rang with joyous shouts:

"I am so thankful." said Señora Alvarez, embracing her son and nephew in turn. "It was dreadful to watch your machine getting smaller and smaller, and at last vanish altogether. I don't think I like It.

"But, my dear Aunt," said Derrick, "in a little while it will be just as common a sight as a liner disappearing on the horizon. We've had a topping time. By the way what is the time? We seem to have been away hours." He took out his watch, stared, laughed. "I say Peter how long do you think that stunt took us?"

"Three or four hours, I suppose," returned Pedro, looking at his watch in turn. "Why, it's five to four."

"Yes; we've been exactly fifty-five minutes."

"You don't mean to say you didn't know?" said the señora incredulously.

"Didn't even think about it; far too busy to bother. But we must have flown a good few hundred miles. Let's go indoors, and we'll relate our adventures in space."

CHAPTER THE TWELFTH - WINGED

"I HOPE you won't try any more experiments until Pat is back," said the señora when the story was concluded. "What with a broken plane and Indians' bullets—"

"Come now, madre," Pedro interrupted, "Pat couldn't have saved us from either. We'd like his company, of course. How long has he been away now?"

"Just over a week. He may come any day-but I shouldn't be surprised if he were away months. The wheels of the law sometimes move very slowly in La Paz."

"Well, we really can't wait for him," said Derrick.

"To-day's flight was a great success; you can't deny that; but we haven't learnt nearly enough about our machine yet. By the way, we ought to give it a name."

"Bird-beast-or fish?" said Pedro.

"I meant a general name, like airship or aeroplane. It's not exactly either. What about levitator?"

"Horrible!" said the lady.

"Air-taxi," suggested Pedro.

"Not bad," said Derrick. "Which reminds me that we ought to have a clock to hang beside the barometer: one with a good second hand, so that we can measure the rate of ascent and descent."

"I can provide that," said his aunt. "But the name!"

"Let me see," said Derrick, affecting a solemn air.

"Gravity, levity; 'from grave to gay': gaiety, frivolity: flighty people-I have it: call her the Gadabout; the name fits her well after her antics to-day."

"That's a wonderful flight of fancy, Derrick," said the señora, laughing. "If that's your vein, why not call it the Gadfly?"

"Splendid! Begad, she can fly! The Gadfly she shall be."

"But I hope she won't sting," said Pedro.

"On the contrary, I hope she'll sting pretty hard if she's molested," said Derrick. "Who knows what her uses may be? Well now, we had better go and see exactly what has gone wrong with her tail. Nothing very serious, probably."

Inspection showed that the joint between the elevators and the control-rod had snapped. The foreman undertook to repair it at once, and next morning the Gadfly was ready for another flight.

Not yet having used the levity compartments simultaneously, Derrick had not put the machine to a thorough test for speed. This was to be the object of the day's flight. Before starting, the boys thoroughly overhauled the machine, installed a clock, and a small Primus stove on which to prepare hot drinks if they should remain any length of time in the higher regions. They found that there had been some wastage of the liquid, and refilled the tanks."

"And now we will try her paces," said Derrick, as he strapped himself into the pilot's seat.

He started slowly. From the accident to the control and sundry creakings and groanings of the hull and framework he had realised there was a danger of bringing too sudden a strain upon the structure. The power exerted by the levity force, if applied too quickly and in large quantity, was so enormous that there was grave risk of straining the hull and causing leakages of air which at very high altitudes might be fatal. As the first day's experience had shown, there was equal danger in checking the machine too suddenly on a downward swoop.

After a few preliminary evolutions to get the "feel" of the machine, as he put it, Derrick flooded all the compartments in turn, and at the same time raised the elevators until the Gadfly was climbing rapidly at an angle of about 45 degrees. Within a minute she was rising at the rate of 500 feet a second; in another ten seconds at 600 feet. Pedro had already turned off the air-taps, in spite of which they were conscious of intense cold, and in another half-minute the barometer indicated a height of eight miles.

"Eight, did you say?" asked Derrick, astonished. "Eight it is!"

Derrick at once shut off the levity force, and a few seconds later the Gadfly began to drop, the angle of 45 degrees being still maintained by depressing the elevators. The rate of fall was soon more rapid than their rise. Within half a minute they were swooping earthward at more than 700 feet a second; a few seconds later the speed had increased to 900 feet a second. By this time Derrick thought it wise to check the rate of fall; but before his cautious employment of the water produced its full effect they touched 1,000 feet. It was not until the machine had dropped to within two miles of the ground that Derrick succeeded in flattening out by the combined action of the levity force and the elevators.

Meanwhile Pedro, by means of a small pocket compass, had taken careful note of their direction, which had been consistently southward-the direction of the cave. The hills over which they had laboriously tramped in visiting the cave were below them.

"Let's have a look at it," said Derrick when informed of this.

Two more upward and downward glides brought them above the cave, and then Derrick let the Gadfly sink gently down until she hovered about fifty feet above the ground. The place appeared to be exactly as they had last seen it. The pegs had not been interfered with; there was no sign of anyone having visited the spot.

Rising again, they resumed their flight in the same direction. A short distance southward, in a hollow of hills, they saw a small lake, no doubt the habitation of the frogs whose booming they had heard on their first night in the cave. Some few miles farther on they caught sight of a number of buildings in the centre of a clearing far to the east. Owing to the distance the buildings seemed very small, and the boys could not determine whether they were an Indian Village or an extensive hacienda. They promised themselves a visit to the place on another occasion.

Presently they swung round to the north, heading for home. Derrick put the machine through a series of evolutions, rising and falling with and without the aid of the elevator, flying straight ahead, or bringing the rudder into play and describing large spirals, diving and climbing steeply, hovering almost motionless. Every now and then Pedro glanced from the compass to the distant mountain chain, to make sure that they were keeping their course.

They were flattening out after a short dive when he noticed on their right a cluster of huts amidst trees.

"I fancy we're near the place where we were shot at yesterday," he said. "Better rise, old man."

The words were hardly out of his mouth before several shots rang out. Derrick at once opened the throttles, but he was surprised to find that the machine made only a slight ascent.

"The pump sticks," said Pedro. "I can hardly move the lever. I wonder what's wrong? By George! She's sinking!"

"Not fast?" asked Derrick anxiously.

"Oh no, quite slowly, but there's no mistake about it."

"Are we near the village?"

"A mile or two beyond it, I should say."

"Thank goodness! We shall have to land and overhaul the machine. Did you hear any of the shots strike her?"

"No; but the balls were clicking at the time."

"Well, look out. I'm afraid we may make a bad landing."

The rate of descent was barely more than walking pace, but it was clear that the inflow of water into the compartments was barely sufficient to overcome the force of gravity. They were now passing over a small stretch of scrub bordered on one side by a stream, on the other by woods.

"We're not much more than fifty feet above ground," said Pedro presently. "In a few seconds we'll strike."

At that moment he noticed that the machine was slightly down by the stern, and realised that if the tail struck the ground first the rear skid, in spite of its rubber shock-absorber, might crumple up. Acting on instinct he darted forward. His weight caused the nose to tilt downwards, only just in time, for a second or two later there was a sharp shock accompanied by a grinding noise. Derrick, strapped in his seat, felt only an unpleasant jar, but Pedro was flung violently towards the side of the machine, and clutching one of the struts of the framework to save himself, wrenched his left shoulder.

"The Gadfly can sting," he said. They climbed out.

"We've escaped the stream by a few yards," said Derrick, "otherwise we should have seen how she behaves as a waterplane. Look here, one of the skids is absolutely smashed."

"That doesn't matter much: the question is, why wouldn't the confounded thing rise?"

"There must be something wrong with the pump. I'll see."

He got into the machine again, and commenced an examination of the pump and its attachments. Meanwhile Pedro inspected the exterior of the hull.

"Here's a small hole," he called, after a minute or two.

"Whereabouts?"

"Where I am tapping."

Derrick stooped down in the interior, and guided by Pedro's taps soon discovered the hole.

"Here's a bullet too" he cried. "It's just below the tank. I'll find out in a jiffy what damage it has done."

Lying flat, he thrust his arm into the space between the tank and the curved side of the hull and groped about.

"I've got it," he said presently. Pedro had come in. "The bullet struck the pipe between the pump and the tank and flattened it. No wonder I couldn't force any water through. But it might be worse. If the bullet had penetrated the tank itself we'd have lost all our solution, and come down a frightful crash."

"What can be done?"

"We shall have to disconnect the pipe and press out the dent. There's nothing else for it. Memento: another time we must come provided with some spare lengths of tubing for emergencies: rubber would do as a makeshift."

"You'll have to plug up the tank."

"Of course and a ticklish job, difficult to get at. But it's got to be done. Hand me the spanner."

Moving towards their tool-box in the after-part of the hull, Pedro happened to glance through one of the windows.

"Goodness, Derrick!" he exclaimed. "There's an Indian behind a tree not a hundred yards away, covering us with a rifle."

"Confound him!" growled Derrick. "What asses we were not to bring our rifles! Perhaps he won't fire unless we show ourselves. D'you think he saw us when we were outside?"

"Can't say. He certainly couldn't have seen us inside, and he may be simply puzzled as to what this strange creature is. But heavens! There are more of them among the trees."

"Armed?"

"I don't know. Yes: I see another rifle, but only one. There are at least a dozen men."

"Don't let 'em see you through the window. I must hurry on with this job."

A moment later there was a crack, followed instantaneously by the smack of a bullet against the hull. Another shot was fired.

"It's no good," said Derrick, getting up. "They'll riddle the machine like a sieve if they keep it up. We must save the tank."

"You mean we must show ourselves?"

"Yes. When they see us perhaps they won't be afraid of the machine."

They opened the door and, holding up empty hands, stepped on to the ground. There was an outburst of chatter from the wood, and about a score of half-naked Indians emerged, grouped about the man whom Pedro had first noticed.

[Go to illustration for this scene]

"We are friends," Pedro called, in a patois of Spanish Indian.

The chief advanced to within a dozen paces. His features were stern. He said a few words in the same dialect.

"He says we are prisoners," Pedro translated, and proceeded to reply to the Indian, who listened to him gravely, then spoke again.

"It's no go," said Pedro. "I told him I was a Bolivian, and the Government would punish him for molesting us. He replied in effect that he doesn't care a straw for the Government. This country is his country; he has never been interfered with; and he regards our machine as some magical connivance for destroying his hunting. It's no good saying any more at present; we may talk him over by and by. All we can do now is to look pleasant."

The Indians had gradually drawn nearer. Now, at a word from their chief, they sprang forward quickly and surrounded the boys. A quarter of an hour later the aeronauts were marched through the little village amid a silent throng of onlookers, and thrust into an empty hut somewhat larger than the rest.

"They're not going to tie us up, thank goodness!" said Derrick.

"But you're mistaken if you think we'll be able to get away," said Pedro. "They'll watch us night and day; and I'm not keen to get a bullet in my back."

"What will they do with us, then?"

"Who knows? We're lucky to be alive at all. Some of the most savage tribes would have cut us up by this time. I expect they'll call a council about us, and I hope we'll get a chance to persuade them that we're harmless. We shall see."

CHAPTER THE THIRTEENTH - THE RED MAN'S MERCY

THE hut in which the boys had been placed was open on one side; their hands had been bound behind them, and they were guarded by two armed Indians standing at the entrance. By moving a little they had a full View of the Gadfly, and they were soon rather perturbed about the fate of that unfortunate vessel.

It was surrounded by a flock of the villagers, chiefly women and children, who kept at first a respectful distance from it, and, to judge by their gesticulations, were engaged in an excited discussion about its nature. Presently one of the Indian boys, becoming venturesome, darted forward, touched one of the fin-planes, and scampered back. Emboldened by his action, the crowd by degrees drew nearer to the object of their curiosity, walked round it, stroked its smooth sides, and gave it playful pokes, as a child will poke a kitten. At last one, still bolder than the rest, put his head in at the open door, holding on to the sides, and after taking stuck of the interior, clambered inside. In a few moments he returned, and apparently explained to the others that no danger was to be feared, for the crowd began to pass in one by one, like Noah's family going into the Ark.

"I hope to goodness they won't do any damage," said Derrick. "I'm surprised they're not afraid of it."

"I daresay they were until they saw us," said Pedro. "But if they took it for some strange sky monster, they were undeceived when we came out of it. Still, I don't suppose they will do more than look round, at first, and if we can persuade the chief that we are harmless we may get away before their inquisitiveness makes them too bold."

"These Indians are a finer-looking set than any I have seen before. Some of them are quite handsome."

"I fancy they're one of the tribes that have managed to keep their independence. There are several on the borders of Brazil and Bolivia that neither government has been able to subdue."

"How do they get firearms?'

"By trading in rubber. It's a pity we have nothing to trade with."

"You must try your powers of persuasion. And I hope they won't keep us long in suspense."

"You see all their huts are closed except this one: that's a bad sign. The Indians never close their huts if they are friendly disposed. There's something going forward. Look at them flocking to that long shed at the end of the village."

Headed by the chief, the armed men were marching into the shed, followed by a rabble of the unarmed. Presently there came a sound as of a gong being struck, and the guards signified that their prisoners were to accompany them. The boys were escorted through the village and led into the shed. At the farther end, on a raised platform of logs, sat the chief among some of his lieutenants. The greater part of the company were seated on logs set along the walls, and the open space in the centre was patrolled by men armed with rifles, who paced up and down like policemen keeping order.

The boys were marched to the foot of the platform.

A deep silence fell on the assembly, and for some minutes the chief bent a stony stare upon the prisoners, his features expressionless as a mask. Then, in sharp guttural accents, he began to speak.

"What brought the white men into the red man's country?"

"You saw, O Chief," replied Pedro amiably.

"We came in that air-fish which you see yonder. But we had no wish to come into the red man's country. The air-fish was tired, and would not carry us any longer."

At this answer the chief held a low-toned consultation with his men.

"The air-fish is white man's magic," he said presently. "Why, then, did it not flyaway?"

It would very soon have flown away if you had not fired at it; but one of your shots injured its fin and we ask your leave to mend it."

"Why do you fly in your air-fish over the red man's country?"

"To get quickly from place to place. In the air there are no forests to block the way, no rivers to cross. We save much time."

"And the white men see many things, even as a bird sees them. They see where the red man's village is, in the bosom of the forest, and where the rubber trees grow, and they will bring soldiers and steal the red man's land, and he will no longer be a free man."

"That is not the truth," said Pedro earnestly.

"We are not spies. We do not wish to learn the red man's secrets, or to bring soldiers to destroy his peace and steal his land. If you permit us, we will very soon rise up once more into the air, and you shall see us no more."

Another consultation ensued. Again the chief put his questions, repeating them time after time in varying forms, as if to entrap Pedro into giving different answers. The interrogatory went on for nearly two hours, until Pedro was thoroughly weary of saying the same thing over and over again. The stolid features of the Indians gave no sign of the nature of their thoughts. They remained immovably grave.

At last the chief, with a movement of the hand, signified that the prisoners were to be taken to the end of the shed, while the council arrived at their decision. After a long consultation he rose.

"Without doubt the white men are spies," he said.

They do not trade. They employ magic to bring them into strange lands. They deserve to suffer death.

But the red man will show mercy. He will keep the magic air-fish; it is not fit that so dangerous a creature should carry enemies who would pry into the red man's secrets. But the white men shall be allowed to depart; if they return, death shall be their lot."

"It's no good protesting," said Pedro to Derrick.

"They have evidently made up their minds. We are lucky to get off at all."

"But how in the world shall we find our way back?" said Derrick, aghast. "Ask the chief if he'll let us have an escort."

"The white men shall see," replied the chief enigmatically to Pedro's request.

A procession was formed. The prisoners were marched back through the village to the brink of the stream. The crowd had deserted the Gadfly in order to witness the strangers' departure. An old worm-eaten dug-out canoe was loosed from its moorings. At a sign from the chief the two boys were set back to back, and held firmly in spite of their struggles while cords were lashed about their chests and ankles. Then, thus tied together, they were lifted and dropped into the bottom of the crazy vessel. It was towed out into midstream by two Indians, wading. They released it, and it began to float slowly down on the current. To cast the white men adrift was the red man's mercy.

Lying in the bottom of the canoe, the boys were overwhelmed by dire apprehension of their fate. They heard the gleeful shouts of the village children running along the bank, keeping pace with the canoe.

After a while these sounds faded away; only the low, gurgle of the stream broke the silence.

"Red man's mercy," murmured Derrick. "Can you undo the cords?"

Their hands, tied behind them, touched, but Pedro found that, strive as he might, he could not get his fingers upon the knots of the cords that bound his cousin's wrists. Derrick tried in his turn: his wrenching and twisting were in vain; the cords only cut into his flesh. He bent his head and attempted to reach with his teeth the cords that encircled his chest; but they were an inch too low. Both the boys strained at their bonds until they ached intolerably, and sweat poured down their faces. The Indians had used strong fibre, and done their work with the efficiency of experts.

"We're done for," gasped Pedro.

"Some one may see us," said Derrick.

"We might drift for days on these waterways without being seen by a soul. If we were seen, it might be by an Indian, who'd send a bullet or an arrow into us."

They lay silent. Over the sides of the canoe they saw the tops of the trees on the banks. The sun glared down upon them out of a speckless sky.

The canoe swung this way and that in the eddies of the current. At times it drifted into one bank or the other, stuck for a while in the reeds, turned broadside on to the stream, and was gradually forced out again. The boys' mouths became parched with thirst; they could not alter their position to escape the pitiless rays of the afternoon sun. Now they heard the bark of some animal in the forest, now the blowing of some creature swimming alongside; once the canoe rocked and jolted, and they guessed that it might have grazed the scaly back of an alligator. Always they drifted on.

Sickened by the heat, they by and by sank into a sort of coma, from which they were aroused by a sound that struck them chill with dread. From downstream came an ominous rumble. They were conscious of a quickening of the current. The banks were drawing together, becoming steeper. Faster and faster ran the current; the rumble increased to a roar.

"Rapids!" murmured Pedro faintly.

Despair gripped them. The stream began to pour like a mill-race through the strangled channel, bearing the canoe as lightly as a cork upon its surface. It twirled round and round; water splashed over its sides; on either hand great rocks loomed up and were left behind in a flash. Every instant the boys expected to find themselves cast into the raging torrent, the canoe swamped, or dashed to pieces upon some projecting boulder. Exhausted in body and mind, they lay inert, waiting for the end.

Then suddenly the turmoil ceased. The canoe no longer whirled, but floated quietly upon a broader, slower stream. The boys were just conscious of their escape, but what mattered it? Were it not better to drown than to lie tortured by hunger and thirst under a burning sun until slow death released them? On and on the canoe floated; deeper grew their torpor; they did not hear the light plash of paddles, nor did they see the face of an Indian who, pulling alongside in his light craft, was peering at them, timidly, in astonishment. They knew nothing of his towing them to the bank. Only when their bonds parted with a snap did they open their eyes, to see a half-naked red man bending over them, knife in hand. They would not have shrunk or murmured if he had plunged it into their bodies.

But this was a friend. He seemed to understand their plight. Without speaking a word he raised them, held to their lips a gourd filled with a sharp refreshing juice. They drank, and sighed, and drank again. The Indian grunted approval. Pedro murmured his thanks, but the Indian looked at him uncomprehending. He spoke again, in the dialect of the natives in the neighbourhood of his home. It was evident that the man did not understand him. He tried a few words of Spanish, and though there came into the Indian's eyes a look suggesting that the vocables were in some way familiar to him, he still made no answer, except to repeat "El señor, el señor." And it was by signs that he indicated his wish that the boys should leave their canoe and follow him. Rising stiffly with his assistance, they linked arms and stumbled after him as he struck into a narrow path through the jungle.

"Where is he taking us?" asked Derrick huskily.

"I don't know," replied Pedro. "But he's friendly. We shall soon see."

Unlike the usual native winding track, the path they were following cut through the forest in almost a straight line. Presently the trees ceased abruptly, and they found themselves looking upon a wide expanse gleaming with the white blossom of the coffee plant. In the distance glowed the brightly painted woodwork of a large bungalow, and near by were sheds and huts.

"El señor," said the Indian.

"Thank goodness, a white man!" exclaimed Pedro.

"The end of our troubles, old boy."

The path ran straight through the coffee plantation to the bungalow. As they drew near to it, the boys saw a man in white clothes, and a panama hat, lying back in a long cane chair on the veranda, smoking a cigar, and reading a book. Lifting his eyes, and noticing two strangers approaching with the Indian, he rose to greet them. The Indian ran ahead and spoke to him. His face expressed profound amazement, and he came quickly down the steps of the veranda.

"Gentlemen, I hear an astounding story," he said in Spanish. "You have suffered. Come in: welcome to my hacienda. There will be food and drink instantly; when you are refreshed I will ask you to tell me all about what must have been a very disagreeable adventure."

The boys dropped limply down upon the chairs which their host placed on either side of his. Servants brought fruits and refreshing drinks.

"Mine is a bachelor establishment," said he, "and I cannot offer you any delicacies; you will see at dinner-time the extent of my resources; but I can promise you at least a cup of good coffee." He glanced around his plantation with an air of pride. "All the work of a few years, gentlemen. After knocking about South America from Patagonia to Ecuador I settled down here to grow coffee. Not that I was tired of a roving life, but I lost one who had been my companion for many years in all my wanderings, and my outlook has changed. I happened to come across a small Indian settlement not far from here, and was much struck by the excellence of the coffee offered me by the chief. I purchased all this ground from him, and started to clear and plant, with some success, as you see. There are two difficult portages between my estate and uninterrupted navigation on the Amazon; but in spite of that I am doing already a good business."

The coffee-planter had evidently been talking partly to give the boys time to recover, partly out of a natural pride in his estate.

"Now, you will like to wash," he said. "My bathroom, such as it is, is at your service. By the time you return dinner will be ready, and at the table I shall be greatly interested to hear your story."

"A very decent chap," said Derrick to Pedro when they were by themselves in the bathroom.

"Well, there are decent fellows among us Bolivians, you know. But I agree; he's a specially good sort: comes from his knocking about so much, I expect."

At dinner-and for the quality of the fare no apology was needed-the planter was interested to the point of excitement in the boys' account of the machine whose breakdown had led to their unhappy plight.

"It was yours, then," he said, "that extraordinary object I saw diving and leaping in the sky. Once or twice I have seen aeroplanes-not in this country-and when my people called me to look at a strange creature in the air I expected to see either a plane or an airship flying a steady course. The undulating movement of your Gadfly filled me with astonishment, and when I took my binoculars for a nearer view I was still more amazed to find it unlike anything I had seen before, in the rapidity of its flight as well as its shape. Frankly I should not have believed you without the previous evidence of my own eyes, and my great regret is that I shall not be able to inspect your machine closely and even make a flight with you."

"You think we shall not recover it?" asked Pedro.

"I fear not. I know of the tribe that captured you: they have never given me any trouble, but they have a bad name. They keep themselves very much to themselves, and resent the approach of strangers. More than once unwary prospectors have had to flee for their lives. Nothing short of a military expedition would induce them to part with your machine. The border between Bolivia and Brazil in this district is very vague. We are here in Brazil, but I am not at all sure where the boundary line runs. Even if it were certain that these Indians are in Brazil there is not the slightest chance of the Brazilian Government taking action. Nor would the Bolivian, if they are on that side of the border."

"Of course we cannot expect Government action; in fact, we don't want it," said Pedro; "but surely the Indians might be persuaded to give up what is no good to them. Wouldn't they sell it?"

"Well, you have had experience of them: it will hardly encourage you to approach them again, I should think. Better let well alone, and build another machine."

"I'm afraid there's nothing else for it. But we have first to get safely home."

"Have no anxiety on that account. From what you tell me you are about three days' journey from your hacienda. I do not know that region, but with the aid of a large-scale map and your description I daresay I can direct you, and to-morrow I will send a small party of my Indians to escort you home. I wish I could myself have the pleasure of accompanying you, but I am leaving in a day or two on a business trip to Europe. I catch the steamer at San Antonio on Friday, and on Friday week I hope to take the liner at Para. When I return, in a couple of months or so, perhaps you will favour me with a visit in your new machine. I am very keen to examine your mechanism, which I am sure must be very ingenious."

Pedro did not rise to this hint. He had given no explanation of the levity force.

"I will not be indiscreet," said the planter, smiling. "At present it is a secret. Very well. Now tell me what you think of my coffee. There is no secret about that."

After breakfast next morning two saddled mules were brought to the steps of the veranda. Two other mules were loaded with provisions and a tent, and four Indians armed with rifles stood waiting.

"A safe journey, and au revoir," said the planter, shaking hands with the boys.

"Many thanks, señor, for your hospitality," said Pedro. May we know to whom we are so much indebted?"

"My name is Bernardo José Gomez de Carrera. It has been a great pleasure to entertain you, and when we meet again I trust it will be in pleasanter circumstances. I look forward, I assure you, to a trip in your new machine."

CHAPTER THE FOURTEENTH - A RACE AGAINST TIME

THREE days later, in the evening, the boys with their Indian escort reached the hacienda. Their approach had been unnoticed, for the mine labourers were all in their huts and the servants in their quarters at the back of the house. A light shone in the Señora Alvarez's room at the front giving on the veranda. The sound of their arrival brought the lady to the door.

"Oh, thank god!" she cried, rushing to meet them. "I have been in terrible distress. You are safe, unhurt?" She drew the boys into the rays of light.

"Not a scratch, madre," said Pedro, linking an arm with hers.

"But you have had an accident. You have come on mules. Who are those strange Indians? And where is the Gadfly?"

"We'll tell you all about it. You will put our guides up for the night? They've been travelling for three days."

"Of course." She summoned a servant, and gave him orders for the entertainment of the Indians. "I was afraid I should never see you again."

The boys noticed how pale and drawn her features were.

"I have scarcely slept since you went," she continued. "I made sure some dreadful accident had happened, and sent parties out to search for the wreck of your machine. I hate it!"

"But the Gadfly is quite inoffensive," said Pedro.

"I'm afraid we have lost her, but we'll build another and a better one when Pat comes back."

"Ah! Poor Pat! Troubles never come singly."

"What is the matter? Have you news of him?" asked Derrick.

"Terrible news! Only this afternoon Bola came back from La Paz. I was overwhelmed with anxiety as it was, and his news seemed the last stroke of misfortune. Pat is in prison."

"In prison?"

"Yes: and worse than that: he is already tried and condemned for murder."

"Good heavens!" cried Derrick. "But it cannot be true."

"Here it is in the newspaper Bola brought," said the lady, handing Pedro the ill printed sheet.

He read the paragraphs quickly, translating disjointedly to Derrick.

"Charge of murder brought by Mollendo. Indian witnesses. Seven years ago. Accused of murdering—" His eyes were racing over the print, "Gomez... partner of Señor Miguel Mollendo and the accused...prospecting expedition...Good heavens, Derrick; Pat is sentenced to be shot!"

"To be shot!"

"Yes, in a week. But it's monstrous. The whole thing is a vile plot of Mollendo's."

"It's very strange. You remember Pat accused Mollendo of murdering his partner. Mollendo denied it, but it's more likely to be true of him than of Pat. What was the partner's name?"

"Here it is: Bernardo José Gomez," said Pedro, reading from the newspaper. He looked up suddenly. "Bernardo José...Wasn't that the name of our coffee-planter?"

"Gomez de Carrera."

"There's no Carrera in the paper, but..." His eyes flashed with excitement. "The man's name is Gomez: the territorial title is often omitted. Gomez is common enough; so's José; so's Bernardo; but all three together! It must be our planter. He told us he'd been a great rover. And didn't he say he'd only settled down because he had lost his constant companion? That was Pat. Madre, the murdered man's alive!"

"What is all this?" asked the señora, who had listened in bewilderment. "I do not understand."

Pedro gave a rapid account of the events of the past few days.

"Then we can save Pat," cried the lady. "I am so thankful. The Indians can return to-morrow. There will be time for Señor Gomez to get to La Paz, and-"

An exclamation from Derrick, and a look of dismay on Pedro's face, checked her.

"It is too late," said Pedro. "Señor Gomez told us he was starting on a trip to Europe. He will have gone before his Indians get back. He expected to be at San Antonio to-morrow. They couldn't possibly catch him. This is awful! The only way to save Pat would be to produce alive the man supposed to be killed, and we are too late!"

"If only we had the Gadfly!" said Derrick. "We could fly after him, and overtake his steamer and carry him to La Paz. We must do it, Pedro. We must get the Gadfly by hook or crook."

"How on earth can we?" said Pedro dubiously.

"To begin with, we couldn't find our way to the place where she is."

"Gomez's Indians could guide us."

"And we couldn't possibly engage them. In any case they'd probably refuse to go near those savages."

"Bola! Send for Bola, Aunt. He has been all over the country with Pat, and may know this tribe. And he'd do anything for his master."

Bola was summoned. The boys' description of the situation of the Indian tribe was so vague that he could not identify it.

"Let him speak to Gomez's Indians, said Derrick. The suggestion proved to be a happy one. After Bola had talked a while with the strange Indians he declared that he could guide the señores unerringly to the secluded village.

"Then we'll start first thing in the morning," cried Derrick. "You don't object, Aunt?"

"I cannot, my dear. We must do all we can to save that poor man. I only fear that we shall not be in time. Suppose those wild Indians have destroyed your machine!"

"We won't suppose anything of the kind. Look on the bright side. We shall take two or three days to get there but if we once get the Gadfly going it will only be a matter of hours before we bring Señor Gomez to La Paz and confront him with his alleged murderer."

"In the meantime I must do my part," said the lady. "I will myself go to La Paz and see the President. I know him, and I will tell him what you have told me, and beg him to delay the execution. Even if you fail to follow Señor Gomez it should not be impossible to communicate with him at Para, and the President will surely wait a little before he permits the execution of a man who may be innocent."

Next morning the señora set off on muleback with three trustworthy servants, riding northward. At the same time Derrick and Pedro, also mounted, started eastward with Bola, who preferred to go on foot. They took with them a stock of food, a quantity of crystals obtained by evaporation, a length of tubing and some copper wire. The boys carried a revolver each, Bola a rifle. Two of the señora's servants went with them to bring back the mules. Señor Gomez's Indians had already been despatched on their homeward way, with orders to make all haste on the bare chance that they might arrive before their master had actually begun his journey.

On the morning of the third day, when Bola announced that they were approaching the Indian village, Derrick and Pedro dismounted, divided the loads between them, and sent the mules back. A few miles of dense forest separated them from their destination. Bola went ahead, following faint tracks with great caution, and never allowing the others to proceed until he had assured himself that there was no danger of their being observed. Progress was therefore very slow, and the sun was already setting when they arrived at the bank of the stream about half a mile below the village. Here the boys decided to hide in the jungle while Bola crept up the stream to reconnoitre.

They were so much accustomed this time to the discomforts of forest travel that they scarcely heeded the oppressive moist heat or the insects that buzzed and stung incessantly. Their whole thought was concentrated on what lay before them. Was their machine still intact? Had the Indians removed it from the place where it had descended? Would it be possible to make the necessary repairs without attracting the Indians' attention? These questions worried them, and they were greatly alarmed when by and by they heard faint sounds of commotion upstream. Had Bola been caught? Then they saw a slight glow, which grew by degrees to a strong glare. The noise increased; the cries of men mingled with the clang of barbaric instruments. What was happening?

"Hadn't we better go on?" said Pedro in a whisper. "Bola had been gone a long time."

"Better wait," said Derrick. "He'll look after himself."

They were silent again, watching the red glare, listening to the wild sounds. A rustle in the undergrowth near them caused them to look round, expecting to see Bola. But they caught sight of the form of some four-footed beast slinking through the vegetation and they gripped their revolvers, hoping that they would not have to betray their presence by a shot.

"He must have been gone at least an hour," said Pedro presently. "I can't stand this much longer."

"Another few minutes, then we'll go," said Derrick. "I'm beginning to fear that—"

The words died on his lips, for without the least sound announcing his approach Bola stood beside them. He brought disconcerting news. The machine still lay beside the stream, but the Indians had built a cover over it-a sort of penthouse resting on poles. A medicine man had posted himself in front of it, beside a great fire, and the men of the tribe, ranged in a half circle, had begun a ceremonial dance.

"We are dished," said Pedro. "These Indian dances go on for hours. And very likely the medicine man is permanently in charge and won't leave the machine."

"Are they all on one side of it?" asked Derrick.

Learning that it was so, he asked whether Bola could lead them to a point where they could see for themselves what was going on. Bola's reply was that the fire threw its light so far that there was great danger of their being discovered.

"We must risk it," said Derrick decisively. "At any rate they won't hear us through the din they're making."

Bola led the way a short distance along the bank of the stream, then struck into the forest, and making a wide circuit approached the scene from above. The machine was now between the boys and the fire. Looking on from their lurking-place among the trees they saw the fantastic form of the medicine man darkly silhouetted against the glow, and beyond the fire the half-naked dancers swaying and bounding to the music of reedy flutes and harsh drums. Beyond these again was a crowd of women and children, eager, excited, engrossed in the spectacle.

Immediately behind the machine all was in dense black shadow.

"The door's on this side, isn't it?" whispered Derrick. "I think so," replied Pedro.

"Then there's only one thing to be done. We'll creep up into the shadow. While you and Bola keep guard I'll climb into the machine and try to mend the pipe. They're making such a row that they may not hear me. If they do we shall all have to shoot, and perhaps startle them into running away. That will give us time."

Very cautiously they stole towards the Gadfly, keeping in the shadow. The slight sounds of their movements were smothered by the continuous clamour from beyond. Just outside the posts of the open shed that covered the machine Pedro and Bola halted, while Derrick crept on, silently opened the door and slipped within. The interior was lighted by the glare from the fire. Derrick looked around; nothing appeared to have been disturbed. He crawled to the tank, with a pair of pliers screwed off the joints of the pipe above and below the flattened portion, inserted a length of new tubing and screwed it up. His ears were strained all the time for some change in the noise without, some sign that suspicion had been aroused. His breath came and went quickly, and when he had finished his job without disturbance he was aware that his hands were trembling.

He crept to the pump and worked it gently. The flow of water was uninterrupted and the pressure rose steadily. Then it occurred to him to test the depth of the solution in the main tank. A considerable quantity had been lost, and must be replaced. Stealing back to the door he took up the old petrol tin they had carried as a filler and handed it out to Pedro. For him a sign was sufficient: he in his turn handed the tin to Bola, who slunk away into the darkness towards the stream. It seemed an hour before he returned with the tin full. Meanwhile Derrick had emptied into the tank half the contents of his packet of crystals. He poured the water upon them: there was still not enough; once more the Indian took the tin and crept with noiseless tread to the stream. Before he came back Derrick was quivering with alarm. The clamour outside ceased suddenly. Raising himself so that he could just peer over the lower edge of the window he saw that the line of dancers was motionless; the medicine man had stepped forward towards them, and was addressing them in a harsh sing-song. Then he turned about; half a dozen of the Indians seized brands from the fire, and whirling them about their heads, began with slow dancing steps to follow him to the shed. Behind them came the rest of the concourse, spreading out on either wing; it was evidently their intention to form a circle and dance round the strange monster.

Derrick sprang back to the door.

"Come in," he said to Pedro in an urgent whisper.

"Bola?" murmured Pedro as he clambered in. "We can't wait. He will look after himself."

At that moment there was a shout from the throng.

The Indians at the extreme left of the lengthened line had caught sight of Bola as he dashed towards the machine, grasping the full tin. They surged forward. Derrick sprang to his seat and opened the throttles. Pedro caught Bola by the shoulders, hauled him in, and shut the door. One after another the levity balls were heard clicking against the roof, and even as the Indians, a howling frenzied mob, waving their torches, rushed round to the shadowed side, the Gadfly rose slowly and bumped against the penthouse roof. Derrick opened more compartments. There was a harsh rending sound as the roof parted; the Gadfly shot upward; the yells of the spectators subsided to a hushed amazement.

CHAPTER THE FIFTEENTH - TOUCH AND GO

THE Gadfly soared up and up towards the stars. "A narrow squeak," said Derrick. "I'm shaking like a leaf."

"I was never in such a desperate funk in my life," said Pedro. "But what are we going to do? You can't set a course in the dark."

"No. I wish there were a moon. We shall have to come down when we are clear away, and wait till morning."

"Do you think you could pick up Gomez's hacienda? There would be lights."

"I doubt it, with Gomez away. Besides, I'm not at all sure of its direction. Does Bola know it?"

To Pedro's question Bola replied that he had never seen it, but in his conversation with the señor's Indians he had learnt that it lay about half a day's journey from the place they had just left.

"That's too vague," said Derrick. "We know it's not very far from the bank of the stream, and we might perhaps follow that in the starlight, but it winds a great deal, and I don't feel happy about steering in the dark. How high are we, by the way?"

Pedro struck a match and looked at the barometer. "Just over three miles," he said.

"That settles it. I'm frightfully tired; have had quite enough for one day; and I don't want to go diving and climbing and steering, always with the chance of going wrong. I'll let her down. Keep a look-out for a likely landing-place. It will be all right in the morning."

He brought the Gadfly down in a long glide until she hovered a few hundred yards above the ground. The stream was now out of sight; nothing was to be seen but the tops of the trees; but by a series of short ascents and dives Derrick presently arrived over a space that was clear enough for a descent. Here he brought the machine to earth.

"Now for a good sleep," he said. "I could do with a good supper first, but we've left our stores behind. We've had uncommon luck, so we mustn't grumble. And we'll be as safe here for the night as in our own hacienda."

"And to-morrow?"

"Well, I think we'll fly to Gomez's hacienda to make sure whether he has really gone, and also to get a breakfast, and then fly after him."

"Shall we catch him before he gets to Para? If we don't, there's precious little chance of bringing him back to La Paz in time to save poor old Pat."

"I'm not sure about that. Para's about 1,200 miles away as the crow flies, isn't it? The Gadfly will get there and back in a few hours."

"Well, how long have we got? Pat's to be shot the day after to-morrow. Gomez left, if he started when he said he would, five days ago. He was at San Antonio on Thursday, four days ago. The steamer usually takes about six days to reach Para. I say, there is just a chance we shall catch him before he reaches there."

"So much the better. But even if we don't, it will be all right provided the Gadfly doesn't break down again. We'll overhaul her to-morrow. Let's forget all about everything now; we all need a jolly good rest."

As soon as it was light in the morning they got out of the machine. Part of the roof of the shed was clinging to the wings, the wickerwork of which it was made being impaled as on the horns of an animal. There were several bullet holes in the hull; otherwise it had suffered no damage.

"We'll clear that rubbish off and plug the holes when we get to the hacienda," said Derrick. "And the sooner we are off the better; I'm ravenously hungry."

Rising to the height of about a mile, they were able to survey the country to a great distance. The course of the stream was easily picked out, and in a few minutes they descried Señor Gomez's bungalow with its numerous outbuildings and its extensive plantations, these latter looking like a field covered with snow. Yet a few minutes, and the Gadfly came gently down on the wide open space in front of the veranda, to be immediately surrounded by the household servants and the field workers who had flocked from all parts of the estate.

Great was the consternation of the negro major-domo when he saw, issuing from the side of the machine, the two young men who had been his master's guests a few days before.

"Is the señor gone?" asked Pedro.

"Yes," replied the man. "He sailed from San Antonio in the Capella as he had arranged. He will be sorry. This wonderful sky-carriage, señores—"

"I want you to get some of your men to clear away that wicker-work," said Pedro, pointing to the fragments on the roof. "And you'll give us some breakfast?"

"Certainly, señor; but this wonderful sky-carriage—"

"You shall have a ride in it some day. At present we are in a hurry."

"Come in at once, señor. I will not keep you waiting. Señor Gomez would wish me to be entirely at your service."

While the boys enjoyed the substantial meal set before them, two men on ladders removed the debris from the Gadfly's wings; others scrubbed off the lower part of the hull the mud and green slime that had collected upon it during the days it had been in the Indian village. After breakfast the boys themselves plugged up the holes, oiled the levers and controls, and filled the tank. The major-domo supplied them with a new store of food, and a couple of lanterns in case they were again benighted. With some difficulty Pedro persuaded him to lend the map which Señor Gomez had shown them.

"Shall we take Bola?" said Derrick when they were ready to start.

"Won't he be in the way?" Pedro asked.

"I don't think so. There's plenty of room for him and Gomez too. Besides, he may be useful when we get back: you never know; and he'll be glad to see Pat when he's released."

"Ah! I'm afraid it's 'if' rather than 'when.' But you're right: we'll take him. He's not a bit serious; might have been riding in the Gadfly all his life."

The preparations for the flight had been watched with keen excitement by the people of the estate. They left their work and gathered around, breaking into little cries when they saw the three strangers go one after another into the interior of the mysterious vessel. They gasped when it rose slowly into the air, and remained like fixed images, staring upward until it vanished.

Derrick had made up his mind that as speed was all-important, it would be necessary to rise to great heights. The higher the Gadfly flew, the greater would be her velocity in the downward sweeps and the greater the horizontal distance she would cover. One by one he opened out the compartments and flooded them until he had only three in reserve. With the map outspread before him and the compass at his elbow he set his course straight for the Madeira river.

The machine rose with great rapidity, Derrick's sensation being that the earth was slipping away beneath him. Great stretches of forest dwindled to the size of copses, broad streams to mere threads. Every few seconds Pedro called out another mile of altitude. At two miles he closed the air inlets; at five Derrick began to pump air to check the ascent; but the machine had risen nearly two miles more before the upward movement ceased. Then within two minutes they were falling at the rate of more than a mile in five seconds. Remembering certain calculations already made Pedro shouted:

"A thousand miles an hour!"

Derrick's reply was to flood several of the compartments, and gradually to move the elevators in order to reduce the angle of their descent. Still they swept downward, but at diminishing speed. Keeping up a steady pressure on the elevator Derrick slowly flattened out, and when the machine again began to rise he calculated that it had travelled between thirty and forty miles from its starting-place at the hacienda.

Away to the right he now saw a silver streak stretching almost due north and south. This must be the Madeira, the river up which they had crawled in canoes, only a few weeks before, sometimes at the rate of less than ten miles a day. How hard it was to realise that they were now following its downward course at almost as many miles a minute! Soon, as they came to the bottom of another downward loop, they caught sight of a collection of houses on the bank.

"San Antonio," Derrick called.

He steered along the course of the river, and presently saw, far below, its junction with another broad stream, the Upper Amazon. Swinging round to the east, he resolved to make a crow's flight instead of following the numerous and enormous coils of the river. He cut straight across them, saving half the distance actually traversed by the stream. Even at immense heights it could always be discerned as a ribbon gleaming on the dark ground, when all other landmarks failed.

"Keep a look-out for steamers," said Derrick.

"Then you mustn't go higher than about five miles," replied Pedro. "It's quite impossible to distinguish anything at a greater distance."

"We must chance that. We must rise high if we are to make sure of getting to Para in time. The best thing is to go straight ahead at our best speed. It doesn't matter if we reach Para before Gomez, but our whole scheme might fail if we arrived after he'd sailed."

The Gadfly raced on in her switchback flight; at each descent falling to within three miles of the earth. Pedro once called out that he saw the smoke of a steamer, but when Derrick dropped a mile or so lower, and the vessel could be seen more clearly, Pedro recognised by the spreading wake at its stern that it was proceeding upstream.

After the machine had risen several times to an altitude of something like ten miles, the boys became aware of increasing cold. By stopping the inflow of air, and remaining only a few seconds at extreme heights, they had managed to retain hitherto a considerable proportion of the heat with which they had started. But after repeated ascents it was inevitable that the outer cold should penetrate, in spite of the asbestos lining.

They were shooting upward with four of the five compartments engaged when Pedro noticed that the barometer was falling very slowly. For the first time with this enormous force at work the machine was slowing down without the use of the air-pump.

"We are rising, but not so quickly," said Pedro.

"I wonder why," said Derrick. "I hope to goodness the solution doesn't lose its power after a few hours."

He flooded the remaining compartments. "How is it now?" he asked.

"The barometer is falling a little quicker. But no; it's not falling at all now; it's stopped; it's beginning to rise. The machine is dropping. You're sure you're not pumping in air by mistake?"

"Quite sure. But-goodness above! did you hear those balls rattling? They are dropping down; the force isn't working; we've got some more crystals: pitch them into the tank at once."

The machine continued to fall; moment by moment the levity balls clicked to the bottom of the compartments. Derrick felt bewildered, dazed. The possible loss of power in the solution had once crossed his mind but he had had no experience of it, and the fact that the fresh crystals had no effect set him beating his wits for another explanation.

"What's our height?" he asked suddenly

"Ten miles."

"Ah! The water's freezing on the balls."

He threw an agonised look over his shoulder at Pedro. There was an instant's horrified silence; then the ominous click of another ball galvanised Pedro's wits.

"The Primus!" he exclaimed and picked up the stove. It was already filled with paraffin. "Where's the methylated spirit?" he called.

"No time for that!" cried Derrick. "Strike a light and pump up."

Pedro at once struck a match, set light to the oil, and held the stove up so that the broad yellow flame licked the bottom of the levity compartments.

Meanwhile Derrick had levered the control so as to get the maximum elevation on the tail-plane but in the rarefied air it had at first almost no effect in reducing the angle of fall.

"Under the forward compartments" cried Derrick. "The nose is dropping."

In a few seconds they heard the balls rattling up to the roof. The heat of the flame, acting directly on the thin steel floor of the compartments, had thawed the film of ice that had formed on the balls.

The Gadfly was once more on even keel; had her downward flight been checked? Pedro ordered Bola to hold the flaming stove under the second compartment, while he worked the pump. Glancing at the barometer he shivered as he saw that they were still plunging earthward at meteoric speed. With impassive face the Indian moved the flame from the second compartment to the third. More and more balls went flying to the roof, but to Pedro, looking out of the window, the earth seemed to be rushing up towards him. What had been a dark, blurred, featureless expanse was now changing its aspect, breaking up, as it were, into a patchwork. Here was a blackish blotch, spreading like an ink-blot upon paper: evidently a forest. Here was a lighter patch that might be a plantation, or a village, or perhaps a bare hillside. Moment by moment the patches enlarged, became more clearly defined. That looped ribbon widened; it must be the Amazon. Tiny specks upon it: were they canoes, or steamers? Would this precipitous descent not be checked until the Gadfly plunged into the river, or crashed upon the unyielding earth?

Pedro gasped with relief when he realised that they had now dropped out of the region of freezing cold. The balls were clicking like castanets against the roof; more and more compartments were coming into play. He glanced at the barometer: it indicated three miles above the earth. He looked down again through the window: the objects beneath were no longer growing more definite. The fall was checked; the nose of the machine was gradually rising; once more it was on the upward climb.

The boys mopped their clammy brows. The interior reeked with the fumes of paraffin.

"Open the taps,"' said Derrick, through his parched lips.

And as the air whistled through the inlet they drew long breaths.

Derrick had learnt a lesson.

CHAPTER THE SIXTEENTH - A SEA CHASE

DERRICK continued to ascend only for a minute or two.

"I must have a rest," he said. "I feel absolutely done up. And we ought to let the machine get thoroughly warm again. Look out for a landing-place, old man."

Below them now nothing was to be seen but forest stretching far on both sides of the river. There was no space large enough and clear enough for a safe descent. For some twenty minutes Derrick proceeded in a series of short climbs and dives, covering about as many miles. Then Pedro caught sight of a town on the right bank, at the confluence of the Amazon and a tributary. The larger river was edged with a stretch of white beach.

"You can land on the beach," said Pedro.

Slowly the Gadfly descended. The features of the town became definite. Backed by sharp hills, it fell to the river in a series of terraces, its houses, white, yellow and blue, gleaming in the sunlight.

"It must be Santarem," said Pedro. "You remember we touched there on the way up."

As the machine floated gently down, people were seen gathering in the streets, gazing up at it.

"Remember the skid's broken," said Pedro. Derrick nodded. Checking the motion until it was barely perceptible, he brought the Gadfly to rest on the sand. The bank was lined with excited spectators.

"Bola, we'll leave you in charge," said Pedro.

"Don't let anyone come in."

They opened the door, stepped out, closed the door behind them, and walked up the beach. The crowd pressed around them, plying them with questions, Pedro good-humouredly fending them off.

"Yes; it's a new flying-machine-flying-fish if you like. You didn't hear the engines? Well, there aren't any...Our motive-power? That's a secret...Yes, we are the inventors...No, we do not take passengers for joy rides. In fact, we're in a hurry: important business."

Edging their way through the inquisitive bystanders, they walked up into the town, bought some fruit and chocolate, and returned. On their way back they inquired at the steamer office whether the Capella had passed down, and learnt that she had left on the previous morning. The river being in flood, she would probably arrive at Para that day.

A small crowd had collected on the beach by the machine. Among them was an officer of gendarmes and two of his men. The door was still closed. The officer accosted the two boys, bringing out a notebook.

"This is your vessel, señores?" he said.

"It is," replied Pedro.

"An airship, no doubt."

"You are quite right, señor capitan."

"Have you a permit to fly?"

"Is it necessary?"

"You do not know that? Of what nationality are you?"

"I am a Bolivian. Permit me," he added in English, "to introduce my friend Mr. Derrick Moore. The señor capitan speaks English?"

"I do not. This is very irregular. I must ask for your passports."

Pedro turned to Derrick, as if to explain that the officer spoke no English.

"This excellentissimo capitan blighter is going to stop us," is what he really said.

"I don't think," said Derrick in the same vein. "If the señor capitan will allow us to enter the machine..."

"You have your papers there? Very well. I must accompany you!"

"Certainly, excellentissimo," said Pedro, smiling. Derrick entered the machine first, then the officer, Pedro last. The officer glanced curiously round.

"That is our barometer," said Pedro, casually working the pump handle. "A useful instrument, as the señor knows: it tells us how many miles up we are."

"Miles, señor?" asked the incredulous officer. "Oh yes; we think nothing of ten miles or so. And that, you perceive, is our clock: also very useful. It tells us how many miles a minute we fly."

"Miles, señor?"

"Oh yes. We think nothing often miles a minute."

"Caramba!...What is that?"

The levity balls had begun to click. Derrick, seated negligently in the pilot's place, had opened two compartments. Through the window the officer saw the brightly-coloured houses apparently moving slowly downward. He leant against the side and peered out.

"Caramba! We are rising," he cried. "What is this, I demand?"

"The force of levity, señor capitan," said Pedro. "I am sorry to put you to any inconvenience, but we are engaged upon a most urgent mission; every minute is precious, and we could not wait for formalities. I don't suggest that you are exceeding your duty, but—"

"This is infamous!" cried the officer furiously.

"You carry me up into the air against my will. Por Dios the height is already stupendous." He showed signs of nervousness. "I demand that you let me down instantly. To kidnap an officer of gendarmes is felony and you shall...ohé! The town is almost out of sight. Stop! Descend! I shall be sick!".

"You are quite safe, señor capitan. This is your first air-flight? It will be a novel experience, and I am sure you will find it really quite pleasant. Seriously, we could not spare a minute. We will set you down safely before long. Don't make a fuss."

The officer relapsed into a sullen silence. Derrick flew a few miles down the river until he came over another stretch of beach. Here he descended. Pedro politely ushered the officer out of the machine, and left him to make his way back.

"He'll brag about his trip all over Santarem," said Derrick, laughing. "Now for Para, and I hope we'll have no more interruptions."

He set his course eastward for the seaport, about four hundred miles away as the crow flies. By this time the machine was thoroughly warm again, and he ventured to rise to ten and even fifteen miles before beginning the downward glides. In less than an hour they should reach their destination.

After passing Almeirim, on the left bank, they diverged from the main stream of the Amazon and struck to the south-east, across the maze of islands between the great river and the Rio Para. The Gadfly continued its undulating flight with a smoothness that was almost monotonous. Presently the white walls and red roofs of the port hove in sight. Two or three vessels were moving along the broad river, and the boys wondered which of them carried Señor Gomez, or whether he had already arrived. Farther out were innumerable small craft. Forest encircled the town.

"We can't risk being detained again," said Derrick.

"I'll land you near the town, and remain with the machine while you make inquiries at the shipping office. If there's any sign of interference I'll rise and hover about until you come back."

He chose for his landing-place a small clearance in the woods outside the town. There were only a few insignificant huts in the vicinity, and the natives who had watched the descent of the machine held aloof timidly.

Pedro was back within an hour. "Gomez has gone," he said.

"That's strange. I made sure we'd outrun a river steamer."

"So we have. The agent at the shipping office told me that he left the steamer at Santarem, and took a fast motor launch. He was afraid of missing the liner, and only just caught her. She sailed before dawn this morning, and is well out to sea by this time."

"What port is she bound for?"

"Lisbon."

"Well, we shall have to pelt after her. There's nothing else to be done."

"I anticipated that. Thought it just as well to send Gomez a wireless."

"Good man! What did you say?"

"Alvarez and Moore chasing you in Gadfly. Matter of life or death."

"That will stir them up. They won't be quite unprepared. But they'll get a bit of a surprise all the same when they see us. What's the name of the liner, by the way?"

"The Ariadne."

"Well, let's make a start. We may have no end of a hunt."

The machine soared above the trees.

"It's a pity we can't fly horizontally without so much climbing and diving," Derrick said. "You and Bola must keep a good look-out, or we may easily miss the vessel."

He rose to the height of five or six miles, and then began a long downward glide which brought them over the lagoons to the mouth of the river. The broad tawny flood was dotted with canoes and river schooners with red and blue sails, but there was no sign of a liner. Then Derrick set his course for the open sea, flying north-east, and rising no higher than two miles, so that nothing on the surface should escape the eyes of his companions. There were two vessels away to the south-east, little more than specks in the distance; but referring to his map Derrick guessed that they were working up the coast from Pernambuco or S. Luiz. Northward and north-east stretched a bare waste of water, gleaming like a sheet of corrugated steel.

Alternately rising and falling, the Gadfly sailed on, Derrick steering by the compass, as nearly as he could judge, along the Para and Liverpool route. The necessity of keeping reasonably low prevented him from running at as high a speed as he would have liked, but he calculated that he had covered a horizontal distance of eight or ten miles before Pedro sang out that he saw a vessel far away on the port side. In a few seconds Derrick brought the machine down until it hovered fifty or sixty feet above the steamer's deck.

"I don't think she's our vessel," said Pedro; "not large enough."

"Better ask," said Derrick.

"I wish we had a megaphone. She's out of hailing distance already."

"Another disadvantage of our not being able to fly horizontally. I must go up again and overshoot her when I come down. Open the door and be ready to hail her the moment we are vertically over her."

The Gadfly shot up, and Pedro smiled as he saw the amazed looks on the faces of the crew and passengers, who had crowded on deck and were gazing upward. Gliding down so as to come to rest about a hundred yards ahead of the vessel, Derrick held the machine stationary, forty feet above the funnel.

"Are you the Ariadne?" shouted Pedro from the open door as the steamer came below, slowing down.

"No. Who the deuce are you?"

"No time for introductions," Pedro called. "Bon voyage!"

Once more the Gadfly ascended. When she came down again, two minutes later, the vessel was merely a smudge on the waste.

Not long afterwards Bola, looking out through the starboard window, cried that he saw a smoke-canoe, his name for a steamer. Pedro went to his side, and was just able to distinguish a tiny spot on the horizon. Derrick slightly altered his course. In two minutes it could be seen that the vessel had two funnels. In yet another minute, executing the manoeuvre he had already practised, Derrick had the Gadfly hovering almost in the liner's smoke.

"Are you the Ariadne?" shouted Pedro to the captain on the bridge.

"Ay, ay. And you're the Gadfly?"

"Ay, ay, sir. Heave to, if you please. We can't keep pace with you."

He could just hear the tinkle of the signal bell as the captain moved his lever. But before the vessel lost way she was two or three cables' lengths ahead, and Pedro could not make his voice heard. Then she began to back and was soon directly below the Gadfly. Decks and steerage were packed with upturned faces.

"Sorry to delay you, captain," said Pedro, leaning out. "Is Señor Gomez on board?"

"He is." One of the passengers joined him on the bridge. "We got your wireless."

"Can we land on your deck?"

"Good sakes, no! The very idea! You'd smash us up."

"Not at all. We can reduce our weight to nothing."

"Toodle-oo!" scoffed the captain. "D'you think I'm cracked?"

"The captain of a liner, sir? I'll prove what I say. Send her up a bit, Derrick."

Derrick flooded one compartment. The machine soared up some three hundred feet, then sank slowly to its former height.

"Well now, I guess that's cunning," said the captain.

The passengers cheered. Pedro saw Señor Gomez turn to the captain, smiling, with an air of "I told you so."

"We can come down without crushing a fly," said Pedro.

"I won't take that risk," said the captain, "but I'll trust you some way. Ahoy there! clear the upper deck. Cover it with tarpaulin and straw. You up aloft there, wait. I've drifted a bit; don't you dare to come down until the deck is plumb under you."

By the time the captain's orders were carried out Derrick had manoeuvred the machine to a position immediately above the stern of the vessel, and when all was ready he put her nose down a little more and glided over the deck. The ring of passengers watched breathlessly as she sank gently down and settled on the straw without jerk or jar.

"Say that's A-one handling," said the captain. "I guess I'll be proud to shake hands with your pilot."

Pedro and Derrick stepped out on to the deck amid a salvo of cheers. The excited passengers began to mob them clamouring for explanations.

"Way there!" shouted the captain. "Let the gentlemen through to the bridge. And stand clear of that machine. I won't have any meddling aboard my ship, nor accidents neither."

The boys went up the ladder, and were warmly greeted by the captain and Señor Gomez in turn.

"I thought Mr. Gomez was pulling my leg when he told me the meaning of your wireless," said the captain. "But your Gadfly's a marvel; you may take my word for it. You'll want to converse: a matter of life or death, you said. I wouldn't have stopped my engines for anything else."

"We're much indebted to you, captain, said Derrick. "Perhaps you would like to look over the machine while my cousin explains our errand to Señor Gomez."

"I'll go with you, right now," said the captain heartily. He summoned the first officer to the bridge, and followed Derrick into the machine, to the unconcealed envy of the spectators.

CHAPTER THE SEVENTEENTH - A LAST APPEAL

SEÑOR GOMEZ blazed with the sudden anger of the Latin races when he heard of the plight of his old friend and partner Roving Pat.

"That dog Miguel Mollendo is not fit to live," he cried. "Murder Pat Heneky! I loved the man, the kindest, dearest companion, more like a brother to me. I have mourned him as dead, and now, to hear that he is alive makes my heart leap with joy. Alive, but in danger of death through the villainy of that sly sneaking traitor! You did well, señor, to pursue me. My business, it is nothing. I would fly from the ends of the earth to save my friend. But shall we be in time? Even with your wonderful machine can we reach La Paz before the fatal moment? I am distracted, torn with anxiety and fear."

"We can do it, barring accidents," said Pedro. "We have only taken about five hours, including stoppages, to come from your hacienda. We shall save time on the way back. Our one fear was that you might hesitate to venture on the journey."

"How could I hesitate with such examples before me? I am ready now, this instant."

"Then if you will get your baggage up I will tell my cousin."

At the pressing entreaty of the captain, Derrick consented to remain long enough to take a quick meal with his companions. Then they re-entered the machine.

"Your quarters will not be very comfortable, señor," said Pedro to Gomez, apologetically.

"More comfortable than Pat Heneky's cell," was the answer. "I pray you, let us go."

The captain, informed of their errand, shook hands with them heartily and wished them God-speed. He had already started his engines when the Gadfly rose from the deck and the travellers were sped on their way by the ringing cheers and waving hats of the passengers. In little more than a minute the machine was out of sight.

Contrary to Pedro's expectation, the return flight was more difficult than the outward journey. Then, it had been safe to follow the course of any stream: it must lead sooner or later to the main river. But now when once the Amazon itself had been navigated, they had to be constantly on guard against taking the wrong turning, as a traveller on land might have said. In point of breadth, some of the tributaries were as considerable as the main stream itself. Derrick had to watch his course and take his bearings more carefully, with frequent reference to map and compass. And Señor Gomez, though he had been up and down the Amazon scores of times, was not able to lend any help. The aspect of the country seen from above was strange to him; it changed from moment to moment as the Gadfly rose and descended; and he confessed that he was utterly baffled, even when the map was before him when he tried to pick up landmarks that otherwise he would have easily distinguished.

In the first hour or two of the flight Derrick rose to great altitudes in order to attain a very high rate of speed on the downward glides. But presently he was dismayed on discovering that the machine was no longer air-tight. At heights above the three miles all the occupants of the Gadfly found that breathing became difficult and they were attacked by dizziness. Derrick suspected that in rising rapidly to immense altitudes, and using the levity force at full strength to check the downward swoop, he had strained the framework of the machine, and developed small fissures through which air escaped when the pressure of the atmosphere without became low. No longer daring to ascend so high as formerly, he had to reconcile himself to the inevitable loss of speed. On the other hand, he had become so expert in the manipulation of the controls that he was able to attain a far greater speed in a given rise and fall than in the earlier attempts. The course of the machine was now a series of gentle curves, a switchback, indeed, but of a less precipitous kind, with no sudden checks at the top and bottom. Even under the limits Derrick felt bound to observe in regard to altitude, the Gadfly, gliding like a huge bird across the continent, covered a horizontal distance of nearly three hundred miles an hour.

At the beginning of the flight Señor Gomez, clutching one of the upright struts, gazed out of the window, wholly engrossed in the changing scenes below. After a time he sat down with his back against the curving flank of the machine, and watched Derrick's quiet operations.

"Wonderful!" he said. "So easy! And what an advantage it is to have no disturbing clatter of engines! Tell me how you met my old friend Pat Heneky. But no: you are both too much engaged: the story will wait."

"But we can listen, señor," said Pedro. "Tell us about Mollendo."

"You are sure? I would not distract you. Very well. Mollendo, a plausible man, was a partner with Heneky and me in a prospecting expedition through unexplored country not a great distance from your hacienda. It was seven years ago, before your father started his mine. We had gathered a considerable quantity of specimens of mineral-bearing rocks, in which we suspected the presence of copper and gold. Our food ran short; the district at which we had arrived was very deficient in game, and one day, at Mollendo's suggestion, Heneky and I set off in different directions in the hope of replenishing our larder, leaving Mollendo and the Indians at our camp.

"It was was an hour or two before I had any luck, and then I was only able to shoot two or three birds. I hurried back and to my great surprise found that Mollendo had had all our belongings packed up, and seemed to be on the point of striking camp. To my questions he replied that he had only made ready for departure as soon as Heneky and I returned; but I could not help suspecting from his manner, and from the truculent looks of the Indians, that he had hoped to get away while we were still absent, and had bribed the Indians to fall in with his plan.

"All the rest of the day I looked anxiously for Heneky's return. At nightfall he had not come. I was not at first alarmed for him; I thought he had been unlucky in his quest of game, but being a dogged fellow had determined not to come back empty-handed. In the middle of the night I was suddenly awakened by some one entering my tent. Before I could rise I was seized: two Indians tied my hands and feet together, in spite of my struggles, and hauled me into the open. Then Mollendo showed his true character. He taunted me as I lay on the ground, and said that he would leave me to be found and released by my dear friend. I knew by his manner of speaking that he was jealous of the close friendship between Heneky and me. And then they struck my tent and folded it and I saw them march off in the moonlight, carrying' not only our specimens, but our maps, money and everything, leaving nothing but my rifle and a little ammunition.

"Imagine my feelings. I lay there helpless, a prey to innumerable anxieties and fears. Should I fall a victim to some prowling beast? Had some mishap befallen Heneky? Would he return and find nothing but my bones and the rags of my clothes? It was some time before I even attempted to release myself. Then I strained in vain at my bonds, and lay exhausted in impotent despair. Insects stung me, little creatures crawled over me, and I felt a mad wish that I could talk to them and persuade them to gnaw the cords that held me down.

"That idea suggested the plan by which I at last gained release. My wrists, tied across each other, were out of reach from my mouth because my elbows were bound to my sides. But I found that by vigorous effort I was able to slacken these middle cords until I could just raise my wrists to my teeth. And then I gnawed like a rat until I had bitten through one strand, and in a few seconds after that my hands were free. It was then easy to release my feet, and I hastened to the stream that flowed by our camping-place and quenched my burning thirst.

"What was I then to do? I had no food. I dared not seek for any, lest Heneky should return during my absence. All that day and the next night I waited, hoping to see him come into the clearing from among the surrounding trees. Then I set forth to try to track him, but I had no skill; tracks in the jungle are at any time hard to follow; and I returned baffled. Life is dear; I could not starve; and at last I wandered away at a venture, to find some fruit-bearing tree that would give me sustenance.

"I need not tell you of my sufferings during the next two days. I kept myself barely alive until I stumbled upon a village of friendly Indians. At my urgent entreaty they sent out parties in search of my friend, but I could give them no clear directions, and they found no trace of him. By their aid I was enabled to reach the nearest town, where I set on foot inquiries both for Heneky and Mollendo. From that time until this day I had never heard of either of them, which is not surprising when you consider the vast spaces of this continent, and the fact that my inquiries were prosecuted in Brazil, and not in Bolivia."

"I wonder why Pat supposed that Mollendo had murdered you?" said Pedro.

"I cannot tell. We shall know that when we meet. I am rejoiced that Pat did not suspect me of deserting him with Mollendo: he trusted me."

During the few minutes occupied by Señor Gomez's narrative the Gadfly had made steady progress. But Derrick realised that it would be dark before they reached La Paz. He did not relish the idea of flying in darkness, but as Pat was to be shot next day, perhaps at a very early hour, he felt that it would be unsafe to rest during the night. And though so considerable a town as La Paz would be distinguishable by its lights, yet it might not be easy to discover the valley in which it lay among the mountains, and the search might take a long time.

The Alvarez hacienda lay almost on the direct course to La Paz, and Pedro suggested that they might alight there for a meal, and to learn if there had come any further news. It would mean the loss of only a few minutes. Further, as Bola had travelled more than once between the hacienda and La Paz, he might be useful in pointing out landmarks on the way.

Unluckily, for the first time since Derrick had started flying, the earth was obscured by dense clouds, rendering his map useless. He dared not rely wholly on the compass, and thought it best to descend through the clouds, take his bearings, and if necessary alight until the sky had cleared. At the height of about three thousand feet above the ground he found himself caught in a thunderstorm, and hastily ascended again; it seemed safer to ride above the storm than below it. He checked the Gadfly's motion, and for a while hovered at the height of four miles, watching the lightning playing far beneath, and listening to the rolling reverberations of the thunder, which seemed strangely gentle.

The storm gradually abated; rents appeared in the dark curtain of cloud; once more the voyagers obtained peeps of the earth; the flight was resumed. But some little time had been lost; and though it was still only dusk in the higher altitudes, when the Gadfly, after much casting about, arrived in the neighbourhood of the hacienda, darkness lay upon the valley. Derrick had intended to land at the usual spot, about two hundred yards from the house; but finding himself some distance short of it, at the edge of the cultivated area, he decided to come down there, in order to avoid another long climb.

When the machine was at rest, Pedro went on alone towards the house. Lights were just appearing in the windows. As he crossed the front below the veranda, he was amazed to see two or three men in uniform moving in the principal room. He slipped into the shade of a dense hibiscus, and was still more astonished when he saw, among the uniforms, the well-remembered figure of Juan the treacherous guide. Giving up his intention of entering by the veranda door, he hurried round to the servants' quarters at the back, and tapped lightly on the door of the room appropriated to his mother's major-domo.

Five minutes later he was running at full speed to the Gadfly. On the morning of that day, Juan had arrived in the company of half a dozen gendarmes. They had announced that the estate and mine were sequestrated to the Government, and that they would take up their quarters in the house until the new owners entered into possession.

"Mollendo, I suppose," said Derrick when Pedro, in a fiery indignation, had given the news.

"I don't know," replied Pedro. "The men didn't know. But if you and Señor Gomez will come with me we will turn the wretches out. The servants will help us. The mine-workers will be with us to a man."

"We can't spare the time, old fellow," said Derrick.

"It's one more reason for hurrying on to La Paz. When we have got Pat released, we shall have no difficulty in settling the other matter. Aunt Bertha is not at home, of course."

"No."

"Then we shall no doubt find her in La Paz, and her friend the President will settle Mollendo's hash. It will all come right in the end."

The Gadfly rose silently into the air, and was soon skimming the tops of the mountains. Neither map nor compass was of much avail now, and Derrick was not familiar enough with the firmament to get any great assistance from the stars. He flew up and down, round and round, while his three companions kept a sharp look-out at the windows for the lights of La Paz. The necessity of rising very high to clear the mountain-tops rendered the search long and difficult. More than once they were deceived by gleams which, when the machine descended, proved to be only reflections of the starlight upon the snow. It was nearly two hours before they caught sight of a large irregular luminous patch which could only be accounted for by the lights of a collection of houses.

"You know the town," said Derrick to Pedro. "Where do you suppose Aunt Bertha will stay?"

"Most likely with her friends the Villanovas. Their house overlooks the racecourse at the northern end of the town."

"Then if we come down on the racecourse you can find your way?"

"Easily. But we may be seen."

"I don't think so. The people in the streets won't be able to see much beyond the housetops, and if we can drop down behind the grand-stand we ought to be safe. Anyhow, I see nothing better."

He let the machine down cautiously until it was low enough for Pedro to take his bearings; then rose again slightly to glide down to the place at which he aimed. Pedro's judgment was slightly at fault, but this turned out rather an advantage than otherwise, for the spot at which the Gadfly actually descended was a little fold in the hills behind the racecourse, where it might with luck remain undiscovered even in daylight.

Leaving Bola in charge of the machine, the other three lost no time in making their way to the house of Señor Villanova. There, as Pedro had surmised, his mother was staying. After a crowded five minutes of explanations and introductions the señora told of the failure of her errand. The President was away hunting in the south. She had tried in vain to communicate with him by telegraph. She had sought an interview with the Minister of the Interior, but had been refused. Señor Villanova was himself helpless. He explained that he was in a rather delicate position. The President's frequent absences on hunting expeditions were leading to great laxity in the administration. There were persistent rumours of revolutionary designs, and it was whispered that the Minister of the Interior and the Secretary for Mines were both implicated. As a close friend of the President, Señor Villanova feared that any strong action on his part would lead to his summary arrest.

"And Pat?" said Pedro.

"He is to be shot at dawn to-morrow," said the Señora.

"Then we are still in time, thank Heaven!" said Señor Gomez. "I will go myself at once to the Minister. No doubt my young friends will accompany me. When I tell who I am—"

"But can you prove your identity?" asked the Señora.

"I am not known in La Paz, it is true; but I have my papers, my passport for Europe, and these will be sufficient to induce any right-minded man at least to delay the execution until further proof, if necessary, is obtained. Mollendo shall find that I am very much alive."

Half an hour later Señor Gomez and the two boys were at the door of the Minister of the Interior. To their request for an interview the servant replied that his Excellency was at dinner and could not be disturbed.

"Take him my card," said Gomez.

Beneath his name he wrote in pencil: "Supposed to have been murdered."

The servant was away some minutes. When he returned it was to report that the Minister was engaged, and could not attend to business until the morning. And then the scandalised flunkey found himself pushed aside, and the three strangers hurried through the corridor to the open patio, where three men were at dinner. One of them started up angrily; the second leaned back in his chair with a sardonic smile; the third stared blankly. It was Miguel Mollendo.

"What is the meaning of this impertinent intrusion?" demanded the man at the head of the table.

"You are the Minister of the Interior?" replied Gomez. "Then I tell you, señor, that I have come to prevent a judicial crime, for which that man"—he pointed an accusing finger at Mollendo—"is responsible. I am the man for whose supposed death my friend Pat Heneky has been condemned. That man was the accuser; I charge that man Miguel Mollendo with—"

"Silence!" shouted the Minister. "This is unparalleled insolence. Señor Mollendo, do you recognise this-this unmannerly fellow?"

"I never saw him before," said Mollendo coolly.

"Liar!" said Gomez. He afterwards acknowledged that the unexpected sight of Mollendo had enraged him beyond control.

"Silence!" cried the Minister again. "I will not hear you. If you do not instantly withdraw I will have you and your associates arrested for conspiring to defeat the ends of justice. The criminal has been convicted after due trial under the laws of the Republic. This intrusion is equally insulting to the State and to me personally. Go, before I summon the gendarmes."

Gomez had now had time to collect himself. He realised the false position into which his outburst had thrown him. The Minister, if innocent, might reasonably resent the intrusion of a hot-tempered stranger; if an accomplice of Mollendo's, he had been presented with a weapon which he had shown himself quick to use. There was a moment's silence: then Gomez turned to the boys.

"Let us go," he said.

CHAPTER THE EIGHTEENTH - THE GADFLY'S STING

IN the chill grey mist of a cheerless dawn a small company of privileged spectators was assembled in the courtyard of the prison. There was to be an execution: not the public execution of some "poor Indian with untutored mind," whose end might afford amusement to the populace, but a more private ceremonial, to which only a select few would be admitted. Certain of the town's notabilities were there, persons of importance, who, though the hour was early and the air nipping, had come in good time for the spectacle, as they, or others of different tastes, might have gone to the "first night" of a drama.

Wrapped in warm coats, gloved and stoutly shod, they paced the rimy stones, throwing an expectant glance now and again at the closed door in the prison wall. A stir of interest was noticeable when the door was at last opened, and there came forth three figures that were to lend official countenance and dignity to the scene. Respectful salutations were made to that excellentissimo señor the Minister of the Interior, and the somewhat less august personage, the Secretary for Mines; and if there was; a shade less deference paid to the third member of the party, a man of great stature and conscious self-importance, it was because Señor Miguel Mollendo was not so well known as the others and had not yet attained to office in the State.

A warder closed the door behind them. They greeted individuals in the company: smiles were exchanged as they caught sight, through the mist, of spectators perched upon the neighbouring housetops; then they posted themselves in line, the rest grouping themselves in their rear. The hush of expectation dominated the courtyard.

The door swung open again. A squad of gendarmes, armed with rifles, marched into the yard behind their officer, and at the word of command formed up and stood at ease. A minute or two later appeared the Governor of the prison, and behind him, enclosed among four warders, a pale meagre figure, unkempt, unshaven, barefoot, his hands manacled. A slight smile, mocking, contemptuous, wreathed his firm lips, as he glanced around the assembly. His light grey eyes rested for a moment inscrutably on the fat face of Señor Mollendo, then were drawn upward suddenly; no one but him, probably, caught sight of a white handkerchief waved by a hand on a neighbouring roof. It flashed once, twice, then disappeared. The prisoner seemed to hold himself more erect: he walked with a firm step to the blank wall opposite the doorway, and faced round. A warder approached him, holding a strip of cloth; but the prisoner shook his head, smiled again, murmured a word or two. The warder looked at the Governor; that official shrugged his shoulders, and signed with his hand. The man pocketed the rejected bandage, and stood among his fellows.

The silence was abruptly broken by the voice of the officer of gendarmes, uttering sharp curt words of command. The men stood to attention, quickstepped fifteen paces, and formed a line facing the prisoner. "Load!" cried the officer.

But at that moment someone uttered a brusque exclamation; all eyes were turned skyward; even the gendarmes stayed their hands. Above the housetops, indistinct in the mist, loomed a dark object like a monstrous flying fish. It was circling in a short spiral, swooping towards the ground. No one noticed the quickly changing expression of the prisoner's face-wonder, hope, delight.

As the strange object descended, its shape became more clearly defined. It hovered like a vulture about to pounce; then, with a suddenness and a rapidity that bereft the spectators of breath, it dropped vertically into the courtyard, straight upon the gendarmes, in the suspended act of drawing the cartridges from their belts. Discipline went to the winds; the men skipped and staggered out of the way and scattered in all directions, some of them dropping their rifles. And while the spectators were still silent in the grip of a paralysing astonishment, the disturber of ceremony came to rest with a tremendous bump.

The next half-minute was crowded. The door of the Gadfly flew open; a voice called "Pat!" The prisoner took three leaps across the yard. With his manacled hands he could not help himself; but Pedro and Bola, leaning down, caught him by the shoulders and began to lug him in. The moment his feet were off the ground the machine began to rise, slowly. But now there rang out an explosive cry: a burly form dashed from among the stupefied company, flung himself forward, and caught a grip of Heneky's bare feet. The sudden weight checked the Gadfly's ascent, for Derrick was employing little force until assured of Pat's safety. The machine rocked; Pedro and the Indian staggered; Heneky was almost dragged out of their hands; but they set their feet firmly against the stanchions of the framework, and Señor Gomez sprang to assist them. With great heaves they hauled Heneky half through the doorway, Mollendo still clinging to his feet.

The machine was now as high as the housetops; it was too late for the big man to let go, and he dangled in the air, squealing with fright. It seemed that in a few moments he must inevitably lose his hold and plunge among the swaying, agitated groups below. Derrick felt that he must take a risk. Charging another compartment, he left his seat and dashed to the rescue. While Pedro and Bola kept a tight hold upon Heneky, the upper part of whose body was now bent over the bottom of the doorway, Derrick and Gomez leant down, and each seized with both hands a wrist of the shrieking wretch. The strain upon Pedro and Bola being thus relieved, they were able to haul Heneky by degrees farther through the doorway until he lay full length, only his feet projecting. To these Mollendo still clung convulsively. Now that Heneky was safe, all four were free to give their whole attention to the big man. Two of them dragged him by the wrists, the other two got their hands under his armpits; Heneky freed his feet with two or three convulsive kicks; and in another half-minute the huge bulk flopped inert upon the floor of the machine.

Then Derrick sprang back to the controls, and checked the upward glide, which was becoming too fast for the Gadfly in its present precariously un-airworthy condition. Heneky turned over; a happy smile illumined his rugged face.

"'Tis a proud man I am to-day," he said huskily.

"Sure she's a world's wonder. Ah! José, José!"

And Derrick could not forbear smiling when he saw Señor Gomez fling his arms around his old friend and, in the Latin way, kiss him repeatedly on both cheeks.

There was a hurried consultation. A minute later the Gadfly dropped down into a stretch of thick scrub close by Señor Villanova's house. Señora Alvarez and her host had been anxiously on the look-out, and they were on the spot almost as soon as the machine alighted.

"You have him safe?" cried the señora.

"Yes, and Mollendo too," answered Pedro from the doorway. "He wouldn't let Pat go."

"Let me go now," cried Mollendo, who had scrambled to his feet as soon as the machine touched the ground.

"Shall I?" asked Pedro of the rest, laying a detaining hand upon the big man.

"Ask Pat," said Derrick.

"Sure we'd be the better of taking him with us," said Heneky drily. "The three of us are met together; believe you me, there's a mighty power of things to be said."

Mollendo tried to wrench himself from Pedro's grasp, clamouring to be let go. But with a quick jerk of his leg Pedro tripped him up; he fell prone, and Bola's deft hands began to lash him to a stanchion.

"Now, we've no time to spare, madre," said Pedro. "You may be sure they've watched our flight, and when they see we've come down they may send mounted gendarmes full gallop after us. They had better not know that Señor Villanova is mixed up in this, so the sooner we are off the better. The question is, what will you do?"

"I have made up my mind to go home with you," said the lady. "Those interlopers must be turned out."

"That's brave of you, but I'm afraid we haven't room."

"We can leave Bola," said Derrick. "He can bang about, and perhaps trace those messengers we heard no more of. And we shall want to know what happens in the town. The Minister of the Interior won't stomach an affront like this. He'll be the laughing-stock of the place. Tell Bola what we have decided, Pedro. Señor Villanova will no doubt send him off as soon as he has definite news."

"I will do my best," said the señor, "but I must act warily. As the President's friend I shall be suspect if the Minister of the Interior has revolutionary designs."

"Then let Bola bring your traps from the house, Aunt," said Derrick. "Also a couple of cushions. We must make you as comfortable as we can. Then we'll be off. Poor Pat is handcuffed, and we can't release him till we get home."

Five minutes later the Gadfly rose once more into the air. Looking through the windows the boys saw a great throng of people streaming across the racecourse. The skirting road was dark with horsemen, bicycles and motor-cars.

"They've had a show after all," said Derrick, with a smile.

CHAPTER THE NINETEENTH - REVOLUTION

IT was still early morning when the Gadfly came within sight of the valley in which lay the Alvarez hacienda. The journey of some six-score miles had taken a little more than half an hour.

There had been a consultation between the boys and Señora Alvarez upon the steps to be taken on their arrival. Pedro was for coming down in the grounds of the hacienda and turning out the gendarmes by main force; but Derrick pointed out that they had only two revolvers among them all.

"But the mine workers will help us," Pedro retorted.

"Let us avoid bloodshed," said the señora. "The gendarmes are after all only innocently doing their duty. No blame attaches to them."

"Indeed, you are in the right of it, ma'am," said Heneky. "And if only I had my hands free—"

"What then?" asked Pedro, as the Irishman paused.

"Why, then I'd ask the lady's permission to take this worm" (he glanced at Mollendo) "and clear the spalpeens out without so much as a shot fired."

"But you would yourself be in danger," said the señora.

"Sorra a bit, ma'am. They're poor harmless creatures, these gendarmes, if you take 'em the right way. But if you frighten them, 'tis after shooting they might be."

There was a general smile, and Señor Gomez, who did not understand English, looked inquiringly from one to another. Pedro explained.

"It is quite true," said Gomez, smiling. "Without doubt Pat is a match for any company of Bolivian gendarmes."

"But it's out of the question," said Pedro. "Stay: let me look at your handcuffs...I think I could knock them off with our pliers if I had more elbow room."

"Then I'll come down behind the hill," said Derrick. "It's just as well not to alarm them by the sight of our machine. I daresay they have heard something about it, and we don't want to be peppered. They can't have seen it yet."

He brought the Gadfly to ground in a hollow of the hills about a quarter-mile from the hacienda. Everybody got out, and a few minutes' work with the pliers released Heneky.

"I'll not keep you waiting long," he said. "Lend me the loan of your revolver, Derrick." He added in Spanish to Mollendo: "Now, you come along with me."

The others watched curiously as the two men walked round the shoulder of the hill.

"Oh dear! I hope Pat is not too self-confident," said the señora. "What does he mean to do?"

She would have been reassured could she have heard how Pat addressed Mollendo when they were out of sight.

"Now, you scoundrel, you'll be hanged sooner or later-probably sooner; or shot, which is the way you intended to serve me. But if you prefer to be shot at once you have only to forget the smallest detail of the lesson I'm going to teach you! Don't slouch; hold yourself up as if you were a man and not the white-livered jackal you are. Look as if you're glad to be alive, though you're precious near dead, I give you my word."

Mollendo walked on meekly, listening in silence as the Irishman laid down his course of action. There was no one in sight in the grounds of the hacienda, and Pat was surprised to hear, from the mine workings beyond, sounds betokening considerable activity.

When they came to the veranda, they saw, through the open French window of the dining-room, Juan breakfasting with the gendarmes. Pat gave Mollendo a significant look. The big man walked into the room, Pat remaining just outside.

"I come to relieve you," Mollendo said. "You are wanted urgently in La Paz, and must march at once."

"But, señor—" Juan began, with a look of wonder.

"There is no time for explanations," said Mollendo hurriedly. He stood exactly two paces from the door, as Pat had bidden him, and he was uneasily conscious of the revolver in the Irishman's hand, knowing well that if he gave the least sign of departing from his orders he would be at the mercy of a dead shot. "The major-domo will provide rations for the journey. See to it, Juan."

The man went away to do his bidding. The gendarmes cleared their plates, donned their caps and took up their rifles, and by the time the major-domo entered with food for their haversacks they were ready to march. A quarter of an hour after Mollendo's arrival they were footing it towards the mountain road. Mollendo and Juan came out on to the veranda together. The half-breed caught sight for the first time of Heneky, and before he could recover from his start of surprise the Irishman had grabbed him and dexterously relieved him of his knife and pistol. Then, taking him by the scruff of the neck, and ordering Mollendo to follow, Heneky pushed him through the room, along a passage, and thrust the two men one after the other into the harness-room. There he locked them up.

The major-domo had watched these proceedings with the liveliest interest and delight.

"What's going on at the mine?" asked Heneky abruptly.

"Diego is back, señor," replied the man. "He has set the men at work."

"He came with that fellow Juan?"

"No, señor. He came just after Señor Pedro had left last night."

"Go round the hill yonder. You will find your mistress there. Tell her that the house is clear of the gendarmes."

When the party from the Gadfly arrived they had learnt from the major-domo how Heneky had disposed of Mollendo and Juan.

"It is all very well, Pat," said the señora; "but I am not at all easy in mind. Such doings are quite illegal. Pray don't think I am ungrateful; but—"

"Believe you me, ma'am, there's no call to be uneasy," said Heneky earnestly. "'Tis the uneasy conscience Miguel Mollendo has, and my old friend José Gomez being alive he hasn't a leg to stand on. And now I'll be after making the acquaintance of your engineer Diego. We haven't yet got to the bottom of Mollendo's pretty plot."

With Gomez and the two boys he set off for the mine. The old workings were deserted, but at the edge of the area devastated by the landslide they came upon Diego superintending the cutting of a new gallery. He started with surprise when he saw his employer's son with three strangers.

"You've come back, then," said Pedro, primed by Heneky.

The man made no reply. He threw an anxious glance in the direction of the hacienda.

"You were expecting Señor Mollendo," Pedro went on. "I'm afraid he is otherwise engaged. I won't ask you to explain your absence; of course it doesn't matter. Your place is filled."

"We'll see about that," muttered the man, moving away.

"Not so fast. Stand where you are. Pat, see what the men are about, will you?"

Heneky went among the labourers, who had ceased plying their picks and shovels. He put a few questions to them, took up and examined some fragments of rock, and returned.

"Sure your fortune's made," he said to Pedro.

"They've struck a mighty fine vein. You'll owe a great deal to the land-slide, I'm thinking. I haven't a doubt this rascal discovered it, and made a very pretty scheme with Mollendo and those ruffians in La Paz to dispossess the lady of her property."

"A pretty scheme indeed," said Pedro. "What shall we do with the fellow?"

"Put him with the others," said Derrick. "We'll get the whole story by and by, and when the President comes back, Aunt Bertha had better see him. It's such bare-faced villainy that I'm sure she'll get justice."

The crestfallen engineer was marched back to the hacienda, and was there locked up with the other prisoners.

The servants had prepared a meal on the veranda, and of the company it was Heneky who showed the keenest appetite for the good food. He had not fared sumptuously in prison. He related how, immediately on his arrival in La Paz, before he could communicate with any of his acquaintances there, he had been arrested on the charge of murder. His trial had been hurried on; Mollendo had testified to the sudden disappearance of Gomez from the camp, and two Indians had sworn to the finding of Gomez's body, stabbed to the heart, in the forest near by.

"But what actually happened to you, Pat, that day you went off by yourself?" asked Derrick.

"The simplest accident in the world," said Heneky, who had already told Gomez the story during the voyage in the Gadfly. "I was after game, as you know, and wandered for hours without having any luck at all. Then I sighted an aguoti, and set off to stalk it, and had just got within shot of the creature when, not having eyes in my feet, I tripped over a root and gave my ankle such a twist that I thought I'd never walk again. I lay all night faint with the pain of it, and 'twas three days before I got back to camp. There were signs of a struggle where José's tent had been, and as I knew he wouldn't have deserted me if he was alive, I believed that Mollendo had done for him and bolted. I searched all about for his body, a pretty useless thing to do in a forest, and spent months making inquiries here, there, and everywhere, for him and Mollendo too, and at last I gave it up, and took to roving on my lonesome again. 'Twas a providence I came upon you two lads, after all these years."

They discussed what course of action should be adopted in regard to the prisoners. It was agreed that nothing could be done until word came from Señor Villanova as to what was happening in La Paz. If his opinion that the country was on the eve of revolution turned out to be correct, it would be unwise to take any steps until the issue between the President and the Minister of the Interior was decided; and in the event of the latter gaining the upper hand, it seemed likely that the mine must be abandoned and the Señora Alvarez must seek safety in flight. Derrick suggested that he should take another trip to La Paz in the Gadfly, and find out at first hand the position of affairs there; but this idea did not commend itself to the rest, and it was decided to await Bola's arrival.

Three days passed. Heneky pushed on the work at the newly-discovered lode, taking occasional trips in the Gadfly with the boys. On the fourth afternoon they all conveyed Señor Gomez back to his home, and in returning, made a circular flight over the mountains. As they wheeled in the direction of the hacienda, and Derrick brought the machine low before making the last ascent, Pedro caught sight of a solitary figure threading its way along the mountain track.

"Come and look, Pat," he said. "Is that man waving a flag to us?"

Heneky went to his side at the window.

"Indeed he is," he said. "A bit of cloth, anyway. I wouldn't wonder but it's Bola."

Derrick manoeuvred the machine until it hovered directly over the man, then let it sink to the ground. Bola tired out after his long march, climbed in at the door. There was a brief conversation between him and his master.

"Boys," said Heneky, "La Paz is in revolution. The Minister of the Interior has proclaimed himself president. There's not a hand raised against him."

"That's bad news," said Derrick. "Aunt Bertha will be upset."

"We shall have a few days' grace," said Pedro.

"The revolutionaries will be too busy to bother about us until they have established the new regime. But then—"

"Why then," said Heneky, "if the worst comes to the worst the lady and all of us can get away in the Gadfly. And sure I'll deal with Mollendo myself first."

Señora Alvarez was greatly distressed when she heard the news. "It's not only for myself," she said. "It will grieve me very much to leave my home, but we have enough to live on in a quiet way in England. But I think of my poor friend the President. He is the best ruler the country has had since the great Bolivar, and it is such a pity that he should be ousted by a scoundrel. I'm afraid they will kill him when he comes back from hunting."

"But won't the army fight for him-some of them, at any rate?" said Derrick.

"They'll never have the chance," said Heneky. "If I know my man, the Minister of the Interior will take care the President never gets back alive. He'll have no warning, you see."

Derrick wore a thoughtful look.

CHAPTER THE TWENTIETH - A PRESIDENTIAL RECEPTION

ABOUT eight o'clock on the following night a dark object, scarcely visible against the stars, circled silently over the house of Señor Villanova on the outskirts of La Paz. Then, having apparently found its bearings, it sank slowly down into the patch of scrub in the rear of the garden. The Gadfly had arrived.

Two figures came quietly out of the machine, and made their way with great caution through the garden towards a lighted window at the side of the house. There was neither blind nor curtain, and the two men, peeping in, saw Señor Villanova reclining in a long chair, with a book in his hand. One of them tapped gently on the glass. Villanova started, laid down his book, opened a drawer of his table and took out a pistol; then quickly switched off the light and approached the window.

"Who is there?" he demanded, lifting the sash an inch.

"Pedro Alvarez."

Villanova threw the window up.

"Come in," he said. "This is a great surprise."

"A secret visit, señor," said Pedro. "And I bring a friend."

The two clambered over the low sill. Villanova closed the window behind them, drew the curtains, and switched on the light.

"The President!" he exclaimed in astonishment.

"Yes, my friend," said the taller of the two visitors, a handsome middle-aged man in hunting dress. "You may well be surprised at my entering in this furtive way. You have dined?"

"An hour ago. But, senor—"

"Let me explain," said the President. "My presence is due to Señor Alvarez and the young Englishman his cousin who traced me to the headwaters of the Manoré river and gave me passage in their wonderful machine. An hour ago I was taking my evening meal in camp three hundred miles away. The news brought by our young friend seemed to show that I ought to be in the city. Well, here I am. Now, will you tell me how matters stand?"

"The city is completely in the hands of the revolutionaries señor. The Minister of the Interior has proclaimed himself President. The army is with him, and though your friends are numerous, in your absence there has been no focus of resistance. Martial law is proclaimed, and no one is allowed to appear in the streets without a permit after nine O'clock.

"So much the better," said the President. "I may count on your assistance?"

"Absolutely, señor. But do I understand that you have come alone?"

"With my two young friends. Is my successor likely to be at home?"

"He is giving a reception at the Palazzo Mlrandola."

"Excellent! At what time does his Excellency receive?"

"At half-past nine."

"Then we have just time. Your wardrobe does not include, I fear, four complete evening suits?"

"You and I are about the same height and build; but the two young men—You have your car? Then I shall be greatly indebted to you if you will fetch two suits, one for Señor Alvarez, the other for his cousin, who, as you know, is rather taller. No doubt you have friends who will oblige us. We cannot count, of course, on a perfect fit, but we must all appear presentable at a presidential reception."

* * * * *

Soon after nine o'clock, when the streets were clear, the Gadfly dropped quietly into the spacious patio of a mansion near the centre of the city. The patio itself was dark and deserted, but the rooms were lighted, and there appeared to be a good deal of movement in the house.

From the door of the machine stepped four men in evening dress, and two men-servants of Señor Villanova's. Bola remained at the door; he had a revolver.

The French windows of the salon were open, and from the dark patio the visitors saw the Minister of the Interior and two of his intimates talking together at the farther end of the room.

"Now, gentlemen," said the President quietly.

He went forward, a little ahead of Señor Villanova and the two boys. At the sound of footsteps in the patio the men turned towards the window. Perhaps they took the advancing figures, dimly seen, for early guests who by some mistake were entering through the patio instead of by the main door, where they would be received and announced by the major-domo. But when the first of the figures came into the light, and with an easy air of nonchalance walked straight into the room, the Minister and his friends stared with a wide-eyed look of amazement. They neither moved nor spoke; it was as though they had suffered a paralytic shock.

"We are a little before the hour, señor," said the President blandly, addressing the Minister, "but I need make no excuses. I understand that during my absence from the city certain-irregularities, let me say, have been permitted, in connection with which your name has been mentioned. You and your associates will please to consider yourself under arrest."

The three men were still speechless. They looked beyond the President at Senor Villanova and the two youths, strangers to them. On either side of the French windows, now closed, stood one of Villanova's servants.

The Minister of the Interior at last found his tongue.

"This is unpardonable," he said, with an attempt at bluster.

"I was not invited, you mean?" said the President. "Naturally." His voice took a sharper note. "I am informed that I should be justified in shooting you where you stand, as a rebel and a traitor. But you shall have an opportunity of explaining your conduct before the courts of your country. At present you are at my disposal. And I warn you to say your prayers before you or your associates show the least sign of resistance, for that moment will be your last."

The conspirators were dumb. It was obvious to the onlookers that they were utterly nonplussed. No doubt they were wondering how the President had got into the city in spite of the guards, how he had contrived so quietly, without disturbance in the streets, to secure the backing which alone could have emboldened him to face his enemies.

"Take them away," said the President. "Search them first."

The baffled plotters made no resistance when Villanova's servants searched them for arms. The French windows were thrown open; escorted by Villanova and the others they were marched out into the patio. Catching sight of the Gadfly they gasped. The Minister of the Interior gave back, but was urged on, and bundled with his friends into the machine. The door was closed upon them, and Bola was ordered to shoot the first of them that attempted to come out.

Villanova and the boys returned to the room. The President was alone. He touched a gong on the table. The major-domo appeared, and stood open-mouthed. "You recognise me?" said the President.

"Your Excellency!" the man stammered.

"Your employer is now a prisoner. You, and all in this house, are accomplices in his treason; your lives are forfeit; but I am willing to believe that you are mere tools in the hands of your superiors. You shall have a chance of redeeming your error. You will carry out the arrangements of this reception exactly as you understood them: receive the guests and announce them. You will not utter a word to show that any change has taken place. You understand?"

"As your Excellency commands," said the trembling man.

Five minutes later there were sounds of arrival.

The door opened.

"His Worship the Mayor," announced the major-domo. "His Excellency the Commandant of the Civil Guard. The Receiver-General of Taxes."

Derrick treasured as a precious memory the expression on the faces of these exalted personages when, entering one after another, they found themselves in the presence of the President. No one could have suspected, from the amiable manner of that gentleman, that there was anything unusual in the occasion; it was quite otherwise with the guests. The first blank look of sheer astonishment was followed in some by craven fear, in others by chagrin, in others by obvious pleasure or relief. They passed behind the President and grouped themselves, exchanging glances, whispering inquiries, subdued even in their surprise and excitement.

The room filled; the tide of arrivals ceased to flow; the major-domo bowed himself out.

"Our numbers are complete, señors," said the President. "Complete, I say, though doubtless you have already noticed that two or three distinguished persons whom you expected to see are absent. They are now State prisoners." There was an audible stir among the company. "They will stand their trial before the appropriate judicial tribunal. As for others who may have committed indiscretions I am disposed, since no harm appears to have resulted, to condone their offences-this once. But I advise them to presume no further on my forbearance.

"I appoint Señor Villanova Minister of the Interior. The state of martial law illegally proclaimed by his predecessor is raised from this moment. Refreshments are provided in the adjoining salon, but I am sure you will excuse me from accompanying you. Gentlemen, I thank you for your attendance, and bid you good-night."

The assembly dispersed, puzzled, curious, in some instances angry, but for the most part relieved. When the last of the guests had disappeared the President turned to the boys.

"Our plans have worked out most admirably," he said. "I cannot sufficiently express my obligations to you. I think I shall have no more trouble here but it will be well to remove those miscreants from the city until I have had time to put affairs in order. Give my compliments to the Señora Alvarez, and my apologies for inflicting the prisoners temporarily upon her. I shall at once institute a searching inquiry into the abominable schemes which have been directed against her property, and against the life of your Irish friend. I will take care that you are formally confirmed in the ownership of the ground upon which you discovered the basis of your wonderful invention, and I shall give myself the pleasure of paying an early visit to the spot."

Taking leave of the President and Señor Villanova the boys returned to the machine. An hour later the discomfited revolutionaries were locked up in an outhouse of the hacienda, and the story of the President's bluff enlivened a cheerful supper-party in the dining-room.

CONCLUSION

THE President was not a man to let the grass grow under his feet. Within a week he had thoroughly reorganised the administration and the revolution was snuffed out like a candle that did not even sputter. Then he sent a troop of cavalry to relieve Señora Alvarez of the custody of the prisoners. They were all conveyed to headquarters; a searching inquiry was made concerning the machinations of the Minister of the Interior and Miguel Mollendo, and in the course of it their plot against the Alvarez estate was laid bare.

It appeared that Diego, the engineer, having discovered a rich lode in the mine, had imparted the discovery to his relative Mollendo, and they had conceived the idea of dispossessing the señora on the ground that the mine had ceased to be worked. Feeling that the arrival of her son and nephew with the new machinery would interfere with their plans, they had bribed Juan the guide to dump the machinery into the river, and to lose the young men in the forest.

It was by a mere accident that Mollendo, when on his way to the hacienda, had met the messenger who was conveying to La Paz the papers and map that were to establish the boys' claim to the cave and the surrounding land. Mollendo had questioned the man, examined his papers, and supposing that a new deposit of minerals had been found, turned back to the city. There the messenger had been thrown into prison, and Mollendo had copied the map and arranged with his friend the Secretary for Mines that the claim should be registered in his name. The unexpected meeting with Heneky at the cave had been a blow to Mollendo, but Heneky had played into his hands by accompanying him to the city, and it had been easy, in collusion with the officials, to get the Irishman convicted on the trumped-up charge of murder. A watch had been kept on the road from the hacienda, and the señora's second messenger had been disposed of in the same way as the first.

At the conclusion of the inquiry the rebel ministers and Mollendo were brought to trial for treason, convicted, and executed. Diego and Juan were sentenced to long terms of imprisonment. Property in the cave was confirmed to Pedro Alvarez, and he and Derrick were decorated with the highest orders of the Republic for their services in bringing the President to the city at the crisis of the revolution.

The performances of the Gadfly were naturally a source of intense curiosity among the Bolivians, and the hacienda became the goal of pilgrimages on the part of some of the citizens of La Paz. These visits became rather embarrassing, and to put a stop to them the boys decided to dismantle the machine, which indeed was showing signs of decrepitude, and to construct another at their leisure, with better materials and after an improved design. They were careful not to give away the secret of their motive power.

When things had settled down, they made an expedition with Heneky to the cave to discover if possible the extent of the crystalline deposit and the cause of the intermittent gush of water through the fissure. After long and patient exploration they found that the water came from the small lake they had noticed in the vicinity of the cave. The lake overflowed after heavy rain, and the overflow found its way through channels, partly underground, in the rocks. The water of the lake was only slightly impregnated with the alkaline substance, and they came to the conclusion that the main source of the "force of levity" lay in the bed of sand in the cave. How long this would last they could not tell; but when they were last heard of they were busily engaged in separating the crystals from the sand and laying in a large stock in readiness for their new machine.

Señora Alvarez pressed Heneky to remain at the hacienda as chief engineer, but he politely declined her offer, and advised her to engage a competent man from England. He had now two competing interests in life: one, the renewal of his old friendship with Señor Gomez; the other, the construction of the second Gadfly.

"I've sailed the sea," he said, "and I've roamed over the face of the earth, but 'deed and all there's no way of roving that can anyway compare with flying through the air. I've had a taste of it, and 'tis the joy of my heart. Sure to the end of my days I'll still be Roving Pat."

THE END

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