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[Illustration: In a flash Nat’s strong arm was about him.—_Page_ 22]


THE MOTOR RANGERS’ CLOUD CRUISER

by

MARVIN WEST

Author of “The Motor Rangers’ Lost Mine,” “The Motor Rangers
Through the Sierras,” “The Motor Rangers on Blue Water,” etc., etc.

With Illustrations by Charles L. Wrenn







New York
Hurst & Company
Publishers


Copyright, 1912,
By
Hurst & Company

-----------------------------------------------------------------------


CONTENTS

      CHAPTER                                                 PAGE
           I. THE MAGNETIC ISLAND                                5
          II. NAT TO THE RESCUE                                 17
         III. THE ISLANDS VANISH                                27
          IV. PROFESSOR GRIGG AND MR. TUBBS                     37
           V. TROUBLE WITH A HAT                                47
          VI. “WHAT WOULD YOU SAY TO A VOYAGE IN THE AIR?”      55
         VII. A STRANGE SAIL APPEARS                            63
        VIII. TRAPPED BY TWO RASCALS                            71
          IX. SOME STRATEGY                                     80
           X. “DING-DONG” AND A GUN                             88
          XI. CAPTAIN LAWLESS TRIES TRICKERY                    99
         XII. “GOOD WORK, MANUELLO!”                           108
        XIII. SOUTH AMERICAN JUSTICE                           120
         XIV. OFF ON THEIR STRANGE VOYAGE                      130
          XV. A SIGNAL THAT MEANT “DANGER”                     140
         XVI. INDIANS?                                         148
        XVII. A QUEER SORT OF GUN                              156
       XVIII. WHAT IT DID                                      166
         XIX. AN INVOLUNTARY PASSENGER                         177
          XX. “ALL OUR LIVES DEPEND ON IT”                     187
         XXI. “FEATHERED AEROPLANES”                           199
        XXII. A SERIOUS ACCIDENT                               211
       XXIII. OVERBOARD!—1950 FEET UP!                         223
        XXIV. THE CITY OF A VANISHED RACE                      231
         XXV. A STRANGE ADVENTURE                              246
        XXVI. SAVED FROM THE SUN GODS                          257
       XXVII. “DID WE DREAM IT ALL?”                           268

------------------------------------------------------------------------




                          THE MOTOR RANGERS’
                              CLOUD CRUISER




                               CHAPTER I.

                          THE MAGNETIC ISLAND.


“What do you make of the weather, Nat?”

Joe Hartley turned to Nat Trevor as he spoke, and scanned the face of
the young leader of the adventure-seeking Motor Rangers with some
anxiety.

But the stout and placid Joe’s unwonted look of apprehension found no
reflection on the firm countenance of Nat Trevor, who stood as steadily
at the wheel of the _Nomad_ as if that sixty-foot, gasolene-driven
craft was not, to use Joe’s phrase of a few moments before, pitching
and tumbling “like a bucking broncho.”

“It does look pretty ugly for a fact, Joe,” rejoined Nat, after he had
scrutinized the horizon on every side.

“And this is a part of the Pacific where we were warned before we left
the Marquesas that we must look out for squalls,” returned Joe, still
looking worried.

“Oh, well, the _Nomad_ has weathered many a good hard blow, not to
mention those waterspouts,” commented Nat. “I guess she’ll last through
whatever is to come.”

At this moment a third boyish countenance was suddenly protruded from a
hatchway leading to the _Nomad’s_ engine-room.

“S-s-s-s-say, y-y-y-you chaps,” sputtered our old acquaintance,
William—otherwise and more frequently Ding-Dong—Bell, “w-w-what’s in
the w-w-w-wind?”

“A bit of a storm, I guess, Ding-Dong,” returned Nat, watching his
steering carefully, so as to send the _Nomad_ sliding easily over the
long, oily swells, “but don’t you mind, old chap. She’ll stand it,
never fear. How are your engines running?”

“L-l-l-like a d-d-d-dollar w-w-watch,” returned Ding-dong, with a note
of pride in his tones.

“Good. Now if only we were farther to seaward of that island yonder,
I’d feel easier,” commented Nat.

“Say, Nat,” struck in Joe, as Ding-dong dived below once more, “it
seems to me we are a long time passing that island.”

“I agree with you, Joe. That is what made me ask Ding-dong about his
engines. At the pace they are turning up, we should have left it behind
us long ago, yet there it is, still on our starboard bow.”

“And we are getting closer in to it all the time, you’ll notice,”
rejoined Joe.

“There must be some powerful currents hereabouts,” said Nat, looking
for the first time a little bit troubled. “There’s something queer
about that island, anyhow. I can’t find it on the chart. According to
that, this part of the mid-south Pacific is absolutely free from
islands or rocks.”

“Hullo,” cried Joe suddenly, “that’s odd! Look, Nat, the island isn’t
really one island at all. It’s two of them.”

This paradoxical speech was really a correct explanation of the case,
as it now appeared. The _Nomad_ had, by this time, made some little
progress over the rising sea, and as the bit of land “opened out,” it
could be seen that there were, as Joe had said, two islands, with a
narrow channel running in between them.

“Phew!” whistled Nat. “This complicates the situation. To make matters
worse——” He stopped short.

“Well?” demanded Joe.

“Never mind,” replied Nat; and then in an undertone he added to
himself: “I may be wrong, but I’ll bet the hole out of a doughnut that
we are being dragged round toward that passage.”

That such was actually the case, he realized to his dismay an instant
later. Head the _Nomad’s_ bow round as he would, some invisible force
still dragged her in toward the two islands. It soon became apparent,
too, that the narrow channel was, in reality, more in the nature of a
cleft between the two masses of land. Its walls were steep and sheer
and formed of grayish rock. It could now be seen that the water in this
abyss was boiling and bubbling as if in a caldron.

Nat and Joe exchanged glances of dismay. It was no longer possible to
disguise the fact that they were momentarily being sucked, as though by
invisible yet resistless forces, toward this ominous looking chasm.

The three youths had set out for the California coast, on which was
their home, some days before, from the Marquesas group of islands,
where they had had some surprising adventures. What these were will be
found set down in the third volume of this series, “_The Motor Rangers
on Blue Water_.” It may be said here, briefly, that their experiences
in the South Seas had included the routing of a rascally band, who had
made a headquarters on one of the Marquesas Group, and the discovering
of the rightful owner of some valuable sapphires which had come into
their possession in a truly remarkable way.

Of how they acquired these sapphires, and of the adventures and perils
through which they passed before they gained full possession, details
will be found in the second volume of the Motor Ranger Series, namely,
“_The Motor Rangers Through the Sierras_.” In that volume, we followed
our youthful and enterprising heroes through the great Sierra range,
and learned of their clever flouting of the schemes of the same band of
rascals whom they re-encountered in the South Seas. Among other feats,
they located and caused the destruction of the hitherto secret fortress
of Colonel Morello, a notorious outlaw. This earned them his undying
enmity, which he was not slow to display. In this volume, too, it was
related how the lads found, in a miner’s abandoned hut, the wonderful
sapphires.

It now remains, only briefly, to sketch the earlier experiences of the
three lads, to give our readers a grasp of their characters. In the
first volume of this series, then, which was called “_The Motor
Rangers’ Lost Mine_,” the three lads set out for Lower California on a
mission which was to involve them in unlooked-for complications.

This errand grew out of Nat’s employment as automobile expert by Mr.
Montagu Pomery, the “Lumber King,” as the papers called him, who made
his winter home at Santa Barbara. Nat, who lived with his mother, was,
at that time, very poor, and much depended on his situation with the
millionaire, in charge of his several cars. But Ed Dayton, who
considered that Nat had superseded him in the place, made trouble for
him. Aided by Donald Pomery, the lumber king’s son, a weak,
unprincipled youth, he hatched up a plot, which, for a time, put Nat
under a cloud. But Mr. Pomery himself proved Nat’s firm friend.

Owing to Mrs. Pomery’s interference, the millionaire was compelled to
discharge Nat, but he almost immediately re-employed him on the
confidential mission of which we have spoken. This was to visit Lower
California and investigate conditions on his timber claims there. Much
rare and valuable wood had been going astray, and Mr. Pomery suspected
his superintendent, Diego Velasco. He lacked proof, however, and Nat he
selected as a bright, trustworthy lad, who could carry out an
investigation painstakingly.

Nat recalled that his dead father had been interested, in his youth, in
a rich mine in Lower California, and the prospect of the trip,
therefore, had a double fascination for him. Mr. Pomery provided an
automobile, equipped in elaborate fashion, for the long trip, much of
which was to be made through desert country. With Mr. Pomery’s
permission, Nat invited his two chums, Joe Hartley, son of a well-to-do
department store keeper, and William Bell, the stammering lad, to
accompany him. The latter’s mother and the former’s father at first
demurred considerably to the trip, but at last they gave their consent.
Nat, for his part, had some trouble winning his mother over. But soon
all was arranged, and they set out. How they discovered the Lost Mine,
and Nat became rich, was all told in that book, together with many
other adventures that befell them. The reader is now in a position to
understand our chief characters, sturdy, intelligent Nat Trevor, with
his curly black hair and dancing blue eyes; stout, red-faced Joe
Hartley, always good-natured, though inclined to be a bit nervous, and
Ding-dong Bell, the cheery, stuttering lad, whose eccentricities of
speech provided much amusement for his companions.

The day on which this story opens was the seventh since their departure
from the Marquesas on their return voyage to the Pacific Coast. They
had left behind them their fellow adventurers, some of whom wished to
return by steamer, while others were anxious to continue their travels
in the fascinating South Seas. So far, smiling skies and sunny seas had
been encountered. But this particular day had dawned with a smoky, red
horizon, through which the rising sun blazed like a red-hot copper ball.

It had been oppressively hot—torrid, in fact. But although the air was
motionless and heavy, the sea was far from being calm. It heaved with a
swell that tossed the _Nomad_ almost on her beam-ends at times. That
some peculiar kind of tropical storm, or typhoon, was approaching, Nat
felt small doubt. A glance at the barometer showed that that instrument
had fallen with incredible rapidity. A candle, held in the thick, murky
air, would have flamed straight skyward without a flicker.

Dinner was eaten without a change being observable in the weather
conditions, and, on coming on deck to relieve Joe at the wheel while he
went below to eat, Nat sighted the bit of land toward which they were
now being drawn like a needle to a lodestone. In the meantime the
weather had been growing more and more extraordinary. The copperish sky
had deepened in color till a panoply of angry purple overspread the
heaving sea. The sun glared weakly through the cloud curtains as
through a fog. But still there had come no wind.

Hardly had the two lads on the bridge of the _Nomad_ realized that they
were inexorably being drawn toward the two islands, however, when from
far off to the southwest there came a low, moaning sound. It seemed
almost animal in character; like the lowing of an angry bull, in fact,
was the comparison that occurred to Nat. The sound increased in
violence momentarily, while the sky from purple changed to black, and a
blast like that from an open oven door fanned their faces. Through this
awe-inspiring twilight the _Nomad_ continued her inexplicable advance
toward the two islands.

“Here it comes!” shouted Joe suddenly, as, from the same quarter as
that from which the wind had proceeded, there came a sudden, angry roar.

“Hold tight for your life!” flung back Nat over his shoulder, gripping
his steering wheel with every ounce of strength he possessed.

And thus began hours of stress and turmoil, which the Motor Rangers
were ever to remember as one of the most soul-racking experiences of
their young lives.




                              CHAPTER II.

                           NAT TO THE RESCUE.


“Wow! This is the worst ever!”

Joe was clinging tightly to the bridge of the _Nomad_.

Spray, flying like dust through the dense mid-afternoon twilight, stung
his face. The wind whipped out his garments stiff, as if they had been
made of metal, and half choked the words back down his throat.

Nat made no reply. He clung grimly to his wheel, striving with might
and main to head the _Nomad_ into the furious waves. Ding-dong Bell had
emerged on deck an instant before, but had been promptly ordered below
again.

“Keep your engines doused with oil; give them plenty of gasolene, and
stand by for signals,” had been the young captain’s orders.

Below, beside his shining, laboring engines, Ding-dong was valorously
striving to carry those orders out. But the strain on the motors was as
great as they had ever been called upon to bear, even in the memorable
encounter with the waterspouts.

Besides heading into the storm, Nat was “bucking” the strange current
that set toward the island chasm. But powerfully as the _Nomad’s_
propeller churned the driving seas, the unseen tide was more powerful
still.

“Nat, we’re bound to be drawn into that gorge within a few minutes,
unless——”

“Unless a miracle happens.”

Joe’s comment and Nat’s rejoinder were both shouted above the storm.
Their voices sounded feeble as whispers amid the fury of the
conflicting elements.

Hardly a hundred yards now separated the storm-battered _Nomad_ from
the towering walls and boiling waters of the chasm. Inevitably, unless
the miracle of which Nat had spoken occurred, they must, in a few
moments, be laboring in the midst of that ominous-looking place. While
the thought was still pulsating through their minds, and their hearts
beat high with apprehension, the dreaded thing happened.

The _Nomad_ was suddenly caught, as if by hands bent on causing her
dissolution, and hurtled straight into the cleft between the islands.
Nat, hardly conscious of what he was about, directed her course so that
the craft was not instantaneously dashed to bits against the side of
the cliffs. Joe, too alarmed to utter a word, simply clung tight to the
rail. Below, in the engine-room, Ding-dong Bell was thrown from his
feet and smashed up against a steel stanchion.

The blow knocked him senseless. And so, with her engineer unconscious,
another member of her crew almost useless from fright, and only one
guiding spirit on board her, the _Nomad_ hastened forward into what
seemed certain annihilation.

Within the cleft it was black as night. The angry seas that boiled and
gnashed between the steep walls, for an instant completely hid the
_Nomad_ from view. But presently she gallantly emerged, fighting like a
live thing for her life.

The wind, compressed within those narrow confines, blew with a force
and fury almost incredible except to those who have passed through a
South Pacific storm. It would have been impossible to cry out and make
one’s voice heard. The most powerful shout would not have been audible
a foot away. The situation of the Motor Rangers appeared to be almost
desperate.

“Can she last out? Can she possibly stand this terrific battering?”

Such were the thoughts that galloped through Nat’s excited brain. He
rang the electric signal for “more power,” but no response came from
the engine-room, where Ding-dong lay senseless beside his motors.

Then he turned about to look for Joe. Now that his eyes had grown used
to the darkness it was possible to see—as one sees on a night when the
moon is obscured by heavy clouds. The young captain’s heart leaped into
his mouth as his eyes pierced the obscurity.

Except for himself, the bridge was empty of life.

Joe Hartley had vanished!

“Swept overboard!” shot through Nat’s brain.

At the same instant he caught a cry:

“Help! Help!”

It appeared to come from far astern.

“Joe!” shouted Nat into the darkness.

“Help!” came the cry again. It was closer this time.

A coil of light but strong rope was looped to the bridge in front of
Nat. Without an instant’s hesitation, he tied one end of it about his
waist. He had reached a desperate determination. If he got a chance, he
had made up his mind to save Joe Hartley if it were humanly possible.
The other end of the coil he knew was made fast to the bridge rail, so
that a final testing of the knot about his waist was all that was
necessary to put his daring scheme into execution. But first Nat fixed
the wheel by means of the metal grips provided for that purpose.

Then, with every nerve a-quiver, every muscle flexed, he waited for
another summons. Suddenly it came.

“Help, Nat! I——”

A smother of foam swept glimmering past the Nomad. It was luminous with
phosphorescence. Amidst the greenish, ghastly glare, was plainly
perceptible a darker spot. It was a human head.

“Hold on, Joe! I’ll be with you!” shouted Nat, and then, without
hesitation, he mounted the bridge rail at the port side and plunged
into the mass of spume.

Fortunately for those interested in the adventures of the Motor
Rangers, at that instant a freak of the current spun Joe’s body about
and flung him, like a bit of driftwood, toward the side of the _Nomad_.
In a flash Nat’s strong arm was about him. It was just in time, too,
for Joe, who had been swept from the bridge unseen when the _Nomad_
encountered the angry maze of cross currents and tide rips, was almost
exhausted.

In this condition he was not in full possession of his ordinary
presence of mind. He clung to Nat desperately, with a grip that
threatened to pull both rescuer and rescued under water together.

Nat, battling with the sharp, angry waves, as choppy and angular as
giant fangs, had all he could do without struggling with Joe. Again and
again he tried to break the other’s grip, but without avail. The hold
of a drowning man or boy is the most tenacious known. It is almost
impossible to loosen it.

“Joe, you must let go of me!” gasped out Nat.

But Joe only clung in a more leech-like fashion. What with the other
lad’s dead weight clinging to him, and the conditions against which he
was laboring, Nat, strong as he was, felt his strength being rapidly
sapped.

Luckily, so intense had been the heat, the lads wore only light
tropical trousers and sleeveless undershirts. Had they been incumbered
with ordinary clothes, they could not have survived a quarter of the
time that Nat and Joe did.

Nat began hauling in on his line, but with Joe gripping him so tightly,
it was too much of a task.

“Joe, I hate to do it,” he said at length, “but I must, old fellow, I
must!”

With these words, Nat did what he would have done with anybody else
when first he realized the conditions. He struck Joe a blow on the head
that completely robbed him of his senses. The lad’s vise-like grip
relaxed. Under these circumstances, Nat could handle him easily.

By strong, rapid, over-hand motions, he hauled himself and his burden
closer and closer to the side of the _Nomad_. At last they reached it.
And now came the most difficult part of Nat’s enterprise. He had to get
back on board, and, more than that, to get Joe there, too.

The _Nomad_ was rolling and plunging till she was almost rail under at
every roll. A sudden lurch of extra violence gave Nat his opportunity.
It brought the bridge rail within reach of his free hand. He grasped it
with a tenacious grip. But the next instant he was almost flung back
into the sea again, as the little craft righted, and the lad, with his
unconscious burden, was carried high above the boiling waters.

But Nat’s muscles had been trained to nickel steel suppleness and
strength. He managed to hold on somehow, and the next roll to port of
the _Nomad_ gave him an opportunity to get one foot on the edge of the
bridge. Thus he clung till the next wild roll in the opposite direction
was over.

Then exerting a reserve force he had never before had occasion to bring
into play, the young captain drew up Joe’s limp form and bundled it
bodily within the bridge railings. This done, he clambered over
himself. But he felt queer and dizzy. He could hardly keep his feet,
even though he hung on to the rail. His head spun like a teetotum.

“I—why, what’s the matter with me? I—I believe I’m going to——”

Nat did not conclude his sentence in words. Instead, he enacted it by
giving a crazy plunge backward and collapsing in a heap, almost
alongside the unconscious Joe.




                              CHAPTER III.

                          THE ISLANDS VANISH.


Nat sat upright with a strange singing sound in his ears. It was
insufferably hot. He fairly panted as he opened his eyes. The sweat ran
off him in rivulets. For an instant recollection paused, and then
rushed back in an overwhelming flood.

“We were in that channel between those two queer islands,” mused Nat;
“and we—gracious, where are the islands?”

He had staggered dizzily to his feet and was looking about him. He knew
he could not have lain senseless very long, for his garments were still
wet, despite the intense heat. But the islands were nowhere to be seen.

It was still partially dark, a murky twilight replacing the former
deeper blackness. But an indefinable change had taken place, somehow,
in the atmosphere. Nat drew in his breath with difficulty. It seemed to
scorch his lungs.

He glanced over the side of the craft and then drew back with an
alarmed cry. The water all about them was bubbling and eddying
furiously. A shower of spray from one of the miniature waterspouts
struck Nat in the face. It was this that caused his exclamation and
made him step back hastily, just as if, in fact, he had been struck a
blow in the face.

The water was boiling hot!

Where it had spattered on the lad’s skin it had instantly raised
blisters.

“Well, we certainly have landed in a surprising sort of fix this time,”
muttered Nat to himself.

He bent over Joe. The lad had not yet regained his senses. But he was
breathing heavily, and this stilled a dreaded fear, which, for a moment
had almost caused Nat’s heart to stop beating.

“This air is suffocating,” gasped Nat presently. “It smells like it
does when they are fumigating a room.”

He ran his tongue around his dry mouth in an effort to moisten it, for
it felt parched and cracked. The reek of sulphur in the air, too,
caused his throat to contract and his nose and eyes to tingle
unmercifully.

But this stench also told Nat something. It furnished him with a
partial explanation of the extraordinary occurrences that, as it
seemed, were not yet over.

“This whole disturbance is volcanic,” reasoned the boy. “That is the
cause of this awful sulphur smell. But that doesn’t account altogether
for the sudden disappearance of those islands. I wonder——” But here he
broke off his meditations.

Joe was plainly in need of immediate attention, and Nat devoted his
efforts to trying to raise the recumbent lad. He wanted to get him
below to the cabin, where there was a well-stocked medicine chest and a
supply of reasonably cool water.

But, weakened as he was, Nat couldn’t accomplish the task.

“What’s the matter with me, anyhow?” he asked himself half angrily.
“This sulphur stuff must have knocked all my senses out of my head.
Where’s Ding-dong, I wonder?”

He rang the engine-room call sharply. But there was no response. No
Ding-dong appeared.

“Maybe the signal is out of whack,” muttered Nat, who had noticed some
time before that the engine had stopped running. “Guess I’ll go below
and see what’s the matter.”

It was the work of an instant to reach the hatchway leading below, and
dive into the engine room. What met Nat’s eyes there made him jump
almost as violently as he had when the boiling water struck him.

“Great Scott!” he exclaimed, as his gaze fell on the unconscious
engineer, “if this isn’t worse and more of it. Poor Ding-dong is
knocked out, too; cut on the head. It doesn’t seem to be a bad gash,
but it has deprived him of his senses. Well, if this isn’t a fine
kettle of fish! In the midst of a boiling sea with two unconscious
chaps on my hands!”

Ding-dong stirred and moved uneasily as Nat examined his wound.

“Let me be!” he muttered peevishly; “lemme be.”

“That’s just what I’m not going to do,” rejoined Nat cheerfully.

On the wall of the engine room was a tap leading from the drinking
water tanks of the craft. Nat saturated his handkerchief under this
faucet and bathed Ding-dong’s wound. Then he applied the water
plentifully to the lad’s face, and, opening his shirt, doused him with
it.

Under this treatment, the unconscious lad sat up and opened his eyes.

“Hullo, Nat!” he exclaimed, like one awakening from a long sleep.
“What’s up? What on earth has happened? Where are we? What makes it so
hot?”

As usual, under strong excitement, Ding-dong forgot to stutter, as Joe
termed it.

“I can only answer two of your questions,” replied Nat. “‘What’s up’ is
that poor Joe is lying senseless on the bridge. He was washed overboard
in that chasm. You’ve got to try to help me get him to the cabin. ‘What
on earth has happened,’ is this: We have, apparently, passed through
the chasm, and the islands have vanished in some mysterious fashion,
although we can’t be far from where they were. The sea all about us is
boiling hot, and I guess we are in the very core of some strange
volcanic disturbance or other.”

“Cc-c-c-crickets!” sputtered Ding-dong, rising dizzily but pluckily to
his feet, “we do seem to run into some mighty queer adventures, don’t
we? Come on. I’ll give you a hand with poor old Joe. But, by the way,
what have you been doing all this time?”

“Oh, I-I-guess I went to sleep for a while, too,” responded Nat, rather
confusedly, and without mentioning his heroic rescue of Joe from the
waters of the rift.

He was spared answering further questions, for it required their united
strength to carry Joe to the cabin. Ordinarily, this would not have
been so, but the heat was so terrific that it had sapped the strength
of both boys till they had but half of their accustomed energy and vim.

Joe was laid on a locker and restoratives applied. Presently he was
able to sit up, and then out came the story of Nat’s rescue. The lad
colored brilliantly as Joe and Ding-dong both poured out their praise
unstintedly.

“But, say,” exclaimed Joe, rubbing his head and looking suddenly
bewildered, “I’ve got an awful bump here. I guess I must have hit my
head before your brave——”

“I hit it for you to keep you quiet,” burst out Nat; “and if you don’t
shut up now, I’ll bust it again.”

Going on deck, the three lads found that it had grown lighter. But the
water still boiled about them furiously. Clouds of sulphurous steam
arose from it, making them cough and choke.

In the brighter light they had quite an extensive view of their
surroundings. But, of the islands, not a trace appeared. They had
vanished as if they had been the fabric of a dream.

“By George! I have it!” cried Joe suddenly. “Those islands were of
volcanic origin. Didn’t you notice how bare and bleak they were? I’ll
bet that in this disturbance, whatever it is, they have subsided as
suddenly as they arose.”

“Such cases are not uncommon,” rejoined Nat. “Only last year, Captain
Rose, of the missionary schooner _Galilee_, of San Francisco, reported
seeing an island of some extent arise and then vanish again before his
very eyes.”

“W-w-w-well,” sputtered Ding-dong, with a grin and a return to his old
manner, “w-w-w-we can r-r-r-report the same thing; but as t-t-this
isn’t a go-go-gospel schooner maybe nobody w-w-w-will believe us.”

“My suggestion is, that we get the engines going and get out of this
without delay,” said Nat.

“Here, too,” agreed Joe Hartley. “There’s nothing to hang about here
for.”

An examination of the engines showed that, in falling, Ding-dong had
shut off the gasolene supply valve, and had thus stopped the motors.
This was soon remedied and the motors set going again. As the _Nomad_
cut her way through the boiling sea where lately the twin islands had
stood, they all felt like raising a fervent prayer of thanks to
Providence for their wonderful deliverance.

“I’ve often heard of such things on the Pacific, but I never expected
to live through one,” was Nat’s comment.

“Nor I,” was Joe’s rejoinder; “and I don’t know that I should care to
repeat the experience. But hullo!” he broke off suddenly, “what’s that?
No, not over there; off this way!”

He pointed excitedly to a small black object, which, in the now clear
atmosphere, was visible at the distance of about a mile to the
southeast of them.

“It’s a boat,” announced Nat, after a brief scrutiny of the strange
object.




                              CHAPTER IV.

                     PROFESSOR GRIGG AND MR. TUBBS.


“So it is. What on earth can it be doing out here? Wait a jiffy, I’ll
go below and get the glasses.”

Joe, now fully recovered, dived into the after cabin and soon
reappeared with a pair of powerful binoculars.

Nat focused them on the distant object, which, by this time, was
visible, even to the naked eye, and reported it to be a small boat,
painted white, and looking like a ship’s dinghy, or small lifeboat.

Excitement ran high on board the _Nomad_ when Nat proclaimed that he
was almost certain he had seen an arm wave from the small craft.

“I couldn’t be quite sure, though,” he admitted. “Here, Joe, you take a
look.”

The chubby-faced Joe now bent the glasses on the object of their
scrutiny.

He gazed intently for a minute, and then uttered a shout.

“By ginger, Nat, you’re right!” he exclaimed. “There _is_ someone on
board. There must be something the matter with them, though, for they
seem to be collapsed in a kind of bundle on the thwarts.”

“We must make all speed to their aid,” said Nat, signaling for more
power. “Poor fellows, if they have been adrift in all that flare-up,
they must be about dead.”

“I should say so,” agreed Joe.

As they neared the boat, Nat began blowing long blasts on the electric
whistle, to let the occupants know that aid was at hand. In response, a
figure upreared itself in the drifting craft, waved feebly once or
twice, and then subsided in a limp-looking heap.

“I reckon we’re only just about in time,” said Nat grimly, coaxing
another knot out of the _Nomad_.

As they drew alongside the boat, they saw that not one but two persons
occupied it. The one who had signaled them from a distance proved to be
a short, stocky little man, with a crop of brilliant red hair and a
pair of twinkling blue eyes. The merry flash in those optics had not
been dulled, even by the terrible ordeal through which, it was
apparent, he and his companion had passed.

“Hullo, shipmates! Glad to see you!” he chirruped, grinning up at the
boys on the bridge with a look of intense good humor.

His white duck clothes were scorched, and his rubicund hair, on close
inspection, proved to be singed, but nothing appeared capable of
downing his amiability.

His companion was of a different character entirely. He was dressed in
duck trousers and black alpaca coat. White canvas shoes adorned his
extremely large feet. But it was his face that attracted the boys’
attention. It was large, round and learned looking, with a thin-lipped
mouth cutting the lower part of it like a gash. Above this, a huge,
bony nose protruded, across which was perched a pair of big,
horn-rimmed spectacles. A crop of sparse gray locks crowned his high
forehead and was scattered sparingly over his large, but well-shaped
head, which was bare.

“God bless my soul, George Washington Tubbs, but I’ve lost my hat
again!” he exclaimed to his companion, as the _Nomad_ drew alongside.

“We’d have lost more than that, I fancy, if it hadn’t been for this
here craft,” observed George Washington Tubbs, with a wink at the boys.
“We’d have been a pair of buckwheat cakes, well browned, professor,
when they found us.”

“I wish I could find my hat,” muttered the spectacled individual in a
contemplative tone, peering about under the seats.

“It was blown off when the island busted up,” rejoined Mr. Tubbs. “But
we’re keeping these gentlemen waiting. I presume,” he went on,
addressing the boys, “that it is your intention to rescue us?”

Nat could hardly keep from laughing. His first impression was that they
had encountered a pair of harmless lunatics. But something in the
manner of both men precluded this idea almost as soon as it was formed.

“Won’t you come aboard?” he said politely.

It seemed as inadequate a remark as Stanley’s famous one to Livingston
in the wilds of Africa; but, for the life of him, Nat couldn’t have
found other words.

“Thanks; yes, we will,” responded Mr. Tubbs, with decisive briskness.
“Oh, by the way! Don’t move! Don’t stir! Just as you are, till I tell
you!”

Nat’s suspicions of lunacy began to revive.

Mr. Tubbs bent swiftly, and picked up what looked like a large camera
from the bottom of the boat. Only it was unlike any camera the boys had
ever seen. It was a varnished wooden box, with a big handle at the
side. Mr. Tubbs gravely set it up on its tripod and began turning the
handle rapidly.

“Now, you can move about! Let’s get action now!” he shouted, waving his
free hand.

“This will be a dandy film!” he continued, addressing the world at
large. “Gallant rescue of Professor Thaddeus Grigg and an obscure
individual named Tubbs, following the disappearance of the volcanic
isles.”

In good-natured acquiescence to Mr. Tubbs’ orders, the boys began
bustling about. Ding-dong Bell, who had come on deck when he got the
signal to stop his engines, was particularly active.

“Now, then, professor,” admonished Mr. Tubbs, “up with you.”

“Without my hat?” moaned the professor; but he nevertheless clambered
over the side of the _Nomad_, the boys helping him, while Mr. Tubbs
kept up a running fire of directions.

“Keep in the picture, please. Look around now, professor. Fine! Good!
Great!”

These last exclamations came like a series of pistol shots, and
seemingly proclaimed that the speaker was well satisfied with the
pictures he had made. The professor being on board, Mr. Tubbs followed
him, the boys helping him up with his machine, and with a box which, so
he informed them, contained extra films.

Professor Grigg, as the red-headed, moving-picture man had called him,
was too much exhausted to remain on deck, but retired to the cabin
escorted by Ding-dong. As he went he was still murmuring lamentations
over his hat.

“It’s his weakness,” explained Mr. Tubbs, who seemed to be in no wise
the worse for his experience, “he’s lost ten hats since we left ’Frisco
in the _Tropic Bird_.”

The name instantly recalled to Nat an item he had read in the papers
some months before, concerning the setting forth on a mysterious
expedition of Professor Grigg of the Smithsonian Institute and one
George Washington Tubbs, a moving-picture photographer of some fame.
The object of the expedition had been kept a secret, and the
newspapermen could elicit no information concerning it. It had been
rumored, however, that its purpose was to record the volcanic phenomena
of the South Pacific.

“Is—is that _the_ Professor Grigg?” asked Nat, in rather an awestruck
tone.

“It is,” responded Mr. Tubbs, “and this is _the_ Mr. Tubbs. I’ve taken
moving pictures of the Russo-Japanese war, of the coronation, of the
Delhi Durbar, of the fleet on battle practice, of—of everything, in
fact. I’ve been up in balloons, down in submarines, sat on the
cowcatchers of locomotives, in the seats of racing automobiles, hung by
my eyebrows from the steel work of new skyscrapers; but I’ll be
jiggered if this isn’t the first time I ever took a moving picture of
an island being swallowed up alive—oh, just like you’d swallow an
oyster.”

“Then the island was swallowed?” asked Joe, with wide-open eyes.

“Swallowed? I should say so. And with a dose of boiling water, too. But
I got my pictures! I got my pictures!” concluded Mr. Tubbs triumphantly.

“But where’s your schooner? How did you come to be drifting about in an
open boat?” inquired Nat.

“Ah, as Mr. Kipling says, ‘that’s another story,’” said Mr. Tubbs. “I
guess I’ll have to leave that part of it to the professor. But—hullo,
here he comes now. I guess he’s feeling better already. Possibly he’ll
tell you the story for himself.”

“I shall be very glad to,” said the professor, who, after partaking of
some stimulants from the _Nomad’s_ medicine chest, already felt, as he
said, “much revived.”

“You see in us, young men,” he continued, “the sole members of the
volcanic phenomena expedition of the Smithsonian Institute and the
British Royal Geographical Society, who adhered to the duty before
them. Would you care to hear how we came to be adrift as you found us?”

“Would we?” came in concert from the boys.

“Then I——” began the professor, and then broke off and felt his bare
head. “Can—can any one lend me a hat?” he asked.




                               CHAPTER V.

                          TROUBLE WITH A HAT.


He was speedily furnished with a peaked yachting cap belonging to Nat.
It sat oddly, almost comically, on his large head, but none of the boys
was inclined to laugh at the professor just then. They were far too
interested in hearing what the eccentric man had to tell about the
voyage of the _Tropic Bird_.

“We sailed from San Francisco, as you no doubt know from the papers,”
said the professor, “without the object of our mission being divulged.
There is no harm in telling it now.

“It had been ascertained that a certain phase of the sun spots would be
reached on this present day. As you are perhaps aware, it has long been
a theory of scientific men that there was some intimate relation
between that phenomenon and the volcanic disturbances and earthquakes
that occur in these seas from time to time.”

“I think that we learned something like that in physics,” said Nat,
nodding.

“In physic?” chuckled Joe, but was frowned down.

The professor went on:

“It was my duty, assigned to me by the Smithsonian Institute and the
British Royal Geographical Society, working in concert, to investigate
such a disturbance and make elaborate reports thereon. At my
suggestion, it was also decided to engage a moving-picture operator to
take photos of the whole scene, which must prove of inestimable benefit
to scientific knowledge. The _Tropic Bird_ was chartered to convey the
expedition, and Mr. Tubbs was placed under contract to take the
pictorial record of the scene, if we were fortunate enough to encounter
one.

“We cruised about for some time, awaiting the exact condition of the
sun spots which would indicate that a phenomenon of the kind I was in
search of was about to be demonstrated. Some days ago my observations
showed me that the desired condition was at hand. As fortune would have
it, on that very day we sighted these islands—or rather those islands,
for they have completely vanished as I predicted they would.

“We landed, and found the islands to be of distinctly volcanic origin,
and, seemingly, of recent formation. At any rate, they are not charted.”

Nat nodded.

“Of course there was no trace of habitation. But a few creepers and
shrubs of rapid growth had taken root in the clefts of the lava-like
rock, of which the islands were composed. I saw at once that it was
here, if anywhere, that a seismic disturbance would result, in all
probability, providing the conditions were favorable. That night, on
our return to the ship, the captain of it waited on me.

“After much beating about the bush, he informed me that his crew was
aware of my belief that the islands would be the center of a volcanic
disturbance, and that they refused to remain in the vicinity. He denied
being alarmed himself, however. I succeeded in calming the crew’s
fears, and we remained at anchor off the islands for some days. At
last, signs of the storm which broke to-day began to make themselves
manifest on my instruments. I realized that the great moment was at
hand.

“I warned Mr. Tubbs, here—a most valuable assistant—to be ready at any
moment. I was confident that with the breaking of the storm the islands
would vanish. But nothing was said to the crew. Quite early to-day Mr.
Tubbs and I embarked in that small boat and lay off the islands. I was
certain that the storm would be magnetic in character, and would break
with great fury.”

“However did your boat live through it?” asked Nat.

“She is fitted with air chambers, and specially built to weather any
storm,” was the reply. “But to resume: The cowardly captain, when he
saw the storm coming up, sounded a signal for us to return on board.
When we did not, he hoisted sail and made off, leaving us to our fate.
The storm broke, and there was a spectacle of appalling magnificence.
Mr. Tubbs behaved with the greatest heroism throughout.”

Here Mr. Tubbs blushed as red as his own hair, and waved a deprecatory
hand.

“I guess it was watching you kept me from feeling scared,” he declared,
addressing the professor; “but anyhow, I got my pictures.”

“We have some faint idea of what the storm was,” put in Nat; “but can
you explain something to us?” and he described to the professor the
manner in which the _Nomad_ had been drawn toward the volcanic islands.

“Pure magnetism,” declared the scientist, “a common feature of such
storms.”

“But our craft is of wood,” declared Nat.

“Yes, but your engines, being metallic, of course, overcame that
resistance. You are fortunate, indeed, not to have been drawn down when
the islands vanished. It was a terrific sight.”

Nat explained that during that period they were all unconscious and
then went on to tell of the experiences through which they had passed.

“Oh, why wasn’t I on board your craft?” moaned Mr. Tubbs, as he
concluded. “What a picture that chasm would have made! It’s the
opportunity of a lifetime gone.”

The boys could hardly keep from smiling over his enthusiasm; but Nat
struck in with:

“It’s an opportunity I don’t want to encounter again,” an opinion with
which everybody but Mr. Tubbs—even the professor—concurred.

“And now,” said the man of science suddenly, “I don’t wish to alarm
you, young men, but it is possible that there may be some reflex action
exerted by this storm. In other words, there may be a mild recurrence
of it. In my opinion we had better get as far away from this spot as
possible.”

The others agreed with him. Ding-dong dived below to his engines. Nat
took his station on the bridge.

“By the way, what about the boat?” asked Nat suddenly, referring to the
craft from which they had rescued the scientist and his assistant.

“Unless you want it, we will let it drift,” said the professor. “It is
too large for you to hoist conveniently, and it would impede your speed
if you towed it.”

And so it was arranged to leave the boat behind, but Mr. Tubbs took a
series of pictures of it as the _Nomad_ sped away. The professor also
waved the craft, in which they had weathered so much, a farewell. But,
when doing so, in some manner the peak of his borrowed cap slipped from
between his fingers. The headpiece went whirling overboard, and fell
into the sea with a splash.

“God bless my soul, I’ve lost my hat!” he exclaimed for the second time
that day, as the catastrophe happened.

“He’ll use up every hat on board. You see if he don’t,” confided Mr.
Tubbs to Nat, while the professor gazed fondly at the spot where the
cap had vanished.




                              CHAPTER VI.

              “WHAT WOULD YOU SAY TO A VOYAGE IN THE AIR?”


After breakfast the next morning, the professor appeared on the bridge
with Nat when the latter took his daily observation, a practice which
was, of course, in addition to the regular “shooting the sun,” which
took place at noon. The man of science had already made a deep
impression on the lad. He was eccentric to a degree; but in common with
many men of ability, this was a characteristic that in no way appeared
to affect his scientific ability. The evening before he had entertained
all hands with fascinating tales of his experiences in various parts of
the world. Already everybody felt the same respect for Professor Grigg
as was manifest in the manner of the irrepressible Tubbs.

Nat operated his instruments and then noted the result on a pad, to be
entered later in the log book. The professor peered over his shoulder
as he jotted down his figures.

“Pardon me,” he observed, “but you are a hundredth part of a degree out
of the way on that last observation.”

For an instant Nat felt nettled. He colored up and faced round on the
scientist. But Professor Grigg’s bland look disarmed him.

“Is that so, professor?” he asked. “How is that?”

“Let me test your instruments,” was the reply. “It is impossible to
tell without that.”

Nat handed the various instruments over to his learned companion. The
professor scrutinized them narrowly.

“I think,” he said finally, “that the magnetic influences of
yesterday’s storm have deflected all of them.”

“Of course,” agreed Nat. “How stupid of me not to have thought of that!
Is it possible to adjust them?”

“I will try to do so,” said Professor Grigg, and, placing a sextant to
his eye, he began twisting and adjusting a small set screw.

Several times he lowered the instrument, and, taking out a fountain pen
and a loose-leaf notebook, wrote down his readings. Nat watched him
with some fascination. There is always a pleasure to a clever lad in
watching a man doing something which he is perfectly competent to do.
The professor, the instant he laid his hands on the instruments,
impressed Nat as possessing the latter quality to a degree.

“Just as I thought,” said the professor finally, “your instruments have
been deflected. But we will set them right at noon. A few simple
adjustments, that is all. But I find that you have kept them in
wonderful shape, considering your rough and trying experiences.”

“We have always tried to,” said Nat. “We knew how much depended on
them.”

“And yet,” mused the professor, with his eyes fixed intently on Nat, as
the lad stood at the wheel, “without the ability to understand them,
those instruments would be worthless. Conradini, the Italian explorer,
learned that.”

“At the expense of his life,” put in Nat. “The lesson was lost.”

“Ah, you have heard of Conradini?” asked the professor, in seeming
surprise.

“I have read of him in that pamphlet on aerial exploration issued by
the Italian Royal Society,” was the reply.

The professor readjusted his glasses. In his astonishment, he almost
lost his latest piece of headgear—loaned him by Ding-dong. It was a not
too reputable-looking Scotch tam o’shanter.

“You have a knowledge that surprises me in one so young,” he declared
at last. “You take an interest in exploration, then?”

“That was the object of the Motor Rangers, when first we founded them,”
declared Nat. “I think,” he added, with a twinkle in his eye, “that
we’ve had our fair share of adventure.”

“From what you have told me of your enterprises, I agree with you,”
assented the professor warmly. “But you have not told me yet of the
future.”

“How do you mean?” asked Nat.

“I mean, what plans have you ahead of you? What do you intend to do
next?”

The question came bluntly. Nat answered it with equal frankness.

“I really don’t know,” he said. “As you are aware, though, our course
is now laid for Santa Barbara.”

“So you said last night, when you kindly offered us a passage home,”
said the professor.

He paused for an instant, and Nat swung the _Nomad’s_ bow around a
trifle more to the south.

“Have you no plans for further adventurous cruises or auto trips?”
pursued the man of science.

Nat laughed.

“I guess we’ve had our fill of adventure for a time,” he said; “that
cleft between the volcanic islands nearly proved our Waterloo.”

“Nonsense; such lads as you could not live without adventure,”
admonished the professor, making a frantic grab at his hat, as a
vagrant wind gave it a puff that set it rakishly sidewise above one
ear. “Do you mean to say that you feel like settling down to humdrum
life now, after all you have seen and endured?”

“I guess we all feel like taking a rest,” said Nat. “We have had a
fairly strenuous time of it lately.”

“Granted. But it has put you into condition to weather further times of
stress and trial. Ever since we had that talk last night about the
Motor Rangers, and what they have accomplished, it has been in my mind
to broach a proposition to you.”

“To us?” temporized Nat. “I don’t see where we could be of any use to
Professor Thaddeus Grigg, the most noted scientist of investigation of
this age.”

The professor raised a deprecatory hand.

“As if you had not been of the highest service to me and to my
companion already,” he exclaimed. “Had it not been for you, we might
have—oh, well, let us not talk about it. That coward of a captain——”

He broke off abruptly. Nat waited for him to resume speaking.

“What I wanted to approach you about was this,” resumed the professor,
after a minute. “From the moment I met you, you appeared to me to be
self-reliant, enterprising boys, who mixed coolness and common sense
with courage. Such being the case, you are just the combination I have
been seeking for, to carry out a project which awaits me on my return
to America. It is a scheme involving danger, excitement and rich
rewards.”

He paused impressively. In spite of himself, Nat’s eyes began to dance,
his pulse to beat a bit faster. Adventure was as the breath of life to
the young leader of the Motor Rangers, and, to tell the truth, he had
faced the prospect of a life of inactivity with mixed feelings.

“Well, sir?” was all he said, however.

The scientist continued, with apparent irrelevance.

“You three lads, from what you have told me, have operated motor cars,
motor boats, and endured much in both forms of transportation?” he
asked.

Nat nodded.

“I guess we’ve had our share of the rough along with the smooth,” he
said briefly, but he was listening closely.

“What would you say to trying a voyage in the air?” was the question
that the man of science suddenly launched at him without the slightest
warning.

Nat glanced up from his steering amazed. The scientist met the lad’s
gaze firmly.

“Well?” he demanded.

“I—I—upon my word, I don’t know,” stammered Nat.

For once in his life, the young leader of the Motor Rangers was fairly
taken aback.




                              CHAPTER VII.

                        A STRANGE SAIL APPEARS.


“I am perfectly serious,” resumed Professor Grigg solemnly.

“The idea was such a new one that I admit it staggered me a bit,”
explained Nat hastily.

“Suppose you summon your friends, and I will explain in more detail,”
rejoined the professor.

Joe, who was polishing up the brass work and putting things to rights
generally on the storm-battered craft, was nothing loath to obey Nat’s
summons to the bridge. Ding-dong Bell announced that his engines were
in good running order and could be left to themselves for a time. So it
was not long before they all, including Mr. Tubbs, were grouped in
interested attitudes about the man of science.

“As Mr. Tubbs knows,” said the professor, “it was our original plan to
resume our voyage on the _Tropic Bird_, following our observations and
picture making at the volcanic islands. Our destination was to be the
coast of Chile. From there we were to go in search of a lost Inca city,
which is described in documents recently discovered.”

“G-g-g-g-g-gee wer-w-w-w-whiz!” sputtered Ding-dong.

“Hush!” admonished Nat, who could hardly attend to his steering for
interest. As for Joe Hartley, his eyes fairly bulged in his head.

“A lost Inca city,” he murmured. “Sounds good to me.”

“Is nothing known of the location of the place?” inquired Nat.

“Not except in a general way,” was the reply. “It is known to be
situated on an island in the midst of a lake high up on an Andean
plateau in Bolivia.”

“Like the one on Lake Titicaca in Peru,” said Nat.

“Ah, you have read of that?” said the professor approvingly. “Yes, from
the documents which came into the possession of the institute as the
gift of a traveler in Chile, it is probable that the ruins which I am
commissioned to search for are very similar in character to those you
have mentioned.”

“How are they to be reached?” asked Joe.

The professor smiled.

“From what we have been able to learn,” he said, “earthquakes have
destroyed the roads formerly used, and there is no way of reaching the
lake by land——”

“Then—then——” stammered Ding-dong helplessly.

“One must fly to them,” said the professor as calmly as if he were in a
class-room. “Thanks to modern science, I believe it may be possible at
last to obtain pictures and priceless relics of that forgotten
civilization.”

“But where are you going to get an airship?” asked Nat, when he had
recovered his breath.

As for Joe and Ding-dong, they regarded the professor in silent
amazement. Mr. George Washington Tubbs merely grinned. Clearly, the
idea was no startling novelty to him.

“That has been arranged for,” rejoined the professor. “A dirigible
balloon of the most modern type is already at Santa Rosa, a small town
on the Chilian coast. Before leaving the States, I took some lessons in
operating such a craft; but really, that was hardly necessary, as Mr.
Tubbs is a fairly expert operator of dirigibles, and has a knowledge of
their construction and machinery.”

“Then all that you will have to do, when you reach this town, is to get
the dirigible ready and then start the search for the lost city?”
inquired Nat eagerly.

“That is all. It should not take long, either. The machine is packed in
numbered sections. For security it has been labeled ‘Merchandise,’ and
is in charge of the American consular agent, who alone knows what the
boxes really contain.”

“Excuse me for saying so,” stuttered Joe; “but it sounds like—like a
wonderful fairy tale.”

“It is one,” said the professor smilingly, “a fairy tale which, with
the aid of you boys, I hope to make true.”

“With our assistance?” echoed Nat in an astonished tone.

“Yes. I really believe that it was Providence that threw me in the path
of you boys. You are exactly the type of self-reliant, clever young
Americans that I need for assistants in the work. Are you willing to
charter the _Nomad_ to me, land me on the South American coast, instead
of in California, and give me your services, for a substantial
compensation?”

“I—I beg your pardon,” Nat managed to choke out, “but the idea is so
entirely new to us that I think we shall have to hold a consultation
first.”

“Take your time,” said the professor airily; “take your time. It is
characteristic of me to arrive at quick decisions, as Mr. Tubbs knows,
and I don’t mind telling you that I shall be very disappointed if you
don’t see your way to accommodate me. We are now almost on a straight
course for the coast of South America. If, on the other hand, we landed
in Santa Barbara, I should have to take steamer from San Francisco to
South America, and I might arrive too late.”

“Why?” demanded Nat. “Is there any one else in search of the lost city?”

“My colleagues fear so,” was the rejoinder. “The documents passed
through many hands before they reached scientific ones, and the
treasures of the lost city, if they come up to all accounts, are enough
to tempt any one to search for them for their intrinsic value alone.”

“Have you any idea who the men are who may prove your rivals?” asked
Nat.

“I have—yes. But I do not wish to discuss that phase of the matter any
more just now. Suppose you and your friends hold your consultation and
then notify me of its result?”

“Very well,” agreed Nat.

Leaving the wheel in charge of the rubicund-headed Mr. Tubbs, who was a
capable steersman—indeed, there didn’t seem to be much he couldn’t
do—the boys withdrew to Ding-dong’s domain—to wit, the engine room.

They were below for about fifteen minutes.

When they reappeared, Nat’s face bore a radiant expression. He walked
straight up to the scientist, who was gazing at the sea with an
abstracted look as he studied the various forms of life that were
visible in the clear water.

“Well?” he asked, facing around, clearly anxious for “the verdict.”

“Well,” repeated Nat with a smile, which was strangely at variance with
his words, “I regret to report that we cannot undertake the commission
you proposed——”

“What! You cannot? But I——”

“That is,” continued Nat, “for any compensation. But we will agree to
land you and your companion at the port you desire, and further than
that, we will, from that time, place ourselves under your orders in the
hunt for the lost city.”

As Nat spoke these words, the dignified man of science actually capered
about, and snapped his bony fingers in huge delight.

As for Mr. Tubbs, he gave a wild “Hurr-oo!” of delight.

“Hurrah for the Grigg’s expedition!” he cried.

“Three cheers!” ordered Nat, and they were given with a will. The
echoes were still ringing out, when Nat gave a sharp exclamation, and
pointed to the eastward.

“A strange sail!” he cried, as they all turned eager eyes on the
distant speck of canvas.




                             CHAPTER VIII.

                        TRAPPED BY TWO RASCALS.


“Why! why, that’s the _Tropic Bird_!” exclaimed the scientist in
astonishment, as they drew nearer rapidly to the vessel Nat’s keen eyes
had espied.

“It is, indeed,” reiterated Mr. Tubbs, his red hair seeming to bristle.
“Oh, the cowardly pack of rascals! I’d just like to run alongside and
give them a bit of my mind.”

“They deserve it, certainly,” admitted the professor; “but I think we
had better ignore them.”

But as they came close enough to the schooner to perceive her clearly,
they saw that she carried her ensign reversed. This is a signal of
distress which there is no ignoring at sea, and is the universal sign
of imperative need on the part of the craft displaying it.

“We must see what they want,” declared Nat, setting his wheel over and
changing the course of the Motor Rangers’ vessel.

“Got any fresh water?” hailed a voice, as they came alongside.

The man who uttered the appeal was a powerfully built fellow, with a
plentiful crop of black whiskers, which gave him a ferocious expression.

“That’s Captain Ralph Lawless,” whispered the professor to Nat.

At the same instant, the skipper of the _Tropic Bird_ appeared to
recognize the professor.

“Why, surely that’s Professor Grigg?” he cried out, apparently in great
astonishment.

“Yes, it is, you cowardly rascal,” burst out the professor, his anger
overmastering his usually placid disposition. “What do you mean by
deserting us in the manner you did? We might have perished if it had
not been for these brave lads and their vessel.”

“Well, I’m sorry,” muttered the man, as the Motor Rangers’ vessel drew
in close alongside, “but I couldn’t help myself.”

“Couldn’t help yourself?” echoed the scientist, still angry. “How was
that, pray?”

“Why, I felt my schooner being drawn in toward the islands. If I hadn’t
‘cut stick’ when I did, we’d all have been lost, and I don’t see how
that would have helped you.”

This answer mollified the professor somewhat.

“So now you are in distress?” he said.

“Yes. We have run short of water. Can’t those kids let us have some?”

“You’ll have to ask ‘those kids,’ as you call them,” said the
professor, with some disgust.

“How much do you want?” asked Nat, who felt less and less liking for
the captain of the _Tropic Bird_.

“Oh, a few gallons will do. I know an island not more than a day’s sail
from here, where I can refill my tanks.”

At this point, another man—a short, stout fellow, like the captain—came
bustling up.

“Hullo, there, professor!” he hailed in an impudent voice. “So you came
out all right, after all. Are you coming on board?”

“I am coming on board to get my things, Mr. Durkee,” was the response,
“but I am not going to continue my voyage on the _Tropic Bird_.”

The captain looked rather dismayed at this.

“Oh, come now,” he said, “let bygones be bygones. I should be in a fine
fix if I sailed home without you.”

“You ought to have thought of that when you deserted us in that
cowardly fashion during the magnetic storm,” rejoined the professor.

The deck of the _Nomad_ was almost on a level with the top of the
schooner’s bulwarks, so it was easy for the professor to step from one
craft to the other. He now did so, disdaining the proffered aid of
Captain Lawless and his mate.

Mr. Tubbs joined him, and the two went immediately into the after-cabin
of the schooner, where they had lived while on board.

While they were collecting their belongings, Nat and Joe filled a
twenty-gallon keg with drinking water, and it was hoisted to the
schooner’s deck. It was really more than they could spare, but Nat was
a generous lad, and figured that, if necessary, they could go on short
allowance till the South American coast was reached.

During the time that the boys were about this work, Captain Lawless and
his mate had been holding a consultation in the lee of the deckhouse,
just aft of the foremast.

“It’s going to make lots of trouble for us if we arrive in America
without the professor or that chap Tubbs,” said the mate. “Besides
that, too, we’ll have lost our chance of sharing in that hunt for a
lost city. There ought to be enough loot in that to make us both rich.”

“That’s so,” agreed the captain. “If what those papers of the
professor’s say is right, that place must be paved with gold, and when
it rains it must drop diamonds.”

“Pretty near,” grinned the mate, in appreciation of his superior
officer’s humor. “I wish I’d had time to go over the papers more
thoroughly before that kid’s craft overhauled us. That was a good guess
of yours that they’d pick up the old gent and that chap Tubbs, and the
reversed ensign was a good way to get ’em to come alongside.”

“Well, now that we’ve gone this far, we may as well take the next
step,” observed the captain.

“And what’s that?” asked the mate, with a peculiar glint coming into
his little rat-like eyes.

“Why, fix it so that it won’t be possible for old Grigg to make trouble
for us in the States.”

“How?”

“Simple enough. We can easily overpower those kids, and as for the
professor and Tubbs, we’ll lock ’em in the cabin.”

“Say, cap, you are a schemer!” observed the mate, in rather sarcastic
admiration, “and then I suppose we’ll sail for home and be arrested and
imprisoned as pirates?”

“Not at all,” was the reply. “We don’t need to go home. South America’s
good enough for me. It’s Chile that the old cove is headed for, ain’t
it?”

“So his papers said.”

“All right, then. We’ll make the whole bunch prisoners, land ’em on an
island some place, and then we’ll sail on to Chile ourselves, and have
a try at finding this old lost city. By the way, did you make a tracing
of that map you found in the professor’s desk?”

“Did I? Well, I should say so. I’ve got it in my pocketbook now. That’s
likely to mean dollars and cents to us later on.”

“That’s so. Now then, you go and tell the crew what we are going to do.
They won’t cut up rough about it, especially if they think there is
money in it.”

“All right. I’m off. But see here, how are you going to do it? Those
kids look pretty husky.”

“Bah! What can they do against eight of us? If they get too
obstreperous, a tap on the head with a marlin-spike will soon quiet
them.”

While the two worthies of the schooner were cold-bloodedly discussing
their plans to save themselves from the consequences of their cowardly
act and at the same time enrich themselves, Nat and Joe, blissfully
ignorant of any such proceedings, had hoisted the water keg on board.

This done, they started aft toward the cabin to join the professor and
Mr. Tubbs. They found the two companions below, busily packing up their
possessions. But at the instant they entered, the professor looked up
from his desk, where he was sorting papers, with a troubled expression.

“What is the matter, professor?” inquired Nat politely.

“Somebody has been tampering with my papers!” he exclaimed. “I had them
arranged in a peculiar manner. And see, this lock has been forced. Oh,
that rascal of a captain! If we were in a civilized port, I’d——”

The professor’s angry tirade was interrupted in a startling manner. The
door at the head of the companionway stairs was slammed abruptly to.

Warned by some intuition which he could not have analyzed, Nat bounded
to the stairway and strove to reopen the door. But it resisted his
stoutest efforts.

“It’s locked!” he managed to gasp, as the truth burst upon him.

“And we have been trapped by those two rascals!” exclaimed the
professor.




                              CHAPTER IX.

                             SOME STRATEGY.


The first effect of a sudden and utterly unexpected disaster is,
usually, to produce incredulity in its victims. It was so in this case.

“Nonsense,” spoke the professor, more sharply than was his wont, “I
guess, after all, I am mistaken; it must be an accident.”

“If so, it’s a remarkable one,” said Nat grimly. “The bolt has been
slid into a hasp on the outside.”

“Woof!” ejaculated Mr. Tubbs. “Then we are in the position of the mouse
that wandered into a nice snug trap.”

“That’s the way it looks to me,” was Nat’s rejoinder. “What do you make
of it, Joe?”

The stout lad had, by this time, joined Nat on the stairway. But their
combined efforts failed to budge the door.

“It’s locked sure enough,” replied Joe. “Hush!”

“What’s up?”

“I thought I heard a sound of whispering on the outside.”

“So did I. That means there is some one out there listening to see how
we are taking it. Let’s give the door a good pounding. Maybe we can
make them give some explanation.”

The idea was voted a good one. The two lads shook and banged on the
door with all the vigor they possessed.

They were rewarded by hearing a gruff voice growl out:

“Ain’t a bit of use your shaking that door. It’ll hold till we get good
and ready to open it.”

“That’s Captain Lawless,” declared the professor.

He raised his voice.

“What do you mean by this outrage?” he loudly demanded.

“Now, perfusser, don’t get hot in the collar,” was the rough advice
hurled back at him. “I knows what I’m doin’. You don’t think that I’m
goin’ to stand trial before a maritime court just on your account, do
you?”

“You precious rascal!” hailed Mr. Tubbs. “I’d like to have my hands on
you for about five minutes.”

No rejoinder came this time. Evidently the skipper was not in a mood to
bandy words. As a matter of fact, he was half beginning to regret his
action in imprisoning the adventurers. To use the vernacular, he was
rather apprehensive that he had “bitten off more than he could chew.”

“We’ve got to get out of this somehow.”

It was fifteen minutes later, after an interval devoted to a discussion
of their situation, that the professor spoke.

“Agreed,” struck in Mr. Tubbs, “but how in the name of the immortal Abe
Lincoln are we going to do it?”

“I’ve got an idea,” said Nat suddenly. “See that old lounge in the
corner there?”

They nodded and waited for his next words.

“It’s old and rickety, but it’s made of stout timbers. What’s the
matter with using that for a battering ram?”

“Excellent!” exclaimed the professor, catching his meaning. “But what
are we going to do if we get out of here?”

“That’s a logical inquiry,” said Mr. Tubbs. “We haven’t got any
weapons, and those rascals may be well armed. I know that the captain
and the mate always carry revolvers. I’m not sure about the others,
though.”

“Humph!” murmured Nat. “I hadn’t thought of that. Tell you what we can
do, though. Let’s make a search of the cabin. Maybe we can find some
pistols or other weapons in one of them.”

“A good idea,” agreed the professor; “we’ll start by examining the
captain’s boudoir.”

They had hardly commenced their search of that worthy’s room, before a
shout from Joe announced that he had made a discovery. It was nothing
more nor less than a pistol in a case. On the wall, too, apparently as
an ornament, hung an aged and rusty looking blunderbuss.

“Hurray!” cried Nat; “that’s something, anyhow. Professor, you take the
pistol and I’ll——”

“If it’s all the same to you,” interrupted the man of science, “I had a
good deal rather you boys took the weapons. I am short-sighted, and I
know that my friend Tubbs is not over familiar with firearms——”

“Except in a shooting gallery at Coney Island,” put in Mr. Tubbs
apologetically.

“Very well, sir,” said Nat. “Joe will take the blunderbuss and I’ll
carry the pistol. Wonder if that old blunderbore is loaded, anyhow?”

“I’ve got an idea for testing it,” said Joe.

“What’s that?”

“Look here, why wouldn’t it be a good idea to place the muzzle of this
ferocious weapon to the door at the point where we think the lock is
located? If it is loaded, it’s pretty sure to have enough slugs in it
to carry away the lock, and the rest we’ll have to chance to luck.”

“That’s a good suggestion, too. At any rate, it won’t do any harm to
try it. We can’t be worse off, unless that rascally captain makes us
walk the plank or something, and he wouldn’t dare to do that, I guess.”

“Let’s see if there aren’t some more shooting-irons lying round loose,”
suggested Mr. Tubbs; “seems to me that mate always had some in his
room.”

But a visit to the mate’s room resulted in the discovery of nothing
more formidable than a pair of ancient cutlasses, hung crosswise on the
wall. The professor and Mr. Tubbs helped themselves to these, the
latter flourishing his in a truly awe-inspiring manner.

“How do you like the weapon?” asked Nat, who, despite the seriousness
of their position, could not forbear smiling at the moving-picture
man’s antics.

“Man alive!” rejoined Mr. Tubbs, “I only wish that it was possible to
get a moving picture of ourselves going into action.”

“Now then, Joe,” said Nat, when they had scoured the cabin
unsuccessfully for any more weapons, “it’s time for you to try your
stunt.”

Joe ascended the stairs and carefully placed the muzzle of the
blunderbuss in position under the spot where he was certain the lock
was situated.

“All ready?” asked Nat in a strained whisper.

“All right here,” responded Joe, his finger crooking on the rusty
trigger.

“Then let her go!” came the command.

But before Joe could press the bit of steel which he hoped would
discharge the gun, there came a startling interruption.

Bang!

Another gun had been fired outside. What could it mean?

“That’s the _Nomad’s_ gun. They are attacking her and trying to make
Ding-dong a prisoner!” cried Nat.

Bo-o-o-o-o-m!

The rusty throat of the old blunderbuss roared, and Joe was knocked
clean off his feet by the accompanying “kick.”

At the same instant the door was blown into fragments, and a stentorian
voice could be heard roaring out:

“Howling tornadoes! What’s that? A volcano?”

“Reckon somebody was taking a siesta on that door and old Mister
Blunderbuss disturbed him,” grinned Nat, as he caught Joe in his arms.

“Forward!” yelled Mr. Tubbs, brandishing his cutlass in the manner made
familiar by the heroes of naval pictures of the olden time.

The others caught the infection.

“Forward!” cried Nat, and, shoulder to shoulder, they plunged up the
companionway, burst through the shattered doorway, and rushed pell-mell
out upon the deck of the schooner.




                               CHAPTER X.

                         “DING-DONG” AND A GUN.


All this time Ding-dong Bell had been making history in a fashion all
his own. The lad had been below, pottering about his beloved engines,
at the time that the others had gone aboard the schooner, and
consequently was quite unaware of what had occurred till he emerged on
deck and found that the Motor Rangers’ craft was deserted.

“Guess they’ve gone aboard the schooner,” thought the lad, and was
preparing to follow, when a sailor, stationed at the latter vessel’s
main shrouds, to which the Motor Rangers’ boat was made fast, stopped
him.

“Stay where you are, young feller,” he ordered crisply.

It was at this moment that Ding-dong’s sharp eyes noticed a little
group, consisting of the captain, the mate, and several of the sailors,
standing aft by the cabin companionway.

“I want to join my friends,” exclaimed Ding-dong, forgetting to stutter
in his righteous indignation at the fellow’s tone and manner.

“Guess your friends ain’t receiving company, except by permission of
Captain Lawless,” was the reply given, with an impudent grin.

As the man spoke, he made a motion as if to grab Ding-dong, who was
standing with one leg on board the _Nomad_ and the other on the
schooner’s bulwarks.

But Ding-dong was quite as quick in his actions as were his two chums.
Moreover, he was a muscular lad, and his thews and sinews had been
toughened to a steel-like fineness by his many adventures.

Consequently, as the sailor rushed at him, the lad merely caught the
man’s outstretched arm, and, by a trick that he had learned from Nat,
gave it a sudden twist.

“Ouch!” grunted the fellow, and, without making any more fuss, he
writhed almost double and fell in a heap. But as he did so, Captain
Lawless spied what was going forward. In the haste with which the plans
to capture the Motor Rangers and their friends had been made, the fact
of Ding-dong Bell’s existence had been temporarily forgotten by the
rascally skipper and his mate. This sudden appearance, then, of one of
the Motor Rangers, alive and intensely active, was very disconcerting
to them.

“Confound you, boy; where did you spring from?” roared Lawless, as he
dashed at Ding-dong like an angry bull.

“Fer-fer-f-from under a go-go-gooseberry bush,” sputtered Ding-dong,
giving an agile backward jump, which brought him upon the deck of the
Motor Rangers’ vessel.

At the same instant came a thunderous sound from the cabin door
beneath, which, as we know, the imprisoned party were pounding and
rapping.

The sound told Ding-dong the whole story as plainly as if it had been
put into words.

“What have you done with my friends?” he demanded.

“Never you mind. Just throw up your hands and come on board this
schooner or it will be the worse for you.”

“No, thank you,” parried Ding-dong, his speech quite distinct in his
indignation and excitement, “I guess I know when I’m well off.”

“You brat, I don’t propose to be thwarted by such a whipper-snapper as
you. Come on board at once, I say!”

“Not to-day, thank you. Call around to-morrow,” scoffed Ding-dong.

As he spoke, the lad rapidly made his way forward over the turtle back
of the _Nomad_.

A sudden idea had come to him. On this turtle back was situated the
rapid-firing gun which was a part of the craft’s equipment. Joe had
been polishing it that morning, the cover was off and it looked ready
for instant action.

With cat-like activity and swiftness, Ding-dong made for the implement
of destruction. Reaching it, he took his stand on the small platform on
which it stood.

Before the astonished Captain Lawless could scramble after the lad,
Ding-dong had swung the gun on its swivel, and the captain found
himself gazing straight into its formidable looking muzzle.

Ding-dong had his hand on the firing lever, and the rascally skipper
went white as ashes as for an instant he thought the lad was going to
discharge it.

“Don’t! Don’t shoot!” he begged abjectly.

“Then you get right back where you belong,” ordered Ding-dong.

Just then he noticed that several of the crew of the schooner were
about to follow their captain on board.

“You fellows, too,” ordered the boy in a sharp, shrill voice, which
nevertheless rang with determination.

“I’m ver-ver-very nervous,” he went on, “and at any mum-mum-moment I’m
likely to give this lever a twist.”

“I’ll get even with you for this, my hearty,” muttered the nonplussed
Captain Lawless, but nevertheless he scrambled back after his crew as
Ding-dong gave his crisp command.

“Now, then,” cried the boy in a determined tone, “you let my friends
out of that cabin, or I’ll have to indulge in some target practice with
your schooner as the bull’s-eye.”

“Not much you won’t!” roared out Durkee, the mate.

As he spoke, the fellow whipped out a pistol and aimed it at Ding-dong.

The lad depressed the breech of the gun and gave the lever a twist.
Instantly a sputter of bullets flew forth. They lodged in the
schooner’s spars and rigging, sending a shower of splinters all about.

At the same instant, the roar of the blunderbuss sounded from the
cabin, and a fat sailor, who had been sitting on the door, bounded into
the air. He was not hurt, but imagined that a mine had exploded beneath
him.

As the adventurers rushed out of the cabin, they came face to face with
a scene in which Ding-dong Bell was the dominating factor. The moral
effect of the machine gun’s discharge had been tremendous. Palefaced
and demoralized, Captain Lawless and his crew fled forward, where they
huddled in a mass like so many frightened sheep.

“Say, professor!” hailed Lawless, “call that young gad-fly off. He’s
done a hundred dollars’ worth of harm to my ship already. Call him off,
do you hear?”

“It would serve you right if your schooner was sunk,” retorted the
professor. “What did you mean by imprisoning us in that cabin?”

“It was just a joke,” pleaded Lawless, whose face was pallid. He paid
no attention to the promptings of his mate, who was urging him, in an
undertone, to “stand up to the lubbers.”

“We’ll give in, professor,” he went on in a shaky tone. “You’re welcome
to take all your baggage and go, without us making any more trouble.

“How can we depend on you?” asked the professor.

“I’ll give you my word,” said the captain.

“A whole lot of dependence we could place on that,” scoffed Mr. Tubbs.

“Tell you what,” spoke Nat; “let’s make him lock all his sailors up in
the forecastle. We can guard them, and then, in case of treachery,
we’ll only have two to deal with.”

The professor delivered this ultimatum. Captain Lawless readily agreed
to comply with it. The crew, sullen and muttering, was ordered below,
and the forecastle hatch battened down. Joe was set to guard it, while
the others helped in the work of transporting the baggage on board the
Motor Rangers’ craft.

Of course Ding-dong Bell, who had really displayed the qualities of a
capable general, came in for much warm congratulation. He took his
honors modestly.

“I dud-dud-didn’t know it was lur-lur-loaded,” he protested, and, as a
matter of fact, the lad had been as much astonished as any one at the
tremendous fusillade that followed his manipulation of the
machine-gun’s firing lever.

At length all the baggage was on board. During its transportation,
Captain Lawless and his mate had looked sullenly on, but offered no aid
or interference. They were beaten men, and they knew it. Once the
professor’s report of their conduct was circulated, there was not a
civilized port into which they could take the schooner without being
arrested and brought to book for their misdeeds.

But they watched the Motor Rangers board their own craft and cast off
the lines without show of any emotion on their stolid countenances.

“You can release your crew now,” said Nat, when Joe had clambered on
board. As he spoke he rang the bell for the “Go ahead.”

The _Nomad_ began to forge through the water. By the time Captain
Lawless had reassembled his crew, the schooner was not more than a
speck to those on the _Nomad_.

“Well, that was a queer adventure,” said Nat, as they talked it over
that evening. “What a foolish man that skipper was to ruin his career
for the sake of spite!”

“Yes, he will be a marked man now,” spoke the professor. “In these days
of wireless telegraphy and other improved means of communication, there
is not a spot in the Seven Seas where he can hide his head without
being overtaken by the consequences of his folly and cowardice. I think
he was led into this thing by that mate of his, Durkee. He is a very
bad man.”

“Well, I guess they won’t bother us any more,” struck in Joe; “in fact,
my thoughts from now on are centered on the lost city and that cloud
cruiser of yours, professor.”

The professor smiled at the youth’s enthusiasm. Then Mr. Tubbs spoke.

“I reckon you folks have forgotten something,” he said. “That chap
Lawless has overhauled the professor’s papers. Don’t you think it’s
likely he may try to locate the lost city, too? It’s a stake worth
playing for.”

“Wow!” exclaimed Joe. “If that’s the case, look out for squalls.”




                              CHAPTER XI.

                    CAPTAIN LAWLESS TRIES TRICKERY.


“Do you intend to let them get away from us like this?”

It was Mate Durkee, of the _Tropic Bird_, who asked the question of
Captain Lawless, as the two stood leaning on the schooner’s rail,
watching the fast-diminishing form of the Motor Rangers’ capable craft.

The wind had fallen, and the schooner was dipping and rolling on the
swells, with her canvas flapping idly. The crew, grouped in a mass
forward, were watching their superior officers with some curiosity.
Plainly they were anxious to see how the situation was to be met.

“Well, what are we going to do about it?” demanded Lawless.

“I’ve got a plan, but it involves a good deal of risk,” was the reply.
“Are you willing to take a chance?”

“I’m willing to do almost anything to get even on that outfit,” was the
response, in a vicious tone.

“Then listen to me. I happen to know that we are not far from an island
where I’m pretty sure we can sell the schooner to the old chief for a
good price. When that is done, we can get a canoe from him and have
some of his men paddle us out into the track of that line of Dutch
steamers that run from Manila to Callao. If we spin a good enough yarn,
we can get passage all right.”

“Well, what then?” grunted Captain Lawless.

“Why, can’t you see? We’ll get from Callao to that Chilean port for
which that outfit is bound in very little time. Once there, we can use
our own judgment as to how to proceed. But I must admit, that I, for
one, mean to get a chance at the treasures of the lost city.”

“Suppose we did make that island you are talking of,” said Captain
Lawless, in tones that showed that the mate’s plan had made a deep
impression on him, “how soon would that Dutch steamer be going by?”

Mate Durkee made a rapid mental calculation.

“I used to run on the line, so I know their schedule pretty well,” he
said. “She should be going by by to-morrow night, at latest.”

“Humph! But you don’t seem to have taken the crew into consideration.
What are we going to do with them?”

“Oh, give them some sort of song and dance and abandon them. They can
live very well on the island till some vessel takes them off.”

This cold-blooded proposal seemed to banish Captain Lawless’ last
lingering trace of hesitation.

“It’s a good plan,” he said, “but a daring one. Suppose it ever leaks
out how we sold the schooner? There’ll be a clear case of barratry
against us.”

“So far as that is concerned,” urged Durkee, “we can’t be much worse
off than we are now, can we? That professor means to make things hot
for us in the States. I saw that in his eye. We must take refuge
somewhere, and Chile looks about as good to me as any place I can think
of right now.”

“I don’t know but what you’re right,” agreed Lawless. “Let’s go below
and look at the chart. How long ought it to be before we reach this
island, if we get a good breeze?”

“Not more than eight hours. If the wind picks up, we should make a
landfall before midnight.”

Some two hours later a spanking breeze arose out of the northwest. The
schooner’s sails bellied to it, and a spirit of joy was abroad among
the crew. Their officers had promised them a quick run to a fine
island, and then unlimited shore leave. Little dreaming of the trap
that was being laid for them, the crew went about their tasks of
trimming sails with songs and glad shouts.

When twilight fell the schooner was bowling along at a twelve-knot
gait, bound for the island of which Mate Durkee had spoken. It was
known to him as Brigantine Island, although the charts called it Cook’s
Land.

As the mate had foretold, it was not long after midnight when a cry of
“Land ho!” rang out from the forward lookout. It was bright moonlight,
and in the silvery radiance those on board the schooner had no
difficulty in making out a long, low elbow of land right ahead. Close
at hand they could hear the thunder of the surf as it broke on the reef.

“Do you know the passage?” asked the skipper of his mate.

“I could run it blindfold,” was the response. “Close haul on those
head-sheets!” he called out. “Lively, now! Bring her about! That’s the
way! Here, I’ll take the wheel myself!” he cried the next instant,
springing to the helm.

Under his skillful guidance, for there was no denying that the rascal
was an able seaman, the _Tropic Bird_ was swung through the narrow
passage-way in the reef, and shot into the calm waters of the lagoon
beyond.

“Don’t seem to be much life ashore,” said Captain Lawless, scanning the
moonlit island.

“Fire a rocket, and you’ll see the dingoes come running out of their
holes,” laughed the mate.

A big signal rocket was procured from the ship’s stores, and discharged.

As it burst in a cloud of blue flame, and the “bang” which accompanied
its bursting resounded loudly, lights began to flash on shore, and they
could see scores of dark figures scuttling about the white beach.

“What did I tell you?” said the mate, with a grin. “We’ll get a great
reception, all right.”

“They don’t happen to be cannibals, do they?” inquired Captain Lawless
timidly, his habitual caution asserting itself.

The mate laughed.

“What a one you are to get scared, Lawless!” he said. “Your name don’t
fit you a bit. Cannibals, is it? I should say not. Those chaps are
mission natives—some of them—and as smart a bunch as you’d want to see.”

As there was no time to be lost, if they wished to carry out their
audacious plan, the captain ordered a boat lowered and he and his mate
went ashore immediately. The chief was soon found. In fact, he was down
on the beach. He recognized Durkee, who seemed to have some sort of a
hold over him, and negotiations for the sale of the schooner were at
once begun. Like most dealings with savage folk, it required a lot of
diplomacy to accomplish the desired end. The trading was carried on
under a palm-thatched roof, while natives with torches stood all about.

If the two white men had not been so engrossed with their own affairs,
they might have been inclined to admire the savage picturesqueness of
the scene. But, as it was, they devoted their attention strictly to
business.

The chief, who rejoiced in the name of Billy Bowlegs—an appellation of
which he seemed quite proud—proved an adroit old bargainer. He spoke
English well, and was to the full as shrewd as any Caucasian trader.

But at last they managed to “make a deal,” as the saying is. Billy
Bowlegs was in need of a good schooner, and had long coveted the
_Tropic Bird_, which was well known in those waters before Captain
Lawless acquired her. The chief was willing to give three hundred
dollars in cash and two valuable pearls, worth fully the same amount
each, for the craft.

As this was the best they could do, the two rascally white men agreed
on this figure, and Billy Bowlegs agreed to give them transportation in
a war canoe as far as the path of the Dutch liners, which passed to
seaward of the island by fifty miles or so.

The crew, carousing and enjoying themselves in their own rough fashion,
knew nothing of the departure of their captain and mate that morning,
nor did those two worthies wish that they should. By the time the
abandoned men awoke to the true state of affairs, Lawless and Durkee
were on board the Dutch steamer _Prinz Joachim_ of the Imperial Peru
and Manila Line, bound for Callao. They were regarded with much
interest on board the craft as two luckless mariners—rough but
honest—who had lost their vessel in the great magnetic storm.

And so, while the Motor Rangers were gleefully heading for the land of
the lost city, their two malignant foes were likewise speeding toward
South America on a fast, well-equipped vessel.




                              CHAPTER XII.

                         “GOOD WORK, MANUELLO!”


“Any sign of land yet, Nat?”

The professor put the question, as he stood beside the young leader of
the Motor Rangers on the bridge of the _Nomad_.

“I’ve noticed a sort of purplish mass, like a low-lying reach of
clouds, in the distance for some time,” was the rejoinder. “Do you
think that it can be the coast of Chile?”

“I think it is highly probable; we should be picking up the land by
this time. I think—heaven bless us!”

The professor clutched wildly at his head. But he was too late. His
latest “top-piece,” a cap that had belonged to Ding-dong Bell, was
whirled from his head into the sea.

“It’s an extraordinary thing,” he said with a kind of patient
resignation. “But I don’t seem able to keep a hat on my head at all.”

“So I’ve noticed,” rejoined Nat, with a sort of dry humor, “and that’s
the last spare one on board. You’ve had six since we left the volcanic
islands, and there are no others left.”

“Well, I suppose I must go bareheaded, then, till we reach land. It is
most annoying, though, really. I cannot account for it.”

Nat had a hard task to keep from laughing, but he managed to maintain a
straight face by dint of heroic resolution. Moreover, as the bridge was
protected by awnings of red and white striped material, he did not fear
that the man of science would suffer greatly from the sun.

It speedily became evident that what Nat had seen was indeed the coast
of Chile. By late afternoon they could make out the great mountain
masses which hang above the rather low lying coast.

“Gives one a kind of a thrill to think that if all goes well we’ll be
flying over those before long,” remarked Joe Hartley, as they all stood
grouped on the bridge, watching the distant land with interest.

“It certainly does,” agreed Nat.

It was three weeks since they had parted company with the schooner, and
the _Nomad_ had been somewhat delayed by bad weather. But, all things
considered, she had made a good run and all on board were in high good
humor as they foresaw the end of the voyage.

By nightfall they were entering a landlocked bay that forms the harbor
of Santa Rosa. It seemed to be a tiny place, as well as they could
judge. Above the huddle of houses there rose the inevitable twin towers
of the cathedral, however, and through the glasses they could make out,
with a thrill, that Old Glory was flying over one of the buildings, no
doubt the American consulate.

“I tell you, that old flag never looks so good as when you see it
flying in a foreign port,” observed Mr. Tubbs, a sentiment which they
all echoed.

As soon as they had anchored, their craft was surrounded by a fleet of
boats from the shore. It was dark, and in the blackness the tiny lights
carried by the swarming craft made them resemble a fleet of fire-flies,
as Nat poetically remarked.

“I am going to take a boat ashore,” said Professor Grigg, as soon as
everything had been made snug. “As we wish to start on the expedition
as soon as possible it is important that I should see Mr. Stowe, the
American consular agent, without delay. I am anxious, too, to know if
the sections of the dirigible arrived in good shape.”

“By the way, professor,” asked Nat, “what is the airship’s name?”

“Why, bless my soul, I hadn’t thought of that,” remarked the man of
science, “she ought to have one, too. What would you suggest?”

“I think _Discoverer_ would be a good name,” said Joe.

“Dd-d-d-dish coverer?” inquired Ding-dong mildly.

In the scuffle that ensued, the lively young engineer of the _Nomad_
was almost toppled overboard.

When quiet was restored, the professor said that he thought that
_Discoverer_ was a very good name. And so it was decided upon.

“You may come ashore with me, if you like,” said the professor to Nat.

“If I like,” echoed that lad; “of course I’d be delighted to,” he added.

Accordingly, a few minutes later they set out in one of the shore boats
for the city, leaving behind them two youths with rather long faces.
Ding-dong and Joe would have dearly loved to share in the expedition,
but their presence on board was necessary, as the _Nomad_, after her
long, rough cruise, was badly in need of a “general housecleaning.”

“I guess the consul will be astonished when he learns of the manner in
which I have traveled here,” remarked the professor; “naturally he was
expecting me on the schooner.”

“Speaking of the schooner,” said Nat as the native rowers propelled the
long, narrow boat swiftly through the water, “you don’t anticipate any
trouble from Lawless or Durkee?”

“No, I do not,” was the rejoinder; “in the first place, the schooner
could not arrive here for many days, even if they had made up their
minds to follow us. By that time we shall be, I hope, far advanced into
the upper regions of Chile.”

As the professor spoke one of the boatmen gave a shout. Nat looked up
and saw that a sailboat was bearing right down on them at tremendous
speed. The outlines of two men could be seen, but it was too dark to
distinguish their features.

“Good gracious, if that man doesn’t tack he’ll run us down!” cried the
professor.

“He will indeed,” exclaimed Nat. “Hi there! Look out where you’re
coming!” he yelled, adding his voice to the outcries of the boatmen.

But the occupants of the sailing craft paid no attention. At a terrific
speed the larger craft bore straight down on the little boat.

The boatmen stood paralyzed with fear. They did nothing. Suddenly one
of them dropped on his knees, and began imploring the protection of the
saints.

Nat sprang toward him, almost upsetting the frail boat as he did so.
With a quick movement he seized one of the paddle-like oars, and by
exerting all his strength as he thrust it into the water, he managed to
send the boat spinning out of harm’s way.

The next instant the sailing craft flashed by, almost grazing the bow
of the small craft.

“You’re a nice pair of irresponsible idiots,” yelled the indignant Nat.
“Do you know you almost ran us down?”

A yell of derision came from the other boat, and at the same instant
something heavy whizzed past Nat’s head, almost striking him. It fell
in to the water with a splash.

“They threw something at me, an iron weight, or a rock, or something,”
exclaimed Nat as the sailboat, still going at the same rapid rate,
vanished in the darkness. “What do you make of such conduct?”

“I don’t know what to think,” rejoined the professor. “I was inclined
to believe at first that the sailors of that craft were merely
careless. But the throwing of that weight puts a different complexion
on the matter. It looks as if they deliberately tried to wreck us.”

“It does,” agreed Nat; “the whole thing is very mysterious. I’m sure I
don’t know why any inhabitant of Santa Rosa should wish us harm.”

But further discussion of the matter was cut short by the necessity of
arousing the boatmen, who were still stupid from fright. This was
accomplished at last, and the boat was sent whizzing through the water
again.

They were landed at a tumble-down wharf, and as the tide was out they
got the full benefit of the odors inseparable from a South American
town. Both, however, were too intent on the work in hand to waste much
thought on this.

The professor, who spoke Spanish, as did Nat after a fashion, inquired
the way to the consulate, and a ragged mestizo volunteered to escort
him thither. But to their disappointment, when they reached the
building, which served both as a dwelling and an office, the consul’s
assistant informed them that he was not expected for an hour or more.
They were invited to wait, however.

Professor Grigg, who was tired, gladly accepted the invitation, and
sank into a comfortable chair. But sitting still didn’t much appeal to
Nat.

“I guess I’ll stroll about the town a little and meet you here later,”
he said to the professor after a few moments.

“Very well, my lad. But be careful,” was the reply.

“Oh, I’ll be very cautious,” laughed Nat; “at any rate, I can’t get run
down by a boat ashore here.”

“But there may be dangers, nevertheless,” counseled the professor.

Nat again promised to be careful and hurried out. He wished to mail
some letters home, as well as do a bit of sight seeing. He found the
post office without difficulty and, having mailed his missives, was
leaving it, when a native, in a long serape, or cloak, glided up to him.

“The señor is from the boat which anchored this evening?” he asked.

“Yes,” rejoined Nat. “Why?”

“Because if the señor wishes to see the town I am very good guide. I
can show him where they sell veree fine ’Merican ice cream soda.”

“By ginger! You’re on,” cried Nat, who had a weakness for ice cream
sodas; “lead on, Macduff. You don’t look very presentable, but I guess
that isn’t your fault.”

“Thees way, señor,” said the man, and he walked off slightly in advance
of Nat.

Suddenly he turned into a dark alley. Now, although Nat had nothing to
dread, yet he began to be fearful that the fellow might mean to rob
him. So he stopped short for an instant. But the next moment his
suspicions were disarmed by a look at the ragged, pitiable fellow. Nat
would have been a match for six of him.

“Where are you going?” he demanded, however, as they plunged into the
narrow thoroughfare, which was ill-paved and black as a tunnel.

“A short cut, señor. A short cut to the Gran’ Plaza. We be there soon
now.”

“Well, let’s hurry up and get out of this, quick,” said Nat; “I don’t
much like——”

Smash!

Something struck the young Motor Ranger on the back of the head. He
extended his arms helplessly, and plunged dizzily forward, collapsing
in a heap on the pavement.

At the same instant two figures glided from a doorway and joined a
third, the one who had struck Nat the blow that felled him.

“Good work, Manuello,” said the voice of Captain Lawless. “Pick him up
and help us carry him in.”




                             CHAPTER XIII.

                        SOUTH AMERICAN JUSTICE.


Aided by the rascally guide, who had been employed for the express
purpose of decoying Nat, the three men carried the lad’s limp form into
the doorway. Inside they ascended a steep flight of stairs, and at
length arrived in a room on the upper story.

A lamp was smoking and flaring on a table, which, besides one chair,
appeared to be all the furniture there was in the place.

“Fling him on the floor,” ordered Captain Lawless brutally, and poor
Nat was chucked into a corner with as scant ceremony as if he had been
a sack of potatoes.

The appearance of both Lawless and his rascally mate was materially
changed since we last saw them leaving their crew marooned on the
tropic island. Both had shaved off their beards, and wore the South
American style of dress, so that it would not have been an easy matter
to recognize them.

The two rascals had arrived in Callao a week before, and at Lima had
exchanged their pearls for substantial sums, so that they were well
provided with money. They made no long stay at Lima, but hastened to
Santa Rosa, where Durkee fell in with two old acquaintances, to wit,
the two South Americans who were now leagued with them.

As soon as the news of the approach of the Motor Rangers’ craft spread
along the water front, Lawless and Durkee engaged a sailboat. They
wanted to look the craft over, and ascertain the lay of the land, as it
were. But, as we know, darkness fell before the _Nomad_ was anchored,
and they were chagrined to find no easy way of getting close to the
vessel. But they saw the professor and Nat leave her for the shore, and
made the cowardly attempt to run them down that we have related.

When this scheme failed, they hastened back to the port, landing at a
wharf not far distant from the one at which Nat and his companion had
disembarked. Having found their satellites, they deputed one of them to
track Nat and lure him into the alley where they lay in wait for him.
How easily and unsuspectingly the lad had walked into the trap, we know.

“What are we going to do with this cub, now that we have him?” asked
Lawless, as Nat was thrown into the corner.

“Better put him in Manuello’s pit downstairs,” said Durkee. “He’ll come
to in a minute or so and may make us a lot of trouble.”

Lawless bent over Nat and examined him carefully.

“You must have hit him a terrible crack, Manuello,” he said to one of
the South Americans, who stood by, impassive and indifferent, while
this dialogue was carried on.

The man shrugged his shoulders.

“What would you?” he said. “You told me to knock him senseless, and I
did so.”

“You certainly did,” said Lawless, with a brutal laugh.

“Well, if we are going to keep him in the pit over night, we had better
put him there now,” remarked Durkee.

“All right. Bear a hand in packing him down stairs again, then.
Confound it, I wish we hadn’t brought him up here. He’s a heavy
youngster.”

“He is that,” agreed Durkee. “And he’s got muscles like iron. He’d be
an ugly customer in a rough-and-tumble fight, all right.”

“No danger of such a thing as that occurring,” said Lawless, as he
lifted Nat’s feet, while Durkee took his head.

Followed by the South Americans, one of whom held the lamp, they
descended the stairs, and opening a trap-door in the passage, they
clambered down another flight leading into a damp, earthy-smelling
cellar. In the centre of this cellar, the light revealed a deepish pit.
Into this pit Nat was lowered. All this time he had given no sign of
consciousness and was as limp as a rag-doll.

“Now, get the dogs, Manuello,” ordered Lawless.

In obedience to his commands, the South American approached a small
door at the rear of the cellar and opened it. He whistled softly, and
two ferocious, half famished looking blood-hounds came leaping out.
Their dripping fangs were drawn back, exposing sharp, white teeth.

“Watch that boy carefully,” said Manuello in Spanish to the brutes.

They seemed to comprehend him instantly. They uttered a low growl and
crouched close to the edge of the pit. Their red-rimmed eyes were fixed
on the boyish form lying at the bottom.

The creatures were vicious to a degree; in fact, Manuello used them in
fighting, the scene of the brutal sport being the pit in which Nat now
lay.

“Humph!” said Captain Lawless, as he regarded the two dogs, “those
fellows are better than human guards. If that boy ever escapes from
them, he’ll be——”

“Look out!” yelled Durkee suddenly.

An astonishing thing had happened. Nat’s limp form had suddenly
galvanized into aggressive, fighting life.

He sprang erect like a flash, and in one bound was out of the pit.
Another instant, and his fist was crashing into Lawless’s face. The
man, taken utterly off his guard, reeled backward, waving his arms
wildly.

He fell into the pit with a crash and lay still.

Before Durkee could recover from his amazement, he, too, had joined
him. There remained only the two Spanish-Americans for Nat to face. But
they had had more time to prepare themselves. Both brandished
wicked-looking knives as the boy came at them.

Moreover, the dogs had now awakened to the situation. With frantic yaps
and snarls, they sprang at Nat.

The lamp which had lighted their progress to these lower regions stood
on the ground. Nat saw in it a weapon of necessity. Snatching it up, he
swung it round his head and then sent it crashing at the brutes as they
leaped for his throat.

As the crash of splintering glass resounded, the place was plunged in
darkness, but the howls of the two savage brutes showed that the
burning oil had singed their skins.

Without waiting an instant, Nat plunged off through the darkness, in
the direction in which he judged the door lay. As he dashed forward, he
collided with a body, no doubt one of the South Americans. Down went
the fellow before Nat’s onrush, just as if he had opposed him on the
football field.

But in the meantime, Durkee had recovered his wits and scrambled out of
the dog-pit. His rough voice came bawling through the darkness with
appalling ferocity.

Fear of this ruffian lent Nat winged feet. He found the door, darted
through it and then down the passage and out into the dark street. At
the far end of it he could see lights gleaming. He made for these at
top speed and found himself in a well-lighted plaza opposite the
cathedral.

He knew that the ruffians would not dare to pursue him there, and,
spying an _alguzil_, or native policeman, he made his way to him. In
Spanish Nat explained the outrage that had been perpetrated on him, and
demanded that the police investigate instantly.

To his astonishment, the man merely shrugged his shoulders, and twisted
his little black moustache. He said that nothing could be done that
night.

“To-morrow, perhaps, but not to-night, señor,” he replied, and turned
away to strut off on his beat once more.

“Gee whiz!” muttered Nat, as he watched this competent conserver of law
and order, “what wouldn’t I give for a good American cop with a big
nightstick, right now. However, it’s no good trying to wake that chap
up, and those rascals must have decamped by this time, anyhow. Wonder
if they meant to rob me, or what? Funny thing that two of the voices
sounded so familiar. If it hadn’t been for the impossibility of their
being here, I could almost have sworn that they were the voices of
Lawless and Durkee.”

As it was past the hour at which he had promised to return to the
consulate, Nat set off at a brisk pace. Once he had to ask his way. The
man he inquired of, a woe-begone looking personage in a long cloak and
a cone-shaped hat, replied with great volubility.

“I will guide the señor there,” he declared.

“I guess not,” rejoined Nat, with such vigor that the fellow fell back
a pace, “I’ve had all I want of guides in this place.”

As Nat walked along, he felt the back of his neck, where he had been
struck, for it was becoming quite painful.

“Good thing the force of that blow was mostly wasted on my shoulder,”
he said to himself, “or I might have been knocked unconscious in good
earnest. As it was, it was a lucky thing I shammed insensibility, or I
might have got another tap.”




                              CHAPTER XIV.

                      OFF ON THEIR STRANGE VOYAGE.


“Well, boys, everything appears to be all right.”

It was morning in the large compound, or garden, adjoining the consul’s
house, and our adventurers were grouped about an odd collection of
articles that had formed the contents of several big packing cases.

“By the way,” put in Mr. Stowe, who had been an interested spectator of
the unpacking of the cases, “I have news for you, Master Trevor.”

“What is it?” inquired Nat, whose shoulders still felt a bit stiff and
sore, but was otherwise in fine fettle.

“The police say that they will arrest that man who struck
you—to-morrow.”

“I thought so,” said Nat, with a laugh, as he caught a twinkle in the
consul’s eyes; “I guess it will be one of those to-morrows that never
come.”

“I’m afraid so,” said the consul. “There is little law in this country,
and it’s a case of every one looking out for himself.”

After some more talk, in which all freely expressed their indignation
against the rascals who had decoyed Nat, work on the erection of the
dirigible was begun. It proceeded rapidly. By afternoon the lower
framework of the craft was in position and bolted firmly in place. This
part of the craft merits a somewhat detailed description. It was of an
aluminum alloy, of great strength and lightness.

Amidships of the structure, which was shaped not unlike a long sleigh,
was a canvas-enclosed cabin. The front part of this was fitted with
round windows for the helmsman to see out of, and contained the wheel
by which the great rudder was controlled. The various levers and
handles for the management of the engine were also manipulated, like
the rudder, from this “pilot-house,” as it may be called.

Just aft of the pilot-house the canvas-enclosed framework did duty as a
dining, living and sleeping room, being fitted with swinging bunks,
which, when not in use, folded up against the ceiling. A collapsible
table and other furniture of the same character were also to be found
in this chamber, as well as a denatured alcohol stove for cooking, and
a complete outfit of plates, knives, forks, etc.

Behind the pilot-house came the heavy frames and stringers, destined to
support the engine. This was a six-cylinder motor of one hundred horse
power, which drove a big suction propeller attached to the front of the
framework. Thus the dirigible was drawn, and not pushed, through the
air. The propeller was ten feet from tip to tip, and formed of
laminated wood covered with canvas stretched tightly upon the timber.

A sort of gangway, or path, extended from bow to stern of this
framework, enabling the aerial navigators to walk to any part of the
structure at will.

The entire frame was secured to the vast gas bag by numbered ropes,
with steel cores to insure their stoutness. Relief valve-cords and gas
controls all ran to the pilot-house, under which structure a steel
tank, capable of holding two hundred gallons of gasolene, was
suspended. A reserve supply of fuel was also carried, as well as
lubricating oil, and what Joe Hartley called “a machine shop full of
tools.”

There were other features of the craft, which will be described as
occasion arises; but when we say that the _Discoverer_ was, roughly, a
hundred and fifty feet from stem to stern, one of the largest airships
of her type, constructed in America, had a capacity of 150,000 cubic
feet of gas and could lift 6,000 pounds, we have covered the main
features of her construction. It may be added that the motor was of the
four-cycle type, and, despite its high horse power, weighed but a
trifle over 250 pounds. Aluminum alloy had been used freely in its
construction.

By nightfall the engine was in place and firmly bolted to its
foundation plates. A test showed it to be working perfectly. The cabin
provision lockers were then stored with canned goods of all
descriptions, and staples, such as flour, beans, bacon, corned beef and
preserved butter. Tea was also carried, but no coffee. One feature of
the cabin was the “armory.” This was a chest containing rifles and
shotguns of the latest automatic type. It was an important feature of
the _Discoverer’s_ equipment, inasmuch as the adventurers expected to
“live on the country” to a great extent, for Bolivia abounds in game.

All that remained to do then, was to inflate the great gas bag. The
adjustment of this to the frame proved tedious work. But at last it was
done, and the folds all carefully straightened out, in itself an
arduous job. The whole party was pretty well tired out by this time,
and work was discontinued for the day.

“In the morning,” said the professor, “we will inflate the bag, and
then there will be nothing more to detain us.”

The boys gave a cheer. It seemed almost too good to be true—the idea
that before many hours had passed they would be flying high above old
Mother Earth in a cloud cruiser, that for completeness and
effectiveness surpassed their wildest dreams.

Between four and five o’clock the next morning the lads were astir.
After early coffee and some fruit and rolls, the task of inflating the
great bag was begun. Huge wooden tanks full of iron filings and metal
scrap had already been erected. Acid was now added to the filings and
the tops clamped on. Then the inflation pipes, purifier and nozzles
were adjusted.

A cheer broke from the boys as they saw the huge bag begin to swell
like a live thing as the gas poured into it. By noon the professor
announced the inflation as being sufficient. At that time, the great
yellow bag was as tight as a drum almost, and the heat of the sun
served to swell it still further. While the bag had been filling, the
under frame of the dirigible had been weighted down by bags of sand.
Otherwise it would have risen of its own volition.

The last things loaded on the framework were several cylinders of
hydrogen gas at tremendous pressure. This was the reserve supply of the
adventurers, and the tanks contained enough almost to refill the bag in
case of necessity. A hasty lunch was consumed at the consul’s table,
and Nat gave final instructions to the man who had been employed to
take care of the _Nomad_ during their absence.

This done, there was nothing else to wait for, and at one-thirty sharp,
the professor gave a final look over things. Then he turned to
Ding-dong Bell.

“You can take your place at the motor,” he said. “Mr. Tubbs, you will
attend to the handling of the craft as we rise.”

The versatile Mr. Tubbs, whose moving picture apparatus was in
readiness, paused to take a few pictures, and then mounted to his place
in the pilot-house.

Nat and his chums bade good-bye to the consul, and then took their
places. It was Nat and Joe’s task to attend to the throwing off of
ballast as they arose.

“Good-bye and good fortune to you,” said the consul, as the great
airship quivered and strained, as if anxious to be up.

The bags had been thrown off so rapidly that now the weight of only a
few held her down. The professor took his place beside Mr. Tubbs. The
consul’s wife waved a dainty handkerchief.

The departure had been kept a secret, but the sight of the great yellow
bag’s outlines rising above the compound walls had attracted a crowd
outside. A cheer arose as the _Discoverer’s_ electric siren sounded a
prolonged blast.

It was the signal for throwing off the remaining bags. Nat and Joe
worked with a will. Suddenly the craft bounded upward, almost throwing
them off. Hastily they cast off the final sacks, while Ding-dong, his
face pale with excitement, stood by his engines.

Clang-clang! came from the gong at his elbow.

The lad’s hand shoved over the starting lever that gave the engines
their first impulse by means of compressed air. Then he manipulated the
sparking and gas controls.

The mighty propeller began to beat the air as the _Discoverer_ soared
buoyantly, and yet in stately fashion, high above the houses and
tree-tops.

“Hurray! We’re off!” cried Nat, clambering along the runway as nimbly
as a sailor.

Faster and faster the propeller revolved. The wind was blowing lightly
out of the west, aiding the _Discoverer_ on her flight toward the
mountains.

Suddenly Ding-dong felt something fan the air past his ear. It was a
bullet. At the same instant a report came from below. Somebody was
shooting at the craft of the clouds. The others rushed out excitedly.
They were just in time to see two figures struggling in the hands of
several native policemen.

“It’s that rascal Lawless and his mate Durkee!” cried Nat. “Now I know
why those voices seemed so familiar. It was those two ruffians who
captured me the other night.”

“But how in the world did they get here?” asked Joe.

It was many days before that mystery was solved for the Motor Rangers,
but in the meantime they at least had the satisfaction of seeing that
the cowardly endeavor to injure the airship had resulted in their
arrest.

But they gave little time to thinking of Lawless and his fellow
ruffian. The land of mystery, of the lost city, of the unknown, lay
before them.

With a fair wind and with perfectly working engines, the _Discoverer_
drove forward at forty miles an hour, carrying the Motor Rangers on the
strangest cruise of their eventful lives.




                              CHAPTER XV.

                     A SIGNAL THAT MEANT “DANGER.”


Spinning along at a height the barograph showed to be 1,500 feet, was
an exhilarating experience. The slight feeling of apprehension which
the Motor Rangers had felt when they set out on their novel cruise,
soon wore off, and was replaced by a buoyant sensation.

“Well, Master Nat, what do you think of it?” inquired the professor,
emerging from the cabin and coming “aft” to where Nat was standing by
the smoothly running motor.

“It’s glorious,” replied Nat enthusiastically. “I had no idea, though,
that it was possible to get used to it so soon.”

“Well, a craft of this kind is vastly different from an aeroplane,”
commented the man of science. “It is my belief that the aerial
trans-Atlantic liner of the future will be a dirigible.”

“I wouldn’t mind undertaking the trip in the _Discoverer_,” declared
Nat, with glowing eyes and cheeks.

“What speed are we making?” inquired Joe Hartley.

“About forty miles an hour,” said the professor; “but you can tell the
exact speed by stepping into the pilot-house and examining the
instruments.”

The lads followed his advice, and found that the speed recorder
registered a shade more than the professor had assumed. Mr. Tubbs had
the wheel, and was gazing straight ahead, like a steamboat pilot.

The pilot-house of the _Discoverer_, in fact, was not unlike that of a
steamer, although much smaller, of course. The registers and
indicators, too, that were fastened to the walls, or rather the
framework of the _Discoverer’s_ “hull,” were totally unlike any that
the lads had seen before.

Joe Hartley, who had been appointed chief cook and bottle washer, soon
left, to begin his preparations for lunch. But Nat lingered on,
fascinated. Joe’s meal proved an excellent one, and the fact that they
were so high above the earth did not affect the boys’ appetites in the
least. In fact, Ding-dong Bell observed that he had never felt so
hungry in all his life before.

After the meal was concluded, the motors of the craft were slowed down
a bit, so as to economize on gasolene as much as possible. The fact
that the westerly wind had increased made it possible to slow the
engine down and still make good progress.

“I wonder what they think of us down below there?” said Joe, as he
stood by Nat’s side, leaning over the forward deck-rail and watching
the dwarfed figures of the inhabitants of a village above which they
were passing, scurrying to and fro like ants.

“I guess they must think we are some sort of demoniacal bird,” grinned
Nat. “Hark!”

Faintly, very faintly, borne to their ears, came the sound of church
bells ringing furiously.

“They must be going to hold services in our honor,” hazarded Joe.

“More likely they are going to pray that we don’t harm them,” responded
Nat. “According to the professor, the people of this country are a very
ignorant lot.”

By afternoon the _Discoverer_ was flying above rugged country. The
foothills of the great Andean range had been reached, and they were in
Bolivia. It gave the boys a thrill to think that they were actually at
last in the hoped-for vicinity of the lost city of the mysterious old
Incas.

                  *       *       *       *       *

As the sun grew lower, the great altitude to which they had attained
struck them with a sharp sense of chilliness.

“This part of the world ought to be called Chile,” observed Joe, as he
and the professor and Nat stood on the forward deck just below the
pilot-house.

“If you will come into the cabin and see what I have in that big chest,
we can possibly get over that difficulty,” said the professor, with a
smile.

The lads accompanied him within and found that the chest referred to
contained a variety of warm clothing.

“I knew that the late afternoons and nights on the Andean heights were
bitterly cold,” said the professor, as the boys selected some garments,
not forgetting a coat-sweater for Ding-dong. “I therefore took the
precaution to be prepared to meet them.”

It was not long after this that the professor addressed a few words to
Mr. Tubbs, and the _Discoverer_ began to drop. Then came a sudden
signal to Ding-dong to slow up his engines. This being done, the
lateral planes of the dirigible, which have not yet been mentioned,
were inclined at an angle that brought her to earth with an easy,
gliding motion.

“Are you going to land for the night?” asked Nat, who had watched the
maneuvers with interest.

“Such is my intention,” said the professor. “It is too late in the day
to get any observations now, and I don’t fancy traveling at night in
this region. We might blunder miles off our course.”

The boys agreed that this was so, and then gave their full attention to
what was going forward. Immediately beneath them was a charming,
park-like savannah, set in the midst of dense forests of gigantic
trees, from whose branches hung great twisted creepers, looking not
unlike big snakes.

It formed an ideal landing spot for the big dirigible, which, in a few
moments after the descending planes had been set, grazed the ground and
then settled. Instantly the professor shouted an order for the
anchoring process to begin.

The boys had been drilled in this before the voyage was started, and
fell to work with a will on their task. By running the propeller
slowly, with the descending planes set at a sharp angle, the
_Discoverer’s_ body was naturally held against the ground.

Nat and Joe leaped off on opposite sides, both armed with sledges. With
these heavy hammers they drove sharp, barbed steel stakes into the
ground till they were almost as firm as rocks. Each stake had a ring at
its top through which ropes were rapidly looped. The ends were then led
back on board and secured. This was done so that in case of a sudden
attack the great aircraft could be released by those on board. Of
course, in such an event, the stakes would have to be left behind, but
as an extra supply was carried, this would not be such a serious matter.

Ten minutes after she nestled to the ground, the _Discoverer_ was
secured as snugly as a vessel at her wharf. The engine was shut off and
the various necessary adjustments of the controls and apparatus of the
pilot-house made. This done, the entire party stepped “ashore” for the
first time in many hours.

“We will sleep on board, but cook our supper here,” decided the
professor.

This plan just suited the boys, and they scattered in all directions to
obtain firewood for the encampment. While they were doing this, Mr.
Tubbs set about the task of getting the needed utensils from on board
the cloud cruiser. He had been busily engaged on it for some time when
the professor looked up from some calculations he was making on the
back of an old envelope.

“It appears to me those boys are a long time gone,” he said. “I hope
they are all right.”

“Oh, they are all right,” spoke the moving-picture artist easily. “They
took the rifles with them, and agreed that in case of any danger or
difficulty befalling them, they would fire three times.”

“In that case——” began the professor.

But he halted with an abrupt exclamation of consternation. Mr. Tubbs’s
face likewise took on a perturbed look at the interruption.

From the forest, to their right, three shots, fired in rapid
succession, had resounded.




                              CHAPTER XVI.

                                INDIANS?


“What can be the matter?” was the exclamation that burst from the
professor’s lips.

“Something serious,” declared Mr. Tubbs. “Take a rifle and we’ll find
out.”

Hastily selecting a weapon each, the two friends plunged into the
forest in the direction from whence the shots had come.

“It’s ahead there, somewhere!” panted the professor, as the sound of a
mighty threshing and struggling amidst the undergrowth came to their
ears.

Neither the professor nor Mr. Tubbs was in the least faint-hearted, but
they crept through the forest with some caution. If the boys had been
attacked by enemies, they reasoned the best thing to do would be to
give their foes no opportunity of observing the approach of
re-enforcements.

------------------------------------------------------------------------

[Illustration: They came on a scene that, for an instant, almost
deprived them of their breath.]

------------------------------------------------------------------------

But, as the noise grew louder, they hesitated no longer, but pressed
right on. Suddenly, on emerging into an open space where the growth had
been flattened out in every direction, they came on a scene that, for
an instant, almost deprived them of their breath.

In the midst of the open space, Nat and Joe were bending over the form
of Ding-dong, who was stretched on the ground, seemingly unconscious.
Not far off, an immense snake, which must have been fully fifteen feet
long, was lashing wildly about in its death agonies.

“Oh, professor!” cried Nat, as he saw the newcomers, “we’re so glad you
have come. Ding-dong was attacked by that serpent and badly crushed. It
was only by firing at the creature that we managed to save his life.”

“Is he badly hurt?” choked out Joe anxiously.

The professor, who had been bending over the unconscious lad, shook his
head.

“Merely shock, and possibly a sudden weakening of the heart,” he said.
Taking a small vial from a pocket medicine-case, the professor forced
some of its contents between Ding-dong’s lips. In a few moments the boy
was able to sit up and take notice of things about him.

By this time the convulsive dying movements of the snake had ceased,
and it lay still.

“Ugh! What a monster!” shuddered Ding-dong. “I can feel his terrible
folds around me yet.”

As usual, when under the stress of emotion, Ding-dong’s hesitating
manner of speech had left him, and he enunciated quite plainly.

“How did it happen?” asked the professor.

“I was looking for wood,” explained Ding-dong, “and thought I had found
a f-f-f-fi-fine c-c-chunk of timber. But w-w-when I pu-pu-put my hand
on it, the ber-ber-blessed thing turned out to be a snake. I yelled at
the top of my voice, and started to run, but before I had gone far I
tripped and fell. The n-n-n-n-next instant the snake had me.”

“Joe and I were a short distance off,” chimed in Nat, taking up the
story, “and heard Ding-dong’s yell. We hurried to him, and you can
imagine how horrified we were to see him struggling with that serpent.
Joe raised his rifle, but then lowered it again. He was scared to shoot
at the snake for fear of hitting Ding-dong. But at last we saw a
chance. I fired once and Joe twice.”

“And all three bullets penetrated the brute in and about the head,”
struck in Mr. Tubbs, who had been examining the snake.

“So they did,” declared the professor, as he and the boys joined the
ruddy-headed one; “good shooting, boys. This snake is of the boa
variety. They are common all along this coast, but usually they are
thickest near rivers. As a rule, they will not attack human beings,
although cases have been recorded of their doing so. I imagine that it
was Master Bell’s having grabbed him that angered his snakeship. Shall
we take the skin for a souvenir?”

“N-n-n-no, thank you,” stuttered Ding-dong, “it will be no trouble to
re-re-remember that f-f-f-fellow without having to l-l-l-look at his
skin.”

“I agree with you,” said Mr. Tubbs. “I guess we’ll leave him here for a
while. It won’t be long before some animal or other makes away with it.”

Leaving the repulsive looking carcass on the ground, they set out to
return to the _Discoverer_.

“Well, all is well that ends well,” said the professor, as they tramped
along; “at first I had a dreadful fear that you lads had been attacked
by Indians.”

“Indians!” exclaimed Nat. “Are there Indians in this part of Bolivia?”

“Oh, yes; several tribes,” was the rejoinder.

“Are they savage?” inquired Joe.

“I am sorry to say that they are. In other parts some of the natives
have been converted to Christianity, but the natives of this section
are fierce and warlike. I hope we shall manage to steer clear of them.”

“What is the tribe called?” asked Nat.

“They are known as the Caripunas,” was the rejoinder. “The early
Jesuits had much trouble with them, and they have ever since remained
in a more or less wild and hostile state. They are very much averse to
having any one enter their country, and that was one of the minor
reasons why this trip was made by means of the dirigible.”

“Their country!” echoed Joe. “I should think the Bolivian government
would send a regiment up here and subdue the rascals.”

“Several such expeditions have been despatched,” was the response, “but
the fate of all has been the same. Several months after their departure
the remainder of the force has come straggling home, more dead than
alive, to tell a tale of death and defeat.”

“But how can Indians cope with civilized troops?” Nat wanted to know.

“For one thing, they are inured to the hardships of the forest,”
rejoined the professor; “for another, these Bolivian Indians wage war
with poisoned arrows shot from long blow guns. A man usually dies in a
few minutes after such an arrow has struck him, unless medical
attention is at hand. Armed with these weapons, the Indians creep up on
their foes and noiselessly decimate an entire force. It is in this way
that the Indians have managed to reserve this part of the country for
themselves and keep the hated white man out of it.”

The boys looked rather grave as they continued their tramp back to the
_Discoverer_.

“Looks to me as if we were in for a more exciting time than we
bargained for,” observed Nat to Joe.

“I guess you are right,” rejoined Joe. “A battle with Indians who
employ such deadly weapons does not appeal to me.”

“Oh, I guess we’ll get through without trouble,” exclaimed Nat. “At any
rate, if we are attacked, we can climb aboard the good old _Discoverer_
and soon be out of range.”

“That’s so,” agreed Joe, and the lads dismissed the matter from their
minds; but whether Nat’s surmise was correct or not, we shall see in
due time.




                             CHAPTER XVII.

                          A QUEER SORT OF GUN.


With the wood gathered by the young Motor Rangers, Mr. Tubbs soon had a
roaring fire going. By sundown it was so cold that they were glad to
huddle close to the cheerful blaze, which was for purposes of warmth
only, the cooking being done on the denatured alcohol stove belonging
to the galley of the _Discoverer_.

It was an odd meal, but one the boys enjoyed thoroughly. Mr. Tubbs was
as good a hand at cooking as he was at anything else, and as a supply
of fresh meat had been brought along, they had a capital meal, helped
out with choice canned vegetables and even, to celebrate their first
night in the land of their search, a generous portion each of plum
pudding. It was canned, of course, but quite palatable, or so the boys
appeared to find it.

After supper the professor gave the lads an interesting sketch of the
country they were in, and finished up with an account of the old Incas,
one of whose lost cities they had come to find.

Among other things of interest he told them concerning the lost race,
was that they are believed to have been sun worshippers. At any rate,
in one of the ruined cities which has been located in Peru, circular
temples with the walls embellished with pictures of the sun have been
found. Other facts concerning the vanished civilization of the Incas
must ever remain a mystery, said the man of science.

For instance, at the remains discovered in Peru, a huge rock, shaped
like a gigantic dome, was found. Traces of gold were discernible on its
surface, and it is believed that at one time the whole great,
monolithic mass was completely plated with this costly metal.

“Other strange features of these ruins,” went on the professor, “are
dungeon-like chambers which are believed to have been used in
cereomonies of initiation, and great baths fed by subterranean rivers,
which are still flowing as they did in the days of the Incas.”

“Do you think we shall find such things?” asked Nat, his eyes aglow at
the prospect.

“You mean, do I think we shall find the lost city?” corrected the
professor, with a smile. “Well, Master Nat, I don’t doubt that if we
find the city we shall also find such things. It is rumored that the
lost city we are in search of is in even better preservation than the
famous ruins of Peru itself.”

“I wish you would tell us some more about that sacred dome with all the
gold on it,” said Joe.

“I’ll tell you all I know,” said the professor. “It is believed then,
that the sacred dome was the place where Manco Capac, an Inca deity,
descended to the earth. To this day the natives approach the spot with
the utmost awe and reverence.

“According to their ideas, no bird would alight up, or animal approach
it. All but priests were forbidden to come even within sight of the
rock, although it is hard to know how this could be prevented, as it is
of immense size. At ordinary times its gold plating was covered by a
veil of the finest and most costly materials, and this was never
removed, except on great religious festivals.”

“It must have been a fine sight to see that great golden rock
glittering in the sun,” said Nat thoughtfully.

“It must, indeed,” agreed the professor. “There was also a Temple of
the Moon, and a vast Temple of the Sun, as well as other buildings
whose purposes are veiled in mystery, and must ever be. One thing is
certain, though, human life must have been as cheap as water, for it is
estimated that many thousands of slaves’ lives were sacrificed in
building the city of which only ruins now remain.”

“It reminds one of Egypt,” said Nat.

“So travelers have observed,” rejoined the professor; “after all, the
history of civilization repeats itself.”

“Has much treasure been discovered there?” inquired the practical Joe.

“Quite a good deal, yes,” was the reply; “but the Spaniards took an
immense quantity of it, and to-day there is little left. However, from
time to time a valuable find is made, I am informed.”

“And the city we are in search of—do the same conditions exist there?”
inquired Nat.

“Very probably. According to tradition, the fierce and warlike Indians
kept the Spaniards away from the spot,” was the reply.

“I hope so,” spoke Joe, in whose mind visions of vast treasures and
strange, massive buildings were already rising. As for the others,
perhaps they, too, even the professor, were also weaving castles in
cloudland. At any rate, they were silent for a time, brooding over the
great mystery to whose heart they hoped to penetrate ere long.

But the period of silence was not of lengthy duration. Mr. Tubbs, who
possessed a good tenor voice, volunteered to sing a song.

“Is there anything he can’t do?” thought Nat.

The song he chose was “Old Kentucky Home.” When he came to the chorus
the boys’ voices blended with his in the plaintive cadences of the
music. It was a strange sound to be ringing out in that primeval place,
where perchance the foot of civilized man had never trod before.

But the singing was due to terminate abruptly. Nat, who had been gazing
outside the circle of firelight, caused the breaking off of the concert.

He sprang to his feet and seized up a rifle, calling on the others to
do the same.

“What is it, my boy?” asked the professor, “a wild beast?”

“No—that is, I don’t think so,” rejoined the boy, whose face was rather
pale. “I’m almost certain that what I saw was the figure of a man
crouching over yonder and watching us.”

Exclamations of consternation filled the air.

“Indians!” gasped Ding-dong Bell.

“It may have been nothing but a jaguar or a prowling puma,” said the
professor. “Are you sure your eyes didn’t deceive you?” he inquired of
Nat.

“As I said, there’s a bare chance I might have been mistaken,” rejoined
the lad, “but I don’t think so. However, the instant that I looked, the
figure vanished.”

“It’s very strange,” mused the professor, “and yet it may have been an
Indian, little as I like to think of such a contingency. However, we
will keep a sharp watch to-night, and be prepared to ‘slip our
moorings’ at an instant’s notice.”

All agreed that this would be an excellent plan, and forthwith the
knots on the mooring ropes were retied, so that one tug from those on
board the _Discoverer_ would release the craft and allow her to shoot
upwards. Preparations for what all felt was not likely to prove a
restful night, were then begun.

The first watch was assigned to Mr. Tubbs and Joe, and would last till
midnight. The next one would be assumed by Nat and the professor.
Ding-dong Bell, who was still nervous and rather pale from his
experience of the afternoon, was to be allowed to slumber all through
the night.

He protested loudly against this, demanding to take his share with the
rest; but was obliged to be content with the promise that if any
trouble occurred he would be routed out to assume charge of the engine.
In spite of their apprehensions, Nat and the professor slept as soundly
as Ding-dong. In fact, it did not seem to Nat that he had been asleep
more than a few minutes when Mr. Tubbs aroused him to take his watch.

“All quiet,” was the rubicund-headed one’s response to the professor’s
inquiry.

Hardly were the words out of his mouth before the silence of the night
was broken by an almost unearthly yell.

“What’s that?” cried Nat, considerably startled.

“Nothing but a screaming monkey,” said Mr. Tubbs. “I’ve heard them in
Brazil often.”

“But they don’t cry out at night unless they are disturbed,” said the
professor decidedly.

“You think some one is in the woods?” asked Nat.

“I don’t know about a human being. But the fact that you are almost
certain that you saw a man prowling about last night, makes it look
suspicious.”

“It may be only a panther,” said Mr. Tubbs.

“Possibly. Let us hope that is the case, but in the meantime prepare
for trouble; then, if it comes, we can meet it. Master Joe, rouse out
Master Bell. Nat, I wish you’d bring me that peculiar-looking gun you
were asking me about yesterday when you saw me place it on board.”

The gun referred to was a queer-looking weapon, with a mouth shaped
like an old-fashioned blunderbuss. It had an immense barrel, and
altogether was a very odd-looking weapon. Nat knew where it stood in
the gun-rack and soon fetched it. The professor examined the lock and
appeared to find everything satisfactory.

“What kind of a gun is that?” asked Nat, full of interest.

“I don’t want to say much about it till I see how it works,” said the
professor. “It is the invention of a friend of mine. If we are attacked
it will be a fine opportunity to test it.”

Nat would like to have asked more questions, but at that instant a
chorus of cries and shrieks arose from the woods on every side. The
cries were uttered by roosting birds and monkeys, which had been
disturbed by some cause. What that cause was, the professor soon
guessed.

“It’s the Caripunas,” he whispered; “almost beyond a doubt. Master
Bell, stand by your engines. Tubbs, take up your position at the wheel
and be ready to manipulate the searchlight. Master Nat and Master Joe
will stand ready to slip the tie-ropes when the word is given.”




                             CHAPTER XVIII.

                              WHAT IT DID.


The moments that followed were filled with a tenser excitement than any
of the lads had ever known before. After the first frightened flurry of
the alarmed creatures of the forest, a deep silence prevailed. It
lasted for possibly fifteen minutes, and then the professor decided not
to test their nerves to the breaking point.

“Turn on the searchlight!” came the breathed command.

A sharp click followed, as the light, which was supplied by current
from the storage battery, was switched on.

A dazzling white pencil of light swept all about the _Discoverer_. Its
brilliancy pierced the night like a saber, and illumined the solemn
trees and the open savannah all about.

At almost precisely the same instant, a chorus of ferocious yells and
cries broke out, and from all sides there rushed on the aerial
adventurers a horde of short-statured Indians. The searchlight showed
them to be wild-looking men, clothed in a single garment, their heads
covered with straight black hair. Through their lower lips most of them
had thrust a triangular bit of white stone with a sharp point. This
added to their fantastic appearance.

Nat noted that one of them, larger in stature than the rest, seemed to
be the leader. He also saw, with an unpleasant thrill, that they
carried long blow pipes. It was through these pipes, the professor had
said, that the poisoned arrows were discharged.

Rope in hand, ready to slip at the word of command, Nat stood his
ground. On the opposite side of the framework Joe was likewise waiting.
Neither boy budged an inch, and Ding-dong stood steady as a rock at his
engines.

So suddenly had it all happened, in fact, that neither boy could regard
it for an instant as more than a dream.

Suddenly something struck the metal framework by Nat’s head with a
sharp ping!

It was an arrow, and so close had it come to the lad that he had caught
its whistling sound as it sped past his ear.

“Phew! This is warm work, with a vengeance,” he muttered.

He saw the Indians give a sudden concerted onrush, yelling like maniacs.

“Keep the searchlight in their eyes. It dazzles them!” called the
professor.

Then came another command.

“Let go your ropes!”

Nat and Joe instantly dropped their ropes and seized up rifles.

“Don’t fire!” cried the professor sharply. “We don’t want to injure
them if we can help it.”

The great dirigible swayed for an instant and then began to rise.

“Turn on your power!” shouted the professor.

The bell for “full speed ahead” rang sharply out. At the same instant
the propeller began to whir.

As it did so, several Indians, who, in their onrush on the dirigible,
had clambered upon it, were thrown off in all directions. They rolled
over and over, like so many footballs. This made the others pause an
instant, and in that instant the dirigible rose from the ground.

But the chill night air had condensed the gas, and she rose slowly.
Before more than five feet had been gained in her upward rise, the
Indians recovered from their amazement and charged like a pack of
furies.

“Flat on your faces!” shouted the professor, as a shower of arrows
pinged and pattered in the framework of the craft.

They obeyed the command, and then Nat saw the queer gun brought into
use. The professor raised it to his shoulder and pulled the trigger.

Instantly a stream of colored balls, like those that issue from a Roman
candle, poured from the bell-like muzzle. But almost simultaneously
with their discharge, they burst with sharp reports, and the whole air
became impregnated with a black, all-obscuring smoke as thick as a
London fog.

The dense clouds spread on every side, completely obscuring the
dirigible from the view of the Indians below. Higher and higher she
rose, while below her the dense smoke veiled everything like a curtain.
Nat caught a whiff of the vapor, and it made him cough and choke.

“I’ll bet those Indians aren’t enjoying it,” he thought to himself. “So
that was what that queer gun was.”

In a few moments they were high above the tree-tops, and the professor
ordered the lights turned on. A switch was pushed over by Mr. Tubbs in
the pilot-house, and the _Discoverer_ blazed out with incandescents
like an illuminated battleship. For a few seconds nothing much was done
but to exchange congratulations. No one was hurt, and not an arrow had
pierced the gas bag. This was accounted for by the fact that the
Indians, not understanding how vulnerable that part of the craft was,
had confined their volleys to the occupants of the lower structure.

“A most fortunate escape,” declared the professor, but suddenly he
clapped his hand to his head.

“My hat!” he cried wildly, “I’ve lost another hat.”

“Here it is!” cried Joe, picking up the article of headgear.

He held it up, transfixed by an arrow. The missile had penetrated it
and whisked it from the professor’s head without touching him.

“I wouldn’t have lost that for worlds,” said the professor, thanking
Joe, and removing the arrow very gingerly.

“One scratch from that arrow would result in death,” he said, in
explanation of his extreme care.

He held it out for the boys’ inspection. It had a stone head,
discolored by some whitish matter at the tip. The shank of it was about
two feet long, with some sort of cloth wrapped around the end to make
it fit the blowpipe tightly.

“What kind of poison do they use?” asked Joe.

“An infusion of the St. Ignatius plant, from the beans of which
strychnine, our deadliest narcotic, is obtained,” was the response.

“We’d better make a thorough search for any other arrows,” suggested
Nat.

“I think so,” agreed the professor; “they are not the sort of things to
have lying about.”

A search of the _Discoverer’s_ lower structure resulted in the finding
of a dozen or more of the deadly missiles. These were all thrown off
into the air at once.

“And now,” said the professor, planting his hat firmly on his head, “I
suppose you are anxious to know something about that queer gun I used.”

A chorus of assent greeted this remark.

“Well, it’s a weapon called the Fog-maker, and was invented by a friend
of mine especially for use in aerial warfare, or for protecting a small
vessel from hostile aeroplanes,” said the professor. “As you saw, it
works perfectly, throwing out a thick cloud of dark, acrid smoke, which
is heavier than the atmosphere. While it has no permanent bad results,
yet it renders those who breathe it insensible for a time.”

“It is indeed an effective weapon,” declared Nat; “can we see one of
the projectiles?”

The professor took up the gun and slid open a small space in the stock.
Then, pressing a metal button, he caused two round black objects, about
the size of small oranges, to roll out into his hand.

“The magazine holds ten of these,” he said. “They are made of glass and
filled with chemicals.”

“What kind of chemicals?” asked Joe.

“Ah! That is the secret of the inventor,” was the reply, “nobody but he
himself knows what they contain; but that they are effective, you must
admit. He told me that the old ‘stink-pots’ that Chinese pirates used
to use gave him the idea. If ever there is a war in the air, I think
that the nation equipped with this invention will have a powerful
implement of havoc.”

“I should think so,” said Nat; “one whiff of it was quite enough for
me.”

All this time, by the professor’s directions, the dirigible had been
swung in wide circles at an altitude of about fifteen hundred feet. So
interested had they all been in the professor’s description of the
novel aeroplane gun, and in the other matters that had occupied their
attention, that the big air cruiser had not yet been “tidied up.”

This was the next task to demand their attention. Joe set to work to
hoist up and coil the rope which had been cast loose when the hasty
ascent was made. But he hadn’t given it more than a couple of tugs
before he uttered a shout that brought the others, except Mr. Tubbs,
who was at the helm, running along the substructure to his side.

“What’s up now?” demanded Nat.

“Why, either this rope has caught in something below, or there’s
something heavy attached to it,” was the astonishing response.

“Impossible for it to have caught,” declared the professor, “we are now
fifteen hundred feet or more above the surface of the earth, and the
rope is not more than a hundred feet long, at the most.”

“Well, feel it yourself,” responded Joe.

Nat gave the rope a tug. As Joe had said, there was clearly something
heavy attached to the end of it. But what could it be?

“We’ll soon see,” said the professor. “Master Joe, attach another
length of rope to it, and then have Master Bell switch power on the
electric winch.”

This was done, and the powerful winch began to revolve, winding the
rope on its barrel. As the rope began to grow shorter, the boys peered
over the edge of the substructure in an effort to make out what could
be at the end of it. The glow of light spread by the illuminated craft
soon showed them.

“It’s a man!” shouted Nat in a thunderstruck voice, as the figure of a
human being, clinging desperately to the rope, was brought into view.




                              CHAPTER XIX.

                       AN INVOLUNTARY PASSENGER.


“A man!” exclaimed the amazed professor. “Why, how in the world did he
come here?”

“I don’t know,” said Nat; “but there he is.”

“He must have caught the rope when the _Discoverer_ shot upward,”
suggested Joe. “Maybe he thought he could stop us.”

“He’s all wer-wer-wound up in the rope,” announced Ding-dong, who had
been peering over the side during this dialogue. “His eyes are closed,
and he seems half-dead from fright.”

“Let us drag him on board at once,” said the professor.

The boys lay flat, while the winch was started up until the man’s head
was on a level with the under part of the substructure. Then three
pairs of strong young arms reached down and dragged their involuntary
passenger over the side.

“He’s an Indian!” cried Joe, as the man being dragged into safety from
his precarious position proved to be a squat, black-haired little brown
man, clad in a garment of rough fibre, and with one of the peculiar
ornaments Nat had already noticed, thrust through his under lip.

All this time the Indian had kept his eyes tight closed, and had not
uttered a word. Now, however, he opened his eyes, and threw himself
down flat on his face on the _Discoverer’s_ deck. There he groveled in
an attitude of the most complete humility.

“He thinks we are sky gods, or demons of some sort,” declared the
professor, reading the man’s consternation aright.

“I don’t much blame him,” said Nat, with a smile, “that ride through
the air at the end of the rope must have been the most terrifying
experience of his young life.”

“Young life,” scoffed Joe, “he must be sixty at least.”

“Well, that is young sometimes,” said the professor, who owned to that
age himself, although he was as active as most men half his age.

Suddenly the Indian began to speak, but without raising his head. He
poured out a flood of words. For an instant, they thought he was
speaking his native dialect, but all at once the professor understood.

“He’s talking Spanish,” he said, “and imploring us to spare his life.
Just as I thought, he thinks we are beings from another world.”

“Well, if I were in his fix I’d be inclined to think so myself,” said
Joe.

But the professor began putting rapid questions, at the same time
raising the man’s head and showing him by signs that they meant no harm
to him. Little by little the Indian seemed to recover his courage. But
he was sorely shaken by his adventure, and explained that when the
ropes began to drag over the ground he had seized them to stop the
dirigible, and had become entangled in them.

“Why did your tribe attack us?” asked the professor.

“We thought you were human beings,” was the response. “But now we know
otherwise.”

He would have cast himself on his face again, but the professor raised
him and spoke encouragingly to him.

“Maybe if you’d give him something to eat he’d feel better,” suggested
Joe, practically.

“That might be a good idea, and it will show him that we mean him no
harm,” said the professor.

The Indian, who said his name was Matco, was taken to the cabin, the
sight of which, with its comfortable furnishings and strange scientific
instruments, filled him with fresh terror. But little by little he
regained his self-possession to a degree, and ate what he was given
with zest.

The crew of the _Discoverer_ joined him at the meal, of which they
stood in need, Joe relieving Mr. Tubbs at the helm. The stout lad had
taken a few lessons in steering before from Mr. Tubbs, and found that
it was not as difficult as he had supposed it would be. But then, Joe
had had plenty of experience at the wheels of both automobiles and
boats.

But after all, the selection of a green hand at the wheel proved
somewhat disastrous. The sun arose while they were still talking to the
Indian, and Mr. Tubbs was hearing details of the strange manner in
which the man had boarded the airship.

In that rarefied air the rays of the luminary of day soon warm the air,
and, as a consequence, the gas within the _Discoverer’s_ bag began to
expand very rapidly. Those in the cabin, of course, did not notice that
the craft was rising rapidly, and Joe did not give a glance at the
barograph, it not occurring to him to do so.

All at once he gazed over the front of the pilot-house and looked down
below. What he saw almost made him utter a cry. The _Discoverer_ was at
a tremendous height, and appeared to be rising more and more rapidly.

Joe, in a sudden panic, twitched a lever, and the next instant the
craft shot skyward at breathtaking speed. The boy had set the wrong
lever and had adjusted the planes to a rising angle.

Before the professor, who had felt the craft rear upward, could reach
the pilot-house, the dirigible had shot up five hundred feet or more.
Behind the professor came the others, except Matco, who was sent into a
fresh paroxysm of fright by the strange and sudden upward leap of the
airship.

“Good heavens!” cried the professor, as he jerked over the descending
lever, “we have risen to a height of more than eight thousand feet.”

As he spoke they suddenly noticed that the air had grown bitterly chill.

“Just like Joe to make a break like that,” said Nat, with a
good-natured laugh that took the sting out of his speech; “we’d better
get down to earth once more as quickly as possible. It’s too cold to be
comfortable up here.”

“We’ll soon drop now,” said Mr. Tubbs confidently.

But as the minutes passed and it grew colder, his face became grave.

“We’re rising,” cried the professor, glancing at the barograph.

“That’s right,” cried Nat. “What can be the matter?”

“Have you got the descending planes set at their sharpest angle?”
demanded the professor.

“Yes,” was the response, “but they seem to have no effect on her at
all.”

The professor thought a moment.

“We shall have to pull the escape valve and let out some gas,” he said.
“The rising sun has warmed the air till the expansion of gas has made
the bag too buoyant for the planes to have any effect on it.”

“Won’t that waste the gas?” asked Joe.

“Yes, but we will have to do it. Mr. Tubbs, pull the escape valve,
please,” said the professor, whose nose was red and whose teeth were
beginning to chatter.

“It’s snowing!” cried Nat suddenly.

The air was filled with flying flakes, and the _Discoverer_ seemed to
be soaring through a wonderful white void. But it was no time for
admiring such effects.

Reaching above his head, Mr. Tubbs gave the cord that worked the escape
valve situated on the top of the big bag, a sharp tug.

Then he gave it another and another, with no results.

“It’s stuck fast!” he said, the words coming out shrilly from his blue,
frozen lips.

A look of dismay spread over the professor’s face.

“Nonsense,” he said. “It can’t be.”

“But it is, I tell you.”

“Let me try it.”

The professor gave a hard tug, but still the cord did not budge.

“Give me a hand here,” he said to Nat, and together they tugged.

Suddenly, and without the least warning, the cord broke off short in
their hands, and they fell sprawling on the floor. To his astonishment,
when Nat tried to rise, he found the task difficult. Breathing seemed
to be a labor, and his limbs felt like lead. The professor had actually
to be helped to his feet, and then staggered, with one hand over his
heart, to the helmsman’s settee, on which he sank, breathing with a
queer, whistling sound.

“What on earth has happened?” demanded Joe, who like the others, felt
strangely oppressed and heavy. His head ached as if it would burst.

“The—the cord must have frozen to the sides of the bag,” gasped out the
professor. “The change to this awful altitude turned the night moisture
accumulated on the gas bag’s sides to ice. I fear we are doomed,
unless——”

He paused, panting and gasping.

“Unless what?” demanded Nat, forcing the words out.

“Unless we can get that valve open.”

“And if we can’t?”

“Then we must drift higher and higher till we perish of cold, or the
bag explodes and we are precipitated to the earth.”




                              CHAPTER XX.

                     “ALL OUR LIVES DEPEND ON IT.”


Nat staggered toward the door of the pilot-house. Mr. Tubbs, at the
wheel, the least affected of the adventurers, turned his head.

“What are you doing to do?” he demanded.

“Get that valve open,” was the brief reply.

“Boy, you are crazy!”

“Maybe, but I’m going to make a try for it, anyhow. All our lives
depend upon it.”

“By hooky, if it’s to be done, you’ll do it, and if not, why then, I
guess we’ll have to meet death as bravely as we can,” was Mr. Tubbs’
muttered remark, as Nat plunged out of the door.

In the cabin Ding-dong, breathing hard, lay on a narrow bunk. Matco was
stretched on the floor, apparently unconscious. Nat gazed at them half
stupidly.

“Pretty far gone,” was the thought that came into his dazed mind. Then
he plunged on again, reeling as he went, his mind concentrated with
bitter intensity on the task that lay before him. Gaining the deck, he
found the cold almost too much for him, and he turned back for an
instant and donned warmer clothing from the professor’s chest.

Then he doggedly proceeded with his self-imposed task. He noticed that
the engine had stopped. The bitter cold had condensed the moisture
within it and frozen the lubricating oil.

But Nat wasted no time on these observations. What he had to do must be
done quickly if at all.

Gazing upward at the huge bulging curve of the under side of the gas
bag, he saw the broken ends of the valve cord fluttering from the bag.
They were far above his reach, even if the securing of them would have
done him any good.

It was only for an instant that he paused. Then, summoning up every
ounce of resolution in his determined mind, he seized hold of the
starboard rigging and began clambering up and outward.

------------------------------------------------------------------------

[Illustration: Nat climbed by sheer force of will power.]

------------------------------------------------------------------------

He did not dare to look down into the awful void beneath him—vast and
empty as eternity itself. Keeping his eyes steadily fixed on the
bulging bag, Nat climbed by sheer force of will power till he was up to
the network that encased the bag.

Right here began the most difficult and terrifying part of his task.
Hanging desperately above the immensity beneath him, he had to make his
way to the upper part of the bag. He did not dare to think of what he
was doing. The very notion of it made him feel sick and dizzy. The lad
just climbed, fixing his mind on the thought of reaching and opening
the valve.

Somehow—to this day Nat couldn’t tell you how—he clambered round under
the bulge of the bag and began the easier task of making his way up the
tightly rounded sides to the top of the great cylindrical gas
container. As the professor had surmised, ice had formed on the outside
of the bag, and made Nat’s endeavor ten times more hazardous and
difficult. This ice had clogged the valve ropes, and Nat saw that the
only thing to do was, as he had made up his mind, to climb on till he
reached the top of the bag.

The possibilities of a slip were awful, and Nat no more dared think
about them than he had about the chances of his slipping when he was
hanging between earth and sky under the lower part of the bag. He
resolutely dismissed them from his mind.

But the physical difficulties of the lad’s self-imposed task were
almost overwhelming. There was a sharp pain in his chest, and his limbs
felt as if they had leaden weights attached to them. Suddenly a warm
stream of something Nat knew to be blood, gushed from his nose; but
still he worked his way upward, climbing amidst the network meshes like
a sailor on ratlines.

Once or twice he was compelled to pause from sheer exhaustion, and,
clinging on with might and main, to spread himself flat on the surface
of the gas bag to rest.

If Nat had not been a clean-lived lad all his life, and had not been a
hater of smoking and bad company, he would never have been able to
endure this ordeal; but somehow, his young vitality won out, and at
last he could reach out a hand and touch the valve.

Bracing himself against the rigging, he tugged with all his might. But
the condensed moisture had formed ice on the valve, and it stuck.

Nat felt a childish rage take possession of him. Raising his fists, he
beat and tore at the valve, while tears of physical weakness and
exhaustion streamed down his cheeks.

“I will get you open! I will! I will!” he cried again and again.

But even his frame gave way at last, and suddenly his eyes grew dim and
he felt as if a sword had been plunged through and through him.

As everything grew black, Nat, with a last effort of consciousness,
clutched at something to save himself from being plunged backward into
space.

He caught it, or thought he did, and then his senses went out from him
with a vivid flash and a terrible roaring in his ears like the sound of
a hundred waterfalls.

                  *       *       *       *       *

Half an hour later, or at ten o’clock, Joe Hartley opened his eyes. At
first he hardly knew what had befallen him; but in a few seconds his
recollection came back with a rush. He remembered that the _Discoverer_
had seemed doomed, recalled Nat’s plunge through the door and how he
had tried to follow his chum, but had fallen, overcome by exhaustion,
at the door.

But now all the chill was out of the air, bright sunlight streamed
through the pilot-house ports, and the professor and Mr. Tubbs, both of
whom had collapsed on the floor, were sitting up looking about them
rather bewilderedly. The professor was the first to speak.

“A miracle has happened,” he declared. “The _Discoverer_ is out of
danger.”

“The barograph shows twenty-five hundred feet,” announced Joe, who had
been studying that instrument.

“Where are the others?” asked Mr. Tubbs, rising rather weakly to his
feet.

As if in answer to his question, Ding-dong Bell appeared in the doorway
between the pilot-house and the main cabin.

“Where’s Nat?” he demanded.

“Isn’t he out there with you?” asked Joe, with a quick leap of his
heart.

“No. The only person out there is Matco. He’s so scared that he’s under
the ber-ber-bunk.”

“Where is the lad?” demanded the professor earnestly, with a note of
anxiety in his voice.

Mr. Tubbs, who had been struggling with his dim memory of events
preceding his collapse, spoke:

“I recall it now,” he said. “Nat said he was going to get that valve
open”—he paused—“somehow.”

“And you let him go?” demanded the professor.

“I—I didn’t mean to,” stammered the repentant Mr. Tubbs, “but I was so
nearly on the verge of caving in, that I couldn’t carry out my resolve.”

“Search the craft thoroughly,” ordered the professor, lines of anxiety
showing in his face, “there was only one way to open that valve.”

They looked their questions.

“And that was by climbing around the gas bag and opening it by hand.”

“Good gracious!” exclaimed Joe. “And Nat dared do such a thing!”

“He must have, and succeeded, too,” said the professor in a curiously
tense voice, “the opening of that valve was the only thing that would
result in our having dropped to a supportable region of the air.”

“But we are dropping no longer.”

The exclamation came from Mr. Tubbs.

“No. The automatic cut-off arrangement would have closed the valve when
we had reached a warmer belt of atmosphere,” explained the professor,
“but don’t let us lose time talking here. Scatter through the
_Discoverer_ and make a thorough search. He may have dropped
unconscious somewhere.”

The anxiety with which the search was conducted may be imagined. The
_Discoverer_ was allowed to drift lazily along while they sought some
trace of the missing lad, but the search resulted in nothing.

“There is only one conclusion to be reached,” said the professor in a
solemn voice, “poor Nat paid the penalty of his bravery with his life.
He——”

The man of science broke off, unable to command his voice, and at the
same instant came a cry from above them—a hail from out of the air, it
seemed:

“Hello, people!”

“Good heavens! It’s Nat!” fairly shouted the professor, as Nat, whose
feet were alone visible round the bulge of the gas bag, clambered
nimbly down and dropped from the rigging, beside them.

In his excess of joy, the professor flung his arms around Nat’s neck,
much to the lad’s embarrassment, while the rest fairly fought for a
chance to grasp his hand. In intervals of joy making, Nat told his
story, part of which we are familiar with.

It seemed that when he swooned on the swaying balloon top he
instinctively clutched at the first thing his hand encountered, which
was one of the valve ropes. The valve, already loosened by his pounding
on it, yielded to the sudden pressure upon it and jerked open. At
least, this was the only explanation Nat could furnish of the fortunate
occurrence.

When he came to himself he said he saw that the _Discoverer_ was at a
reasonable height, and manipulating the cords he again closed the
valve. He was too weak to attempt the descent at once, but lay
outstretched on the top of the gas bag, regaining his strength. All
this time he suffered with a dreadful fear that his friends below might
have succumbed to the awful rigors of the upper air. With an
apprehensive heart he at last began the climb down and he concluded:

“You may imagine how delighted I was to hear your voices, even if the
professor was preaching my funeral sermon.”

The boys broke out into wild yells of enthusiasm.

“Three cheers for Nat Trevor, the bravest boy on earth!” shouted Joe
Hartley.

The shouts rang out oddly in the thin atmosphere of mid-air, but they
relieved the boys’ feelings. As they died out, Matco appeared at the
door of the cabin, and gazed at the scene a moment. Then seeing that
Nat was the idol of the moment the Indian ran nimbly along the swaying
deck and throwing himself on his knees, placed Nat’s foot on his head.

It was the last straw.

“Say, fellows!” cried Nat with a red face, “that’s about all of this
hero business. Let’s have some breakfast and get the engine going.”

And so, what might have been a tragedy, ended in one of the merriest
meals ever enjoyed by aerial travelers.

By noon the _Discoverer_, none the worse for her involuntary flight
into the icy realms of space, was able to resume her voyage over the
desolate peaks and abysses of unknown depths, above which the
adventurers were now soaring.




                              CHAPTER XXI.

                        “FEATHERED AEROPLANES.”


The professor’s observations that day showed that they were within two
hundred miles of where the fabled city ought to lie, always supposing
that it really had an existence. But you may be sure that not one of
the Motor Rangers doubted that fact.

The course was altered, and the _Discoverer’s_ bow turned toward some
ragged-looking peaks that cut the sky line to the northwest. The
country over which they were now passing was, as has been said,
desolate in the extreme. It appeared to have been devastated by
earthquakes or forest fires, and the vegetation was scanty, while the
surface of the ground was split, and scarred and hillocked like a
crumpled bit of parchment. But toward afternoon the character of the
scenery changed. The mountains grew in gloomy grandeur and were clothed
with dense tropical growth. Between the great masses and lofty
elevations lay dark and unfathomable chasms, at whose depth only a
guess could be made. It was wild and dismal scenery, and, viewed even
from above, oppressed the travelers with its sense of lonely vastness.

The _Discoverer_ was not making as good time as usual, owing to a stiff
headwind. Then, too, the engine had not developed its full power since
its freezing up in the upper aerial regions. But the professor
announced himself as well satisfied with their progress. Matco
gradually got over his first fear of the air travelers and talked to
the professor in his rough Spanish, which Nat could hardly understand,
so besprinkled was it with mispronunciations and Indian words.

The old Indian was much interested in trying to find out what the white
men,—for he no longer thought them gods,—were doing in that part of the
country. But the professor deemed it wisest not to tell him. Ultimately
they would have to set him free, and if he knew too much of their
expedition he might make trouble for them with the other Indians.

It was the middle of the afternoon, and Nat was seated in the cabin
reading a book on the Incas, when a hail from the pilot house brought
him to his feet. Joe, who was at the wheel, was calling him.

“Nat! Nat! Come out here—quick!”

Nat lost no time in obeying. As he joined Joe the latter excitedly
pointed ahead of the _Discoverer’s_ bow.

“Look at those birds, Nat; they are the largest I have ever seen. I
wonder what they can be?”

The birds referred to were flying and wheeling in great circles above a
ravine some distance off, but far off as they were, it was easy to see
that they were of immense size.

“They are bigger than the biggest turkey buzzard I ever saw in
California,” said Nat, gazing at them. “Let’s have a look through the
field glasses.”

He took the instruments out of their box near the helmsman’s wheel and
applied them to his eyes.

“Why, they look like small aeroplanes!” he exclaimed in astonishment.
“Their wing spread must be ten or twelve feet, judging from here.”

“How many of them are there, anyhow?” demanded Joe.

“Easily fifty, I should say. Maybe more. It would be impossible to
count them accurately.”

“They are right on our course,” said Joe, glancing at the compass, “so
that we shall soon have a close view of them.”

“I’ll go and rouse the professor. He’s taking a nap; but I know he’d
like to see such a sight.”

And Nat hastened off on his errand.

By the time he returned with the professor, the _Discoverer_ was much
closer to the giant birds. The man of science scrutinized them through
the glasses.

“Condors,” he announced. “This is most interesting. These birds are the
largest birds of prey in existence. Humboldt, the famous traveler, said
that Indians told him that they had been found measuring eighteen feet
from wing tip to wing tip.”

“Well, I should say they _are_ aeroplanes,” exclaimed Nat. “Do they
ever attack men?”

“Cases of it are not unknown,” said the professor, “and almost every
Andean village has a story about a condor flying off with a baby. As a
matter of fact, though, I guess they confine their attentions mostly to
young sheep or calves light enough for them to carry.”

As they drew closer to the soaring mass of birds, they could see that
if they were interested in the birds, the birds were quite as much
interested in them. One or two began making long, wheeling arcs that
brought them closer to the _Discoverer_.

“I guess they are wondering what sort of a bird we are, anyhow,”
laughed Nat.

Indeed, it seemed so. Almost imperceptibly the birds gathered about the
_Discoverer_, wheeling and screaming all about the craft. It could now
be seen that they had sharp, large, hooked beaks, and a ruffle of dark
flesh at the bottom of a flabby neck. Their wings were of a dull gray
color, with black tip feathers, and were of a sweep and size undreamed
of hitherto by the boys.

“They look like the harpies we used to read about in school,” said Joe.

“They do, indeed,” said the professor. “One could readily imagine such
creatures tearing unfortunate human beings to pieces.”

“They don’t seem afraid of us, anyhow,” said Nat suddenly, as one of
the great condors swept by quite close to the _Discoverer_ and uttered
a wild scream that sounded like a cry of defiance.

“No, they don’t. I—— Bless my soul, they are attacking us!” cried the
professor as two or three of the birds flew at the gas bag with beak
and claw.

------------------------------------------------------------------------

[Illustration: “Now, boys,” spoke the professor, “we must use our best
marksmanship on these creatures.”]

------------------------------------------------------------------------

“Get out the rifles, quick!” cried Nat. “They’ll tear the bag open if
they keep that up.”

“They will, indeed!” said the professor apprehensively. “Shoo!”

But he might as well have said “Shoo!” to a tiger as to the giant birds
of prey that now surrounded the _Discoverer_ on every side. Angry
screams and the rushing noise of huge wings filled the air.

Nat returned with the rifles, and with Ding-dong Bell, who had already,
from his post at the engines, observed the great birds.

“Now, boys,” spoke the professor, “we must use our best marksmanship on
these creatures. They are a real menace to the ship.”

Nat took up his position at one side of the pilot house, Ding-dong Bell
at the other, while the professor aimed from the centre window.

At the word “fire!” from the professor, all three rifles began to pump
lead into the wheeling, circling, screaming flight of condors.

Several stopped abruptly in their soaring circles and fell to the
earth, stricken to death. But others, that were only wounded, fought
with more fury than ever. The attack by the adventurers appeared to
enrage them. They flew furiously at the _Discoverer_, and one or two
even dashed themselves at the pilot house.

But after ten minutes or more of steady firing their numbers
diminished. The ones that were left began to sheer off, and finally
took flight away from the invaders of their realm. The noise of the
firing brought Mr. Tubbs and Matco out of the cabin, and both watched
with interest the effects of the fusillade.

When it was over, and the _Discoverer_ had left the last of the great
birds behind, old Matco spoke excitedly in Spanish to the professor.

“What does he say?” asked Nat, when the old man had finished what
appeared to be a tirade against something or somebody.

“He says,” rejoined the professor, “that what we have done is very
good. That when he was a youngster he was carried off by one of these
birds. His mother, who rushed out to save him, was attacked by the
condor’s mate and so seriously maimed and torn that she died.”

“But how did he escape?”

“His father shot the bird that was carrying him off, with one of the
poison arrow tubes,” rejoined the professor, “both the bird and the
infant fell to the earth, and Matco says that is the reason his leg is
so twisted and that he walks with a limp.”

The boys found this very interesting. It explained, too, something that
they had noticed before, and that was that old Matco walked with a
decided limp.

“Tell us something more about the condor, professor,” suggested Nat.

“As I think I said,” rejoined the professor, “it is one of the vulture
family, and is found from the Isthmus of Panama clear down to the
Straits of Magellan. They usually live in the mountains, but sometimes
they come down to the seashore to pick the flesh of dead whales. In
fact, they have a preference for dead or decaying flesh.”

“Just like turkey buzzards,” said Joe.

“They are a first cousin of that bird,” said the professor. “A friend
of mine, who had been a great traveler in South America, told me once
that the Indians will catch them for two dollars each, and that
sometimes they do quite a lively trade.”

“I shouldn’t much care to have one for a pet,” spoke Joe; “but how do
they manage to get hold of such immense birds?”

“By a very simple and ingenious method. They build a pen around the
carcass of the first dead steer they can find on some cattle estancia,
and then await the arrival of the condors to feast on the flesh.

“The condor, when he is gorged, cannot rise without taking a run——”

“Just like an aeroplane in that, too,” commented Nat.

“That is true,” said the professor. “Well, as I was saying, the bird
cannot rise without this preliminary run, and, of course, the picket
fence interferes with this. That is the condor catcher’s opportunity.
He throws a lasso around the bird he has selected and lets the condor
fight till he is exhausted. Then he throws another and another till Mr.
Condor is tired out. That done, the bird is placed in a rough cage and
conveyed to the customer.”

“That’s a lo-lo-lot of work for t-t-t-two d-d-d-dollars,” stuttered
Ding-dong Bell.

“Any kind of work would be hard for you,” grinned Joe, which almost
precipitated a fight. Nat checked it.

“Don’t roll overboard on this craft,” he said, “even if there aren’t
any sharks about.”

“Humph! I don’t know that they are much worse than those condors,” was
Joe’s comment.

As for Mr. Tubbs he heaved a sigh.

“If only I’d got a moving picture of that fight with the condors,” he
said regretfully.




                             CHAPTER XXII.

                          A SERIOUS ACCIDENT.


Shortly after the battle with the condors, the professor announced
that, inasmuch as they were passing above a favorable landing place, he
intended to make a landing. The spot selected was an open space beside
a fairly large river, the glint of which could be plainly seen like a
glittering ribbon beneath them.

Preparations for a landing were at once begun, and the _Discoverer_
commenced nestling down toward the earth. The professor announced that
the first task of the evening would be to replenish the supply of gas
in the bag from the hydrogen tanks.

The anchorage was made without a hitch, and the _Discoverer_ moored as
securely as before; but in view of their experience of the night
before, the travelers decided to have everything ready to “slip and
run” in case the unpleasant experience was repeated.

As soon as the dirigible was secured, the task of adding to her
depleted gas supply was begun. Two of the cylinders were dragged from
their resting place and deposited on the ground, while the filling tube
was made ready.

The _Discoverer_ was anchored almost on the banks of the stream, a
rapid one, with a rocky bottom and steep banks. While the others were
working about the _Discoverer_, Ding-dong Bell set himself to examining
the gas cylinders.

They were about ten feet long and very slender in proportion to their
length. They were heavy, too, as the tremendous pressure within them
made it necessary to construct them of the thickest and strongest
steel,—the very finest grade obtainable, in fact.

Ding-dong, with his natural curiosity, started lifting one, and found
that to raise one end was all he could manage, and that only by dint of
puffing and blowing.

Joe Hartley, looking around from his work on the filling tube at which
he was assisting Nat and the professor, noticed what his chum was up to.

“Say, put that down! You’re not strong enough to lift it,” he jeered.
“Those things aren’t for kids to monkey with.”

“They’re not, eh?” puffed Ding-dong valiantly, “I’ll soon show you.”

With a supreme effort he managed to raise the cylinder and move it a
short distance.

“Here, stop that!” shouted the professor as he espied what the boy was
doing. “Don’t you know those things are dangerous unless handled
carefully? They’ll go off like a bomb under a sudden shock.”

“That one must have got a sudden shock when it saw Ding-dong,” scoffed
Joe. “Most people do.”

It was too much for Ding-dong. He set down the cylinder and made a jump
toward his tormentor. In doing so, his foot struck the cylinder which,
as it happened, was only just balanced on the steepish slope leading
down to the precipitous river bank.

The gas container began rolling downward. The professor gave a shout.

“Stop it! Stop it! Don’t let it fall over the river bank or——”

Before he could complete the sentence, Ding-dong was valiantly off
after the rolling cylinder. He grasped it, but its weight and the
velocity it had attained, caused it to evade him, and while he fell
sprawling in an effort to regain his balance, the cylinder bounded on
toward the brink of the steep river bank.

“Down on your faces! Down on your faces! Everybody!” fairly roared the
professor.

They all obeyed blindly, not sensing the utility of the order, but
realizing its urgency in the tones of the professor’s voice.

The cylinder gave a leap as it struck a stone, and then bounded over
the edge of the river bank.

Bo-oo-oo-oo-m!

An explosion that shook the ground followed almost instantly. From the
bed of the river a geyser of mud and water and rocks spouted up,
showering everything for a radius of several yards. The explosion the
professor had dreaded had taken place; but, by a miracle, no one was
hurt. No doubt the fact that the detonation took place below the river
bank accounted for this fact.

But the lecture that Ding-dong received! And he admitted that he
deserved it.

“If you ever catch me mo-mo-monkeying with that h-h-high-diddle-diddle
g-g-g-gas again you can ber-ber-ber-blow me up with it,” he declared.

“That ‘high-diddle-diddle gas,’ as you call it, is much too precious
for that,” said the professor with a laugh he could not restrain, “but
I shall adopt other measures.”

The boys had a good opportunity then to see the destructive force
stored in one of those innocent-looking cylinders. Peering over the
river bank they could see that a great hole had been blown in its bed,
and rocks riven and split in every direction.

“It’s as explosive as dynamite,” exclaimed Nat.

“It is, indeed,” said the professor. “The condition of that river bed
gives mute evidence of that.”

“Just think what would happen if a spark should ever enter that gas bag
of ours,” said Nat, with a slight shudder.

“We wouldn’t be able to think,” said Joe succinctly.

“Come, let us get back to work,” suggested the professor, “roll that
gas cylinder closer to the filler tube and we will make the
connections.”

Gingerly enough, as you may imagine, the lads rolled the cylinder
toward the end of the filler tube, which now lay extended on the
ground. The end of the tube was fitted with a union, which, in turn,
was screwed on to the nozzle of the gas cylinder. Then the professor
turned on the vapor, of whose power they had just had such a striking
example.

With a hiss and a roar the gas poured through the filler tube into the
bag, and several small wrinkles, which had developed in its upper
surface, began to fill out. Two cylinders were emptied before the
professor and Mr. Tubbs announced that the bag was full enough.

The evening passed off quietly. As before, the evening meal was eaten
on the ground, and the adventurers utilized the cabin of the
_Discoverer_ for sleeping quarters. Old Matco, the Indian, shared the
meal, but refused to sleep within the cabin. Instead, he rolled himself
up outside, on the substructure, like an animal of some sort. He had
the true aborigine’s dislike of sleeping under a roof. It savored to
him of a trap possibly.

The old fellow, now that he had become used to aerial navigation, did
not seem to object to it in the slightest. He rather appeared to like
it, in fact, and took a childish delight in watching the various
operations that went on on board. It appeared that he had no intention
of detaching himself from the party as yet, and indeed, seemed to have
the liveliest gratitude to them for rescuing him from his unpleasant
position at the end of the swinging rope.

The professor was of the opinion that Mateo might prove useful to them,
so no move was made to urge him to return to his tribe. Indeed, they
were now in the country of another tribe of Indians altogether,—so
Matco informed them,—a tribe as warlike and resentful of the intrusion
of white men as his own. This was not encouraging news, but the
adventurers resolved to make the best of it, and guard against
surprises by keeping a good watch.

Nothing occurred during the first part of the night, and when Ding-dong
and Joe came on duty at midnight the professor and Nat had nothing to
report.

“Don’t forget that time you shot at the mule,” warned Nat, addressing
himself to Ding-dong.

“Oh, no danger of my doing that again,” Ding-dong assured him;
“b-b-b-b-besides, they d-d-don’t have mules in this p-p-part of the
country.”

“That’s good logic, at all events,” laughed the professor, who had
heard the story of how Ding-dong shot at a mule in mistake for an
Indian the night the Motor Rangers camped in the petrified forest in
the Sierras.

Ding-dong and Joe marched up and down for some time, without anything
occurring to mar the quiet of the night. But on what was, perhaps, the
stuttering lad’s twentieth parade around the dirigible, he heard a
queer, inexplicable sort of noise coming from the river.

“Indians,” was his first thought. But then:

“That sounds like somebody snoring, and Indians who were coming to
attack us wouldn’t announce their presence like that,” thought
Ding-dong.

The snoring noise continued. Joe was on the other side of the
dirigible, while Ding-dong was on the river end of it.

“It’s a good chance to distinguish myself,” thought the lad, “after the
mess I made of that gas cylinder this afternoon. I’ll just creep down
there and see what on earth that racket is.”

He began tiptoeing softly toward the river bank, while the grunting,
snoring sound still continued.

“I do believe it’s some one asleep down there,” exclaimed the lad to
himself. “Maybe I’ll make a prisoner and get even on Joe for laughing
at me.”

His mind full of these visions of glory, Ding-dong at last reached the
river bank. Behind him he could hear Joe softly calling, but he made no
answer.

“I’m going to investigate this thing alone,” he said to himself.

Lying flat on his stomach Ding-dong peered cautiously over the bank. He
could see the gleam of the water about ten feet below him and—what was
that? Two dark figures, that appeared to have bulk of considerable
size, moving about in the water? One was larger than the other, and it
didn’t take the boy long to make out that whatever the mysterious
objects were, they were not human beings.

“Wonder if they’re panthers?” thought the boy with a sudden chill. But
then he recollected that panthers are not in the habit of prowling
about in the river bottom.

“And I never heard of a panther grunting,” considered Ding-dong, “I
guess I’ll just——”

But what Ding-dong had “just” made up his mind to do was never
revealed. The bank at the point where he had been leaning over, was cut
out beneath by the action of the river, and in scrutinizing the dark
objects he had leaned rather far over.

Suddenly the bank caved in, and amidst a shower of gravel, rocks and
small bushes, Ding-dong went rolling down into the river.

Splash!

He landed in a deep pool, which, luckily for him, was of sufficient
depth for him to avoid injuring himself. Still clutching his rifle he
rose to the surface, puffing and blowing, and scrambled out.

“Well, here’s a fix,” thought Ding-dong, “just like my luck. I’m always
getting in bad.”

All this time he had quite forgotten about the two dark, moving
objects, to whom he owed his present predicament. But their existence
was rudely recalled to him as, out of the darkness, something rushed at
him, snorting loudly and angrily, and advancing like an express
locomotive.




                             CHAPTER XXIII.

                        OVERBOARD!—1950 FEET UP!


The adventure might have had a serious termination for the lad if Joe,
who had heard the collapse of the bank and the subsequent roar of the
avalanche, of which the luckless Ding-dong was the centre, had not
rushed to the river bank. Ding-dong, far too much astonished to raise
his rifle, was standing stupidly gazing at the animal that was rushing
toward him when Joe fired.

The creature gave a leap into the air, a queer kind of squeal, “like a
stuck pig,” Ding-dong said afterward, and fell dead.

The shot aroused every one on the _Discoverer_, and they came crowding
down to the river, to find Joe and Ding-dong examining, by their
electric pocket lights, the carcass of a large animal with a peculiarly
shaped snout. Explanations ensued, and the professor announced that it
was a tapir, a species of water animal common in South America.

Matco assured them that the meat of the creature was very good eating,
and much esteemed by his people, and he was permitted to cut some
steaks from Joe’s prize.

“If I hadn’t ter-ter-tumbled into that pool, though, he’d have been
mer-mer-mine,” declared Ding-dong positively.

“I guess you’d have been his,” laughed Joe, “that is, if you didn’t
move any quicker than you were when I saw you.”

“You watch me. I’ll do something great yet,” declared Ding-dong, with a
positiveness that deprived him of his stammer.

“It must have been great the way you went over that bank,” laughed Joe
unfeelingly.

The professor made Ding-Dong put on dry clothes, and then the
interrupted rest of the travelers was resumed. The remainder of the
night passed without incident, and a breakfast that took place soon
after dawn was eaten amidst much rallying of Ding-dong on his adventure
of the night before.

“I’d like to have seen any of the re-re-rest of you ber-ber-brave
enough to have gone near that snor-snor-snoring,” sputtered the lad,
valiantly helping himself to some more tapir steak, which was found to
be as good as the old Indian had declared was the case.

At eight o’clock the _Discoverer_ was ready to resume her flight. She
took the air without any accident, and under her replenished supply of
gas rose with tremendous buoyancy. In fact, the descending plane had to
be adjusted to keep her from shooting up too rapidly. No one on board
had any desire to repeat that flight to the chilly regions of the upper
air. As Ding-dong put it, “N-n-n-no more on my per-per-plate, thank
you.”

“Do you think we shall sight the city to-day?” inquired Nat, as he and
the professor stood on deck, just below, and in front of, the pilot
house.

“Impossible to say, my lad,” was the rejoinder. “As I told you, the
directions to reach it are vague in the extreme. We may have to cruise
about for several days before we satisfy ourselves of its existence or
non-existence.”

Nat looked disappointed. The boys, at a consultation among themselves,
had about decided that that day ought to find them at their long-sought
goal. Their expectation had been keyed up to such a height that delay
was exasperating.

At noon the professor took his observations, and declared that, if the
city existed in that part of the country, they ought to be within
striking distance of it.

Excitement ran at fever heat. The boys could hardly leave the deck to
eat a hasty meal. The field glasses were in constant demand. The
professor announced that he would donate a handsome rifle to the first
lad to spy a sign of the mystery of which they were in search.

If the boys had been eager before, this offer doubled their alertness.
Ding-dong even climbed into the rigging till he was sternly ordered
down by the professor.

“I thought if I got higher that I c-c-c-c-could see it s-s-s-sooner,”
he explained.

“As we are now at a height of two thousand feet,” observed the
professor, “I don’t think that a foot or two more of elevation would
give you a very much extended view.”

It was about one-thirty when Mr. Tubbs, who was at the wheel, called
the professor’s attention to something odd on the horizon. “It’s
glittering,” he said, “and may be a ledge of quartz or something.”

“Can you still see it?” asked the professor.

“No,” was the rejoinder. “It just flashed up for an instant,—like a
mirror in the sunlight,—and then vanished.”

“Keep a sharp lookout for its reappearance,” said the professor, with a
hint of suppressed excitement in his voice.

“Shall I steer in the direction in which I last saw it?” asked the
navigator of the _Discoverer_.

“Yes. If the old documents are correct we are so near to the location
of the lost city now that any clue is worth following.”

“Then you think that the glitter may have come from the city?” asked
Nat.

“I cannot say,” rejoined the professor. “It may have been that, or it
may have been the sunlight flashing, for an instant, on a hidden lake.”

“But wouldn’t a lake up here come pretty near to proving the existence
of the city we are in search of?” asked Nat.

“How do you draw such a conclusion?” inquired the professor, with
scientific exactitude.

“I thought you said the old documents said that the lost city was on an
island in a lake.”

“Ah, yes; but there may be many lakes of the kind described in these
regions,” was the reply. “Any more unusual signs yet, Mr. Tubbs?” he
asked presently.

“No,” was the rejoinder; but the moving picture man’s keen eyes scanned
the distance like those of a hawk.

It was an hour later that Nat, who had the glasses, set them down with
an excited face.

“I can see a lake!” he cried. “At least, I’m almost certain it is one.”

“Where?”

The professor’s voice had caught the infection of the boy’s excitement.

“Off there—in the same direction that Mr. Tubbs saw a glitter. I only
caught a glimpse of it, but it looked as if there was the glint of
water in among those queer, sharp-pointed peaks off there.”

“Speed up the engine if you can, Master Bell,” said the professor, with
an expression in his voice that the boys had never heard there before.

“We must investigate this at once and lose no time,” he went on. “The
old documents say that the lost city is on an island in a lake set in
the midst of mountains, over which there is no way of climbing but by
the lost and secret roads of the Incas.”

“I guess you get the rifle, Nat,” said Joe, without a trace of envy in
his voice, though.

“I w-w-w-wish I’d s-s-seen it f-f-first,” sputtered Ding-dong, who was
leaning far out over the rail.

“You’d have shot a tapir with the rifle, I suppose,” scoffed Joe.

“No; I’d have shot a-a——”

“Good heavens!” cried the professor, as both Nat and Joe sprang forward.

The abrupt conclusion of the stuttering boy’s speech had been caused by
the fact that, as he made it, he half turned, and losing his balance
plunged over the rail.

The _Discoverer_ was then nineteen hundred and fifty feet above the
surface of the earth!




                             CHAPTER XXIV.

                      THE CITY OF A VANISHED RACE.


But even in that instant of deadly peril, Ding-dong did not lose his
presence of mind, or, perhaps, instinct of self-preservation would be a
better phrase.

As he felt himself lose his balance, he clung to the network of the
rail, and hung there head downward between the sky and the earth for
one instant. But that brief molecule of time was enough for Joe and Nat
to secure his feet, as they flashed over the rail, and drag him back on
board.

“Go to the cabin, sir,” ordered the professor, who was white and shaky,
as, indeed, were the others.

There was no gainsaying his words, but Ding-dong, as usual, had to say
something. He was the most unperturbed person on board, in fact.

“I d-d-d-d-didn’t do it on p-p-purpose, you know,” he remarked, as he
walked off.

“Good heavens!” exclaimed the professor, leaning against the rail,
“what trouble is that boy going to get into next?”

The stuttering lad’s narrow escape had so unnerved them all that there
was no answer.

“Well?” said the professor at length, as if seeking a reply to his
question.

“Don’t ask me, sir,” gasped out Nat. “I haven’t got my breath back yet.”

It was, perhaps, half an hour later when the entire craft was
electrified by a cry from Joe.

“Nat was right! It is a lake!”

No need to ask to what he referred. The professor ordered the
_Discoverer_ sent higher, so as to give them a larger horizon, or,
rather, a bird’s-eye view.

As the craft rose upward in obedience to her planes, they saw beneath
them, but still at some little distance, what Nat has since declared
was the most wonderful sight he has ever seen or hopes to see.

Rimmed by bare, gaunt mountains, inhospitable and bleak, lay a small
lake, set like a turquoise in dull gold. In the midst of this lake was
an island, and on this island, even at that height, they could
perceive, were buildings rising in terraced formation. At the extreme
summit of the island, which rose to a peak, was something that flashed
and glowed in the sunlight almost blindingly.

“It’s the golden dome of the lost city!” gasped Nat.

“Say, Nat,” said Joe in rather a shaky voice, laying one hand on Nat’s
arm.

“What is it, Joe?” asked Nat, without taking his eyes off the wonderful
sight before him.

“Nothing; only—only I feel a bit scared,” was Joe’s quavering
confession.

“You may well feel awe-stricken,” said the professor, whose eyes were
gleaming, “ours are the first eyes to behold that island since the
mysterious catastrophe that wiped out the race that inhabited it,
occurred.”

There came a sudden voice at their elbows.

“L-l-l-looks like C-C-C-C-Coney I-I-Island.”

It was the incorrigible Ding-dong, who had taken advantage of the
excitement to slip out of his place of involuntary confinement.

But, in the general interest in all that was occurring, no attention
was paid to him. In the midst of the eager talk, and still more eager
scrutiny of the island, old Matco, who had come out upon the deck and
had stood silently gazing at the lost city, uttered a sharp cry.

Then, raising his hands above his head and fixing his eyes upon the
sun, he began muttering what seemed to be a prayer.

This done, he turned to the professor and poured out a rapid flood of
eager, emphatic words in his corrupt Spanish. So fast did he speak that
the professor had difficulty in following him. But by paying close
attention he managed to make out the old man’s meaning.

“What does he say?” asked Mr. Tubbs, as the old Indian ceased his
torrent of words, and leaned back, looking quite exhausted.

“Why, it’s like fiction,” said the professor. “The old man says that we
are fulfilling a tradition of his race which says that one day winged
men from the sky would discover the city.”

“Well, that’s a good omen,” said Nat.

“W-w-w-whatever that may be,” sputtered Ding-dong. “Guess you mean
n-n-no men.”

But the professor paid no attention to the irrepressible youth.
Instead, he assumed rather a grave look.

“Why, I’m not quite so sure that it is a good augury,” he said slowly.
“The old man says that the prophecy or tradition goes on to say that
the wrath of the long-dead Incas shall be visited on the violators of
their hidden city, and that a terrible end will overtake the sky men
who invade it.”

As the professor talked the old Indian fixed his eyes on him as if he
realized what he was saying. As the man of science concluded, he nodded
solemnly, as if indorsing all that had been told.

“Oh, well,” said Nat, “we are not going to turn back for the sake of an
old Indian ghost story.”

“Of course not,” said the professor; “but I thought if any of you are
superstitiously inclined, I would warn you.”

“I guess it would take more than talk like that to turn us back now,”
said Joe. “I’d face a legion of spooks to investigate that place.”

The others agreed with him. Indeed, as the _Discoverer_ grew nearer,
the marvels of the lost city grew more and more awe-inspiring.

What had appeared in the distance to be a mere huddle of terraced
buildings, were now seen to be stately palaces, some of them with trees
still growing amidst them. The buildings rose in this form till they
reached their climax at the great gold-plated dome that capped the
summit of the wonderful isle.

The walls, so far as could be seen, were white, but profusely
ornamented with barbaric magnificence.

Not a little of the mystic effect of the island was gained from the
precipitous and rugged cliffs of the mountains that walled the lake.

“However do you suppose a lake came to be in such a situation?”
wondered Nat, addressing the professor.

“In my opinion,” said the scientist, “that lake is what was once the
crater of a volcano, more enormous than any yet known.”

“And what we thought were separate mountains were once only part of the
summit of that volcano?” asked Nat wonderingly.

“I think we would be correct in assuming so. In many parts of the world
the craters of extinct volcanoes are found to be filled with water,
just as this one is.”

“The water must be of immense depth,” said Joe.

“In some cases it has been impossible to touch bottom, even with the
longest lines and the most perfect sounding apparatus,” was the
astonishing reply.

“But how does an island come to be in the middle of such a deep lake?”
was what Mr. Tubbs wanted to know.

“What we call an island is probably the summit of another peak of the
crater,” said the professor, “or it may have been formed, like those
volcanic islands of which we have such a keen recollection, by the
action of earth’s internal fires.”

The dirigible dropped lower. It was now almost directly above the lost
city. It could be seen that surrounding the golden dome was a vast,
semi-circular platform or courtyard of stone, with other stones set up
perpendicularly around it.

“It is precisely like the arrangement of the Temple of the Sun in
Peru,” said the professor.

“It will make a good place to land,” spoke the practical Joe.

“Doesn’t it seem almost like a sacrilege to bring a modern dirigible to
earth in the very courtyard where the rites of ancient religion were
practiced?” spoke Nat, who was an imaginative lad.

“Not at all,” said the professor, “and as for that ancient religion, if
we had lived in the days when it flourished, I fancy we wouldn’t have
liked it much. Like most ancient religions, it was a creed of bloodshed
and violence. Human sacrifices may have been indulged in on those very
stones we see beneath us.”

The boys agreed that this put quite another light on the matter, and
the descent was made without further comment. The dirigible came to
rest in the lost city of the Bolivian Andes at three o’clock in the
afternoon. Mr. Tubbs was left to guard the _Discoverer_ with old Matco,
who refused to move one step through the silent, long-deserted streets.
But the boys and the professor set out on a tour of exploration.

The streets, they found, were like those of mountainous cities in
Europe, and consisted mostly of steps. It was one of the most uncanny
feelings that any of them had ever experienced, this walking through a
city of the dead. For, although the ancient places were mostly in
ruins, from earthquakes the professor judged, the city yet seemed
lifelike enough for some of the vanished race to turn a corner at any
instant.

For some reason, the boys kept very close to each other and to the
professor, showing no disposition to wander. They found that, as they
approached the lake, the buildings grew poorer in character and were
not carved or decorated like those closer to the temple. The remains of
a splendid wharf remained, however, which set the boys to wondering
what had become of the boats that must have once plied between the city
and the shore.

This, in turn, suggested ruminations upon the means employed by the
vanished race of reaching the lake, for to climb over the mountains was
obviously impossible. The professor opined that, at some time, a tunnel
must have existed. This set the boys crazy to try to find it, but the
man of science declared that, in all probability, the tunnel, if it had
ever existed, had been ruined by earthquakes long since.

They stood by the lake side for a time looking into its dark blue
depths, and then began a return up the street, climbing the steps cut
in the rock.

“Where’s all the treasure we were going to find?” asked Joe, as they
climbed the steep causeway worn by the feet of a race long since passed
out of existence.

“I don’t imagine we are likely to find much that is valuable,” said the
professor. “My belief now is, that when the Spaniards came the
inhabitants of this city concealed everything valuable in it in some
place known only to themselves.”

“Maybe the lake bottom,” suggested Joe.

“That is not improbable. At any rate, I think we shall have to content
ourselves with the glory of having discovered this wonderful place. It
is far more perfect than the ruins of Peru are described as being.”

“What about taking that gold plating off the sacred dome?” said the
practical-minded Joe.

“Not with my consent,” said the professor. “I would wish this city to
be the Mecca of antiquarians from all over the world.”

“I agree with you,” said Nat. “It would be vandalism of the worst sort
to strip that rock.”

“Oh, I was only joking,” said Joe, with a rather red face.

“Here’s a peculiar-looking building,” went on Joe, a few moments later,
as they passed a tower-like structure, higher than the other buildings,
and without windows.

“Let us survey it,” said the professor. “See, here is a door. It has
fallen in, it is true, but I imagine we can squeeze through.”

By dint of getting on their hands and knees they managed to crawl under
the richly carved and broken portal, Nat pausing to notice that the
carvings seemed to be of various astronomical bodies.

Within the tower they found themselves standing at the bottom of a
tall, narrow, perpendicular shaft. It was, in fact, like looking up a
circular chimney. At the top was something which at first sight seemed
to be a big glass lens; but the professor pronounced it to be pure
crystal.

“This is the most amazing find yet!” he exclaimed with enthusiasm. “I
believe that this tower formed a sort of rude telescope, through which
different observations were carried on.”

He clasped his hands in scientific fervor. Indeed, they had seen enough
that afternoon to turn the brain of the least imaginative man of
science!

Nat informed the professor of the carvings he had noticed.

“That settles the matter,” said the professor enthusiastically. “Good
heavens, what a find! It has long been a controversy between various
scientific men as to whether or no the ancient races understood
astronomy in the true sense. The finding of this rude telescope will go
far toward—— Gracious! what was that?”

“What?” cried Nat, considerably startled.

“Why, a hand reached out and grasped my hat and——”

Before the professor could conclude his sentence the boys saw a small
brown paw project from a ledge above him and whisk his unlucky hat from
his head.

“It’s a monkey!” cried Nat.

“A lot of them!” exclaimed Joe.

“T-t-t-there they go,” cried Ding-dong, as a dozen or more apes of the
prehensile tailed type rushed off amidst the ruins, chattering and
squealing and tearing and clawing at the professor’s unlucky headgear.

“Just to think,” sighed the man of science with resignation, “that I
came all this way, and we have made all these discoveries, and yet my
ill-fortune with hats pursues me still.”

“I’d give several dozen hats to have seen what we’ve seen,” Nat
reminded him.

“That is so! that is so!” Professor Grigg agreed; “but——”

“Look out!” cried Joe, behind him, suddenly.

The professor leaped back just as an ugly flat head, with a pair of
malicious leaden eyes, protruded itself at his elbow from between the
crevices. It was the head of an immense snake.

Without more ado the explorers made haste to get out of the
astronomical tower.

“Exploring is certainly strenuous work,” commented Joe as they gained
the open air.

“Yes; I don’t wish to do any more without a rifle,” agreed Nat.




                              CHAPTER XXV.

                          A STRANGE ADVENTURE.


Early the next day the explorers, boys and adults, resumed their
investigation of the Lost City. The professor estimated that it would
take some time before they had completed their work and collected
relics, records and films of the various features of absorbing
scientific interest to be found there.

Joe and Nat struck out in one direction, while the Professor, Ding-dong
and Mr. Tubbs assumed another line of investigation. The path taken by
the two boys led them down one of the crumbling streets to the lake
front of the Lost City. On the way they entered several of the houses
and collected some small relics and Joe, who had some talent that way,
busied himself in making rough sketches of the buildings they examined.

At last, thoroughly tired out, the two lads sat themselves down on a
raised pile of carefully fitted stones in the courtyard of a splendid
white building with a pyramid-like cupola. They had brought some
sandwiches and a flask of water with them and made a light meal while
they rested.

“Seems like a sort of sacrilege to be eating corned beef sandwiches in
what may have been a temple,” said Nat as he ate.

Joe laughed.

“From what we know of the folks that used to live here they used to
make corned beef out of anyone they didn’t like, so don’t worry about
that end of it, old fellow.”

“That’s so,” agreed Nat. “I wonder, for instance, if this business
we’re sitting on at this moment isn’t an old altar of some kind. Looks
as if it might have been.”

“It does that,” agreed Joe, “and see here, Nat, here’s a metal ring
right here in this slab of stone. I wonder if they used to tie their
poor victims to it?”

He indicated a big ring of dull, greenish metal which they had not
noticed before. It was countersunk in one of the slabs of stone that
formed the top of the altar.

Nat examined it.

“I guess more likely it was used to raise this stone,” he said. “Maybe
the altar is hollow inside and contains relics of some sort.”

“Cracky! I’d like to raise it,” declared Joe; but, although he tugged
and pulled till his ruddy face was redder than usual, Joe could make no
impression on the stone.

“Let me try,” suggested Nat.

With what idea, he could not exactly say, the boy gave the ring a
gentle twisting motion instead of tugging at it. Then an astonishing
thing happened. The entire top of the altar tipped downward and the
boys were shot, scrambling and struggling, into the interior of the
altar, if such it had been. Before they knew just what had occurred
they found themselves in total darkness, for, having tipped them off,
the stone had swung into place again.

A thrill of fear crept icily through Nat’s veins as he realized that
they were prisoners. But he put all the heart he could into his reply
when Joe in a frightened voice gasped out:

“What on earth happened, Nat?”

“Why, just this,” was the reply. “That altar top was counterbalanced.
Our weight was on one end of it. In some way, when I twisted that ring,
a spring or catch must have been loosened and—and—we’re in the interior
of the altar.”

“Can we get out again, do you think?”

“That’s just what we’ve got to find out, and quickly, too, Joe,” was
the response. “Got any matches?”

“Yes; luckily I brought some. I’ve got a pocket lantern here, too, with
a candle in it. Shall I light up?”

“Yes, do so as soon as you can,” rejoined Nat.

The next minute the interior of the altar was illumined by a yellow
light. But so perfectly had the swinging top of the altar been fitted
that not a crevice appeared and as for any lever or handle by which it
might have been opened, none was revealed by the light.

But it was some minutes before the boys found out this fact. When they
did, however, it came with a sense of stunning bitterness. If they
could not find a means of egress from the altar, they were, in all
human probability, doomed to die in that gloomy prison.

Although they both realized their situation, neither lad voiced his
fears. There still remained one end of the altar to be examined, and
Nat lost no time in proceeding to investigate the hitherto neglected
portion of their prison. But its masonry appeared to be as solidly
constructed as was the case in every other part of the altar. Nat,
almost in despair, was turning away when Joe, who had been at his side,
gave a sudden cry.

“Nat! Nat! There’s a stone loose here. I can move it with my foot. When
I press down on it—Great-jumping-horned-toads!”

Joe’s exclamation was caused by the fact that as he pressed down on the
loose stone a small door opened out before them in the end of the
altar. It was impossible to say, however, whither it led, as beyond lay
total darkness.

“What do you say, shall we try it?” asked Joe in a rather tremulous
voice, for the darkness looked singularly mysterious and forbidding.

“We’ve _got_ to try it,” said Nat gloomily. “It’s our only alternative,
unless we want to stay here and starve to death.”

Joe had to agree that this was a true statement of the facts of the
case, and not without quickened pulses the two lads made the plunge
into the darkness beyond the door. The portal was square and so low
that they had to bend to get through it. The rays of Joe’s
candle-lantern showed the two youths that they were in a low-roofed
passage, or tunnel, just wide enough for them to proceed in single file.

“You go first,” said Joe in a rather quivery tone, which showed better
than anything else that the adventure was having its effect upon him,
the usually unperturbed.

“All right, give me the lantern.”

“I wonder where this passage can lead to?”

“Haven’t the least idea. I think we are going south, but I’m not sure.”

“I’m all twisted up, too. I wish we’d left that old ring alone.”

“Maybe I don’t, too. If we ever get out of this place, I’ll leave all
such devices severely to themselves in future.”

“Have you any idea of the purpose of this passage?”

“Not I. Maybe it was used as a means of escape. In that case——”

“In that case we will get out to daylight again,” Joe concluded.

“On the other hand, it may have been designed as a means of executing
their criminals or enemies. I’ve heard of such things.”

Joe fairly shuddered.

“Oh, talk of something pleasant,” he said, with a groan.

No more was said for a time. The circumstances didn’t make the boys
feel much inclined for conversation.

All at once they emerged into a vaulted chamber, seemingly cut out of
the living rock. At the top of its arched roof was set a huge crystal,
very like the one they had seen in the “telescope tower,” only much
larger. Through this lens light was streaming into the place, the walls
of which were painted and carved with all manner of strange-looking
inscriptions and designs. Nat was so intent on gazing at these that he
did not look as carefully where he was going as he had in his progress
down the passage.

Suddenly his feet slipped from under him and he found himself falling
downward. Joe uttered a cry as he saw his comrade vanish. He leaped
forward, checking himself just in time to avoid sharing Nat’s plight.
He found himself on the brink of a sort of well about ten feet deep. At
the bottom of this was Nat. Joe uttered a cry of relief as Nat hailed
him and assured him that, by a miracle, he was not hurt.

“But how are you going to get out of there?” demanded Joe the next
instant.

How, indeed? The question certainly was a poser. The walls of the well
were as smooth as glass almost and Joe noticed a peculiar feature. From
its “curb” radiated long lines extending over the floor of the rocky
chamber. These lines were cut in the rock and reminded Joe of lines he
had seen cut on a sun dial.

But he gave little thought to this at the moment. His mind was centered
on finding a means to get Nat out of his predicament. But, though he
thought and thought, no solution of the problem occurred to him.

Joe was still wrapped in thought at the edge of the well when he felt a
sudden blast of fearful heat on his back. He looked hastily round. His
first thought was that some hidden fire must suddenly have burst into
life behind him.

But, no, what he had felt had been the rays of the sun pouring through
the crystal at the top of the cavern and striking down with
tremendously magnified force upon him.

“Phew! That felt like an oven!” exclaimed Joe, moving away.

It was a moment later that he observed something that filled him with a
vague sense of alarm, which swiftly crystallized into a sharp, livid
pang of fear.

The sun was now striking down into the well. Like a thunderbolt the
purpose of the pit and the reason of the crystal lens burst upon Joe.

The ancient dwellers of the Lost City had been Sun Worshippers. This
chamber was a sacrificial one and the priests of the vanished race had
offered up their victims’ lives by literally dedicating them to the Sun
gods. As this alarming truth broke upon Joe a faint cry came from Nat,
down in the pit.

“Joe, for gracious sake, do something to get me out of here! The sun is
striking down into the pit. It is fearfully hot. If you don’t get me
out soon I’ll be baked alive.”

Poor Joe cast his eyes about him despairingly. The sun was streaming
through the lens at an angle now. What would happen when its direct
rays poured down into the narrow well he could not bear to think.




                             CHAPTER XXVI.

                        SAVED FROM THE SUN GODS.


Suddenly a thought struck him. Perhaps by joining his belt and Nat’s
together and then leaning over the edge of the pit he could haul his
unfortunate chum up to safety. It was worth trying, anyway.

Going to the edge of the pit and leaning over, Joe communicated his
idea to Nat. By this time the sun was streaming dazzlingly into the pit
and only by crouching in one corner could Nat escape its ardent rays.
Acting on Joe’s instructions, Nat took off his belt and threw it
upward. After one or two trials Joe managed to catch it. Then, taking
off his own, he joined the two together. Then he extended himself at
the edge of the well, and, reaching out his arm to the utmost, lowered
the two joined belts down to Nat. They were about a foot too short for
Nat to reach them even with the utmost endeavor of which Joe was
capable!

Things began to look black, indeed. Momentarily the sun was nearing the
zenith, and the place into which Nat had fallen was so designed that
when the luminary reached its highest point in the skies the excavation
would be filled with its rays, magnified many times by the crystal
lens. The lens, in fact, was nothing more nor less than an immense
burning-glass designed to shrivel up the victims of the ancient
priesthood. How little those who invented such a cruelly ingenious
device could have imagined that a boy of the twentieth century would
ever be in danger of losing his life by it! Yet such was the case and
neither Nat nor Joe could conceal the fact from themselves an instant
longer.

“Can’t you think of anything? Don’t you think you could climb up just a
foot or two?” asked Joe, despairingly.

“The walls are smooth as glass. I don’t believe a fly could get a hold
on them,” was the rejoinder. “Joe, the heat is getting awful!” gasped
out poor Nat in conclusion.

“Gracious! What am I to do?” cried Joe to himself. He rose to his feet
and gazed about him. Suddenly a thought struck him. If the priests, as
seemed only too probable, really roasted people to death in that well,
they must have had some means of getting the bodies out. How did they
do it? It must have been by a chain or rope, or something of the sort,
was the thought that struck Joe after a minute’s reflection. In that
case the chain, or whatever they used for the purpose of extricating
their victims, must be somewhere in the chamber.

“I’ll find it, if it’s anywhere within reach,” determined Joe.

Then he hailed Nat in as cheerful a voice as he could muster. He told
him what he was going to do and begged him to keep up his courage. Nat
replied bravely that he could hold out a while longer; but the weakness
of his voice made it painfully evident that if help was to be furnished
him it would have to come quickly or be too late.

Joe noticed, now that his sight was quickened by the need of hasty
action, that off at one side of the chamber was a recess cut in the
rocks. He hastened over to it and found that within it was an ancient
chest of some sort of sweet-smelling wood. This was so dry-rotted with
the ages that a vigorous kick of the lad’s foot smashed the moldering
lock off and Joe hastily threw the lid open.

He could not refrain from uttering a cry of joy as his eyes noted its
contents, some spears, axes, of stone or flint—whose former purpose
seemed only too evident—and, best of all, a coil of chain, forged of
the same peculiar greenish metal as the ring had been.

“Hurray!” shouted Joe as he dragged out the chain, “this is what we
wanted. Now I’ll have Nat out in no time.”

Hastening back to the lip of the well with the chain, he dangled its
end, which terminated in a hook, over the edge. As he did so he gasped
at the hot fumes which arose from the cylindrical pit. Joe was only
just in time. Nat had barely strength enough to fasten the chain under
his armpits and begin scrambling up as Joe hauled with all his might.

But if the hole had not been small enough in circumference for Nat to
brace his legs against one side of it and help work himself up in this
way, Joe would never have got him out. As it was, the task almost
exhausted the strength of both boys, and when it was completed they lay
gasping at the edge of the well for some moments, utterly unable to
command their limbs.

Joe was the first to recover. The sun had now reached the zenith, and
through the mammoth burning-glass was pouring hotly into the well. A
sudden idea struck Joe. He tore a bit of paper off an old envelope he
happened to have in his pocket and let it flutter into the pit.

As it dropped waveringly the paper turned brown, then black, and as it
struck the bottom of the sun-heated pit it dissolved altogether into
shrivelled cinder.

Joe turned away from the pit with a shudder. The thought of the
fearfully narrow escape Nat had had almost unnerved him. But for Nat’s
sake he did not let the other lad see how shaken he was. Shortly after
Nat, though still weak, was sufficiently recovered to get shakily to
his feet. Then the two lads set about to find a way out of the
sacrificial cave. First, however, they armed themselves with a
stone-axe apiece.

The arched entrance of another passage than the one by which they came
opened off on one side of the cavern, and as they peered into it they
could feel a sharp puff of delightfully cool air. “That means that this
passage leads out into the open,” cried Nat gleefully. “Come on, Joe,
we’ll soon be out of this mess.”

Joe, rejoicing as much as Nat, followed the young leader of the Motor
Rangers. As they advanced the air blew upon them cleaner and sweeter
every instant. Both lads inhaled it in great lungfuls. It seemed as if
they could never get enough of it after that oven-like chamber of the
sun.

“I wonder what part of the city we’ll come out in,” said Nat presently.

“Near the camp, I hope. How astonished the others will be when we tell
them of what has happened to us! I’ll bet they’ve had a tame time
compared to ours.”

“I hope so for their sakes,” said Nat with a laugh, “but I guess we are
out of the woods now.”

But were they? It seemed to the two young Motor Rangers, a moment
later, that they were not by any means “out of the woods,” as Nat had
phrased it.

Instead, they soon found themselves at the mouth of the passage; but as
far from finding their friends as ever. For the tunnel emerged in the
face of a precipitous cliff, below which glittered the waters of the
lake. It was a cruel disappointment.

While they still stood there, almost crushed by the sense that after
all they were still prisoners—and apparently hopeless ones—a startling
thing happened.

In the passage behind them distant voices sounded!

Human voices they were beyond a doubt. They were borne to the ears of
our two young friends with the booming sound produced by the tunnel,
which formed, as it were, a giant speaking-tube.

The boys exchanged alarmed glances. Who could these denizens of the
subterranean world of the island be? Survivors of the cruel race of
whose practices they had just had a terrible revelation? Robbers, or
worse, who had made the Lost City their rendezvous? Or was it, after
all, a trick of the imagination?

Determined to test this last idea, Nat slipped a short distance into
the tunnel and listened intently.

A few seconds satisfied him that their imaginations had played them no
pranks. Voices, far off, but apparently coming nearer, could be
distinctly heard. Nat turned faint and sick for an instant, and a
glance at Joe’s face showed him that his companion, too, was badly
shaken. Nat did not blame him. The knowledge that mysterious beings of
some sort were within the tunnel and coming toward them—perhaps on
their track—gave him a most uncomfortable thrill.

He glanced down from the ledge on which they stood. The cliff face was
smooth, although some metal rings showed that a ladder must once have
existed by which the lake might be reached. Above the mouth of the
tunnel the precipice was sheer also.

They were fairly trapped. As they realized this each lad instinctively
grasped his stone-axe tighter. Nat crouched behind a boulder and Joe
squeezed in close beside him.

“Who do you think they are?” he quivered, “survivors of the Lost Race,
or—or——”

“I don’t know,” rejoined Nat, with what composure he could summon, “but
this I do know, that they are not likely to be friendly if they find
us.”

“Then there is a chance——”

“Yes, a chance that they may not come as far as this, or may not see
us. They may be crossing some intersecting passage from a higher level.”

But a few minutes later the voices grew louder. The perspiration broke
out on Joe’s forehead. He gripped his axe more tightly, but the sense
of the mystery surrounding the beings who were approaching made him
catch his breath in agitation. He felt as if he were in some nightmare.

“Mind! Don’t make a hostile move unless they attack us first,” warned
Nat in an impressive whisper.

The next instant a high-pitched voice came booming down the tunnel.

“S-s-s-s-say this bub-bub-beats the Sub-ub-ub-ubway!”

“Jumping hop-toads! That’s Ding-dong Bell!” cried Joe, dashing down his
hammer.

“And the professor!” cried Nat as another familiar voice came toward
them.

“And Mr. Tubbs! What on earth!”

With wild whoops of joy the two boys who an instant before had been
expecting to face, they knew not what, peril, rushed to meet their
friends. They were in such a hurry that they narrowly escaped being
shot, the other party being as much alarmed at their approach as they
had been at the advance of the professor and his companions.

Matters were soon explained. The professor and his comrades had found
the mouth of a tunnel in an old temple. Entering this, it had brought
them underground. Some distance above the lake end of the tunnel which
the boys had traversed, the passage by which the professor had
travelled joined it. The hurry of Nat and Joe to reach the fresh air
explained why they had not noticed the branch passage. Had they done so
and followed it they would have come out not far from camp.




                             CHAPTER XVII.

                         “DID WE DREAM IT ALL?”


The search of the ruins was prosecuted with vigor for several days more
before they stumbled upon anything in the way of “te-ter-treasure,” as
Ding-dong Bell called it. But during that time the boys’ eyes had been
so satiated with wonders of ancient architecture and carvings, that
they had almost forgotten about the more material part of their quest.

One afternoon Nat and Joe had set forth to explore a temple which,
hitherto, had not been entered. The professor would have accompanied
them, but he was busy working up his field notes into his journal, and
compiling in systematic form descriptions of the wonders of the island.
Mr. Tubbs and Ding-dong had gone off making photographs, of which a
goodly number had been taken, not forgetting several motion pictures,
showing the explorers at work.

“Suppose we take a look over that queer, oblong building,” said Joe, as
they set out, indicating a smaller building than the others, not so
very far removed from the grand circle of structures fronting on the
circular Sun Temple, which formed the “hub” of the island.

“Very well,” said Nat; “but I don’t suppose it contains anything but a
replica of what we’ve seen already.”

“Well, inasmuch as the professor has made up his mind not to leave the
island till everything has been explored and recorded, we might as well
see what we can see in there,” went on Joe.

So the two lads set forth on their tour of exploration. The door of the
temple they had elected to investigate was in fairly good preservation,
the lintel post not having cracked, as was the case with most of the
other buildings. The usual condition was an evidence of the severity of
the earthquakes that must, from time to time, have shaken the island.

Passing through the entrance they found themselves in pitchy darkness.
But, as they had long since found electric flashlights needful articles
in searching the ruins, they soon had drawn out a couple of these and
illuminated the gloom.

“This is a queer sort of place,” remarked Nat, looking about him as
they flashed the lights hither and thither, “I wonder if the same
peculiar feature about it has struck you as it has me.”

“What is that?” asked Joe.

“Why, in every other one of these old temples and ruins we have seen,
there was every provision for the admittance of light; in fact, the old
Incas were sun worshippers.”

“I see what you mean now,” cried Joe eagerly. “This place hasn’t a
window in it.”

“No; that’s odd, isn’t it? I wonder if, by any chance, this can be the
Temple of the Moon that the professor was anxious to discover.”

“By George! I shouldn’t wonder if you’ve hit on the explanation, Nat.”

“Do you think so?”

“I do.”

“Well, let’s carry on our investigations.”

“By all means. We may be on the verge of a great discovery of some
sort.”

“I hope we don’t discover any more snakes.”

“Same here. Those beasts get on my nerves.”

“We’ve seen enough of them in the last few days to make you get
accustomed to them.”

“That is true; but just the same, the more I see of them the less I
like them. These ruins all seem to be alive with them.”

“I guess they are common in every part of this country.”

“Ugh! I can never think of that one that almost got poor Ding-dong
without a shudder.”

“Well, let’s push on. This place seems to have a sort of dome for a
roof.”

As he spoke, Nat flashed his light up till its beam of radiance showed
a finely modeled but low dome above them. As the light fell on the
concave structure, the lad gave a cry.

“Look, Joe! Look!”

“What? Where?”

“Up there, right above us!”

“Why, it’s a huge silver moon embossed on the dome!”

“That’s what it is. There is almost as much silver there as there is
gold on the sacred dome. Those old fellows were not sparing with
precious metals.”

“I should say not. But what’s that over there, Nat? Surely it’s a door.”

“Looks like one, anyhow. Let’s try it and see.”

The two lads crossed the stone floor, upon which the dust of the ages
lay thick and rose in choking clouds, and reached the portal which Joe
had pointed out. The great ring affixed to one side of it was of some
peculiar sort of metal, not unlike bronze, and was untarnished.

Not without a faster beating of his heart, Nat turned the ring. It
moved easily, and as it did so the door swung outward. It was of stone,
and massive as the living rock itself.

Within they made out a flight of stairs that led steeply upward into
the darkness.

“Are you game to try them?” asked Nat.

“Am I? I wouldn’t go out of here without seeing where they lead.”

“Well, go easy. They might give way. Heaven only knows how old they
are.”

But the stairs proved solid. They wound upward steeply, worming their
way around a central pillar covered with carvings. At last the boys
emerged on a kind of platform at the top, which was roofed in by an
irregularly shaped covering. Right in front of them were two round
holes placed at some distance apart, and at their elbows were some
curious-looking bits of apparatus. One of these looked like a gigantic
bellows, and another was not unlike a megaphone in form.

“Well, where on earth are we now?” gasped Joe.

“I don’t know, but light is coming in through these holes. Let’s look
out and see.”

The boys each took one of the circular windows and peered out. To their
astonishment they looked into a vast cavernous chamber, lighted from
the summit which admitted sunshine, the roof of which was supported by
pillars. It was so vast that it took the breath away almost, to gaze
into its great distances and heights.

The floor of this place was marked with a circle, about which were
inscribed signs at regular intervals.

“Must have been their equivalent for the signs of the zodiac,” breathed
Nat, awestruck at the enormous spaces before him.

“Then this was a temple,” said Joe looking down from his window at the
great floor, which was fully twenty feet below where the boys stood
peering.

“It must have been,” gasped out Nat, “and—and—Joe, we are in the very
holy of holies of this island.”

“What do you mean?”

“Can’t you see? Look below you. We are peering out of the eyes of a
huge idol made out of the rock. That stuff at the head of the stairs
must have been the apparatus the priests used to make the idol speak
and utter terrifying noises.”

There was no question but that Nat was right. Both boys could now make
out beneath them, the rounded outlines of a huge squatting figure. In
the head of this monstrous figure—its eyes, in fact—were the two
circular holes through which they were looking.

“Gracious, what a sight it must have been when that temple was full of
people of the vanished race, adoring this great idol,” murmured Nat, in
awestruck tones.

“And what a job the priests must have had fooling them through that
megaphone and that big bellows,” said Joe, the practical.

“That wouldn’t have detracted from the grandeur of the scene. It must
have all been very real to them. Why, this place must be as vast as the
hugest cathedral.”

“It gives me the shivers,” said Joe. “Hark, how your voice goes echoing
off there among the pillars.”

“I wish there was some way of climbing down through these eyes. I’d
like to explore that temple. I wonder where the entrance is.”

“Must be on the other side of the island. In the meantime, let’s look
at the head of the stairs there, and see if we can discover anything
else.”

The boys flashed their lights about among the pile of mouldering relics
and machinery of the ancient priests. Suddenly Nat gave a shout of
triumph.

“What do you make of this?”

“This” was a huge chest, the lid of which, bound and embossed with
dully glittering metal, was open. It was full of various articles, some
of which gleamed and flashed with gems. Nat plunged in his hand and
drew out a golden breastplate. Joe followed this discovery by drawing
forth a cup of what seemed to be pure turquoise. Various head-dresses
of precious metal, more cups and vessels of gold, all jewel studded,
followed.

“Well, we’ve found it,” breathed Nat; “we’ve found it, Joe, old boy.”

“Yes, and now we have, let’s take what we can of this stuff and get out
of here,” said Joe. “We’ll come back with more lights and company. It’s
getting kind of creepy and lonesome in the dark here.”

The boys loaded themselves with all they could carry, including the
turquoise cup, and stumbled down the stairway. It did not take them
long to retrace their steps and dump down their prizes in front of the
astonished professor. He declared that the value of the turquoise cup
alone was inestimable, while the jewels in some of the breastplates and
vessels were worth more than he dared to name.

“I should say that what you have here would fetch two hundred and fifty
thousand dollars in the value of the jewels alone,” he said. “As to
what they are worth as relics of a vanished race, I am not prepared to
say.”

Half an hour later, while they still sat awed and silent about the pile
of wonderful relics, Ding-dong Bell appeared lugging an armful of
photographic plates.

“We got some dandy pictures,” he began, “we—— Wer-wer-well, I’ll be
jer-jer-jer-jig-gered!”

For the first time in his life Ding-dong Bell was fairly taken aback
and bereft of all speech. He could only stand and blink in owl-like
fashion at the marvelous display laid out before him.

                  *       *       *       *       *

“Nat! Nat! wake up!”

The voice sounded in the ear of the leader of the Motor Rangers, and
was accompanied by a violent shaking of his shoulder.

“What is it, Joe? Here, quit shaking my bed, I——”

“I’m not shaking your bed, Nat. It’s the whole island that’s shaking!
Quick, help me arouse the others!”

Nat was awake in a flash. As he hastily drew on some clothes a strange
moaning noise filled the air. It was followed by a rushing sound
overhead.

“It’s an earthquake!” exclaimed the professor, as soon as he was
awakened.

As he spoke the whole structure of the _Discoverer_ was shaken as if by
a giant hand beneath her.

At the same instant the voice of old Matco was heard calling out as if
in prayer.

“Get her loose, for heaven’s sake!” cried Mr. Tubbs, “or we’ll be
destroyed!”

“It is the vengeance! The vengeance!” cried old Matco in Spanish,
bursting into the cabin.

“Switch on the lights,” ordered the professor.

Joe sprang into the pilot house and threw the switch. A blaze of light
illumined the aircraft. It showed a strange scene in her cabin.
Half-dressed, and wholly bewildered, the adventurers were being thrown
about like so many ninepins. The substructure of the _Discoverer_ shook
like an ague-stricken human being, as the earth beneath her rocked and
rumbled.

Nat and Joe, the most self-possessed of any on board, sprang out upon
the decks. The ropes had been tied, it not having been anticipated that
they would want to leave in a hurry.

“Cut them!” shouted Nat above the hubbub about them.

The sky was being ripped and seared by livid lightning, while the
flashes of light showed the lake to be a mass of white foam. The air
was filled with a strange, roaring sound.

It was the voice of the earthquake. Nat had heard it once before in
California.

As the boys’ knives fell on the ropes, the _Discoverer_ shot upward. Up
and up into the lightning-riven sky she arose, while beneath them the
earth shook and rocked and rumbled.

“Great Scott!” cried a voice,—it was Nat’s,—“if ever we get struck by a
flash of that lightning,—good-bye!”

The words sounded flippant, but the danger was real. The boy recalled
reading of the fatal disaster to the great Zeppelin dirigible in a
thunder-storm. But still they could not seek a refuge on the earth, at
any rate not on the island. The air was the only place for them to seek
safety.

The noise all about was nothing less than terrific. Voices could not be
heard unless raised to a shout. The rigging of the dirigible creaked
and groaned as the great bag swayed, and added to the distracting
turmoil.

Paralyzed by the very suddenness and utter unexpectedness of it all,
the adventurers for a time merely clung to the rails of their swaying,
madly careening craft. How that night passed, none on board was exactly
able to tell in after days.

They got the engine going, and held the big cloud cruiser as close to
the earth as they dared, using the descending planes to steady her
under the wild swaying of the great gas bag. A furious wind accompanied
the earthquake, and when the lightning died away it seemed as if there
was to be fresh and even more deadly peril, from the possibility of the
great gas container being ripped bodily from the substructure.

But the rigging held tightly, and dawn found the disturbance almost at
an end. It was a shaken, white-faced crew that regarded one another in
the gray light. The night had been one to try the nerves of a man of
iron, and the Motor Rangers were only youths.

However, the storm died out almost as swiftly as it had come, and
breakfast and hot coffee heartened them wonderfully. Even old Matco
plucked up his spirits, although, during the night, he was certain that
they were bound to perish in the anger of the old gods of his country.

After the morning meal they began to look about them. They found that,
during the night, they had been blown far to the southward of the site
of the lost city, but they could still make out the ragged peaks that
marked its locality.

The professor called a meeting, and it was unanimously decided to wing
back and find out how the island of the dead had fared. They reached
the spot by noon, and sailed over the peaks and gazed down into the
place where the island should have been.

But no island was there!

It had vanished as completely as if it had been a dream. Only the
waters of the lake rippled as placidly as of yore, hiding forever under
their azure surface the city that had been and now was not.

Silent and stunned the adventurers turned the _Discoverer’s_ prow
toward the westward once more.

“If it wasn’t for those relics in the cabin,” said Nat pensively, “I
should think that we’d dreamed it all.”

As he spoke he looked back toward the far horizon. Already the ragged
peaks were fading on the sky and soon would be out of sight.

“After all,” said the professor at length, “perhaps it is better so
than if that noble city of a vanished race had become the resort of
gossiping tourists.”

And in after days they agreed with him; but with Nat and Joe it was
long a bitter thought that they had left in the Temple of the Moon some
of the most marvelous remains of an ancient civilization ever
discovered.

                  *       *       *       *       *

The untimely ending of the existence of the wonderful island put an end
also to the Motor Rangers’ aerial adventures, for the professor decided
to abandon all attempts at relocating it and employing divers, as had
been his first intention.

The voyage north was made on the staunch old _Nomad_, and Mr. Tubbs and
the professor accompanied the boys. Old Matco received a substantial
reward, and decided to spend his last days in the shelter of Bolivian
cities rather than to take once more to the life of the forest.

As for Captain Lawless and his rascally mate, they were last heard of
roaming about Bolivia, still seeking for the lost city, of whose
destruction they were not aware. They had engineered an expedition with
their remaining money for this purpose, but not, of course, till after
their release from prison for firing at the airship. But as this was
only a brief incarceration, it did not delay their plans much. The
present chronicler is not in a position to state their ultimate fate.

It may be of interest to state here, that the crew they had so basely
deserted, managed to regain their schooner from the rascally old island
chief and sail her home, where they collected salvage from the owners.

The Motor Rangers enjoyed a long rest at home and then visited New York
to aid in classifying and arranging the pictures and relics of the lost
city. The cloud cruiser was sold to a syndicate, which long used her as
a passenger craft at fairs and exhibitions, and it is safe to say that
not one of her passengers ever dreamed of what the airship that carried
him had passed through.

Their exciting adventures above the earth will ever remain to the trio
of boys among their most thrilling recollections, says Nat; but in a
recent letter to a friend he hints that tiring of inactivity he and his
two chums have already started out in search of fresh incident and
adventure.

From what Nat says the tale of their experiences should form a suitable
sequel to the other volumes of this series, and it will be called: THE
MOTOR RANGERS’ WIRELESS STATION.


                                THE END.

------------------------------------------------------------------------

[Illustration]

Reasons why you should obtain a Catalogue of our Publications


_A postal to us will place it in your hands_


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standard books published, at prices less than offered by others.

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3. You will be able to purchase books at prices within your reach; as
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warrant us in making a reduction.

                       HURST & CO., _Publishers_,
                   395, 397, 399 Broadway, New York.

------------------------------------------------------------------------

                         =MOTOR RANGERS SERIES=

                       =HIGH SPEED MOTOR STORIES=

                            By MARVIN WEST.

        Cloth Bound. Illustrated. Price, 50c. per vol., postpaid


=THE MOTOR RANGERS’ LOST MINE.=

[Illustration]

This is an absorbing story of the continuous adventures of a motor car
in the hands of Nat Trevor and his friends. It does seemingly
impossible “stunts,” and yet everything happens “in the nick of time.”

=THE MOTOR RANGERS THROUGH THE SIERRAS.=

Enemies in ambush, the peril of fire, and the guarding of treasure make
exciting times for the Motor Rangers—yet there is a strong flavor of
fun and freedom, with a typical Western mountaineer for spice.

=THE MOTOR RANGERS ON BLUE WATER; or, The Secret of the Derelict.=

The strange adventures of the sturdy craft “Nomad” and the stranger
experiences of the Rangers themselves with Morello’s schooner and a
mysterious derelict form the basis of this well-spun yarn of the sea.

=THE MOTOR RANGERS’ CLOUD CRUISER.=

From the “Nomad” to the “Discoverer,” from the sea to the sky, the
scene changes in which the Motor Rangers figure. They have experiences
“that never were on land or sea,” in heat and cold and storm, over
mountain peak and lost city, with savages and reptiles; their ship of
the air is attacked by huge birds of the air; they survive explosion
and earthquake; they even live to tell the tale!

            Any volume sent postpaid upon receipt of price.

                  HURST & COMPANY—Publishers—NEW YORK

------------------------------------------------------------------------

                         =BOY INVENTORS SERIES=

                    =Stories of Skill and Ingenuity=
                           By RICHARD BONNER

        Cloth Bound. Illustrated. Price, 50c. per vol., postpaid


=THE BOY INVENTORS’ WIRELESS TELEGRAPH.=

[Illustration]

Blest with natural curiosity,—sometimes called the instinct of
investigation,—favored with golden opportunity, and gifted with
creative ability, the Boy Inventors meet emergencies and contrive
mechanical wonders that interest and convince the reader because they
always “work” when put to the test.

=THE BOY INVENTORS’ VANISHING GUN.=

A thought, a belief, an experiment; discouragement, hope, effort and
final success—this is the history of many an invention; a history in
which excitement, competition, danger, despair and persistence figure.
This merely suggests the circumstances which draw the daring Boy
Inventors into strange experiences and startling adventures, and which
demonstrate the practical use of their vanishing gun.

=THE BOY INVENTORS’ DIVING TORPEDO BOAT.=

As in the previous stories of the Boy Inventors, new and interesting
triumphs of mechanism are produced which become immediately valuable,
and the stage for their proving and testing is again the water. On the
surface and below it, the boys have jolly, contagious fun, and the
story of their serious, purposeful inventions challenge the reader’s
deepest attention.

            Any volume sent postpaid upon receipt of price.

                  HURST & COMPANY—Publishers—NEW YORK

------------------------------------------------------------------------

                          =BORDER BOYS SERIES=

                  Mexican and Canadian Frontier Series

                         By FREMONT B. DEERING.

        Cloth Bound. Illustrated. Price, 50c. per vol., postpaid


=THE BORDER BOYS ON THE TRAIL.=

[Illustration]

What it meant to make an enemy of Black Ramon De Barios—that is the
problem that Jack Merrill and his friends, including Coyote Pete, face
in this exciting tale.

=THE BORDER BOYS ACROSS THE FRONTIER.=

Read of the Haunted Mesa and its mysteries, of the Subterranean River
and its strange uses, of the value of gasolene and steam “in running
the gauntlet,” and you will feel that not even the ancient splendors of
the Old World can furnish a better setting for romantic action than the
Border of the New.

=THE BORDER BOYS WITH THE MEXICAN RANGERS.=

As every day is making history—faster, it is said, than ever before—so
books that keep pace with the changes are full of rapid action and
accurate facts. This book deals with lively times on the Mexican border.

=THE BORDER BOYS WITH THE TEXAS RANGERS.=

The Border Boys have already had much excitement and adventure in their
lives, but all this has served to prepare them for the experiences
related in this volume. They are stronger, braver and more resourceful
than ever, and the exigencies of their life in connection with the
Texas Rangers demand all their trained ability.

            Any volume sent postpaid upon receipt of price.

                  HURST & COMPANY—Publishers—NEW YORK

------------------------------------------------------------------------

                        =FRANK ARMSTRONG SERIES=

                  =Twentieth Century Athletic Stories=

                          By MATHEW M. COLTON.

        Cloth Bound. Illustrated. Price, 60c. per vol., postpaid


=FRANK ARMSTRONG’S VACATION.=

[Illustration]

How Frank’s summer experience with his boy friends make him into a
sturdy young athlete through swimming, boating, and baseball contests,
and a tramp through the Everglades, is the subject of this splendid
story.

=FRANK ARMSTRONG AT QUEENS.=

We find among the jolly boys at Queen’s School, Frank, the
student-athlete, Jimmy, the baseball enthusiast, and Lewis, the
unconsciously-funny youth who furnishes comedy for every page that
bears his name. Fall and winter sports between intensely rival school
teams are expertly described.

=FRANK ARMSTRONG’S SECOND TERM.=

The gymnasium, the track and the field make the background for the
stirring events of this volume, in which David, Jimmy, Lewis, the “Wee
One” and the “Codfish” figure, while Frank “saves the day.”

=FRANK ARMSTRONG, DROP KICKER.=

With the same persistent determination that won him success in
swimming, running and baseball playing, Frank Armstrong acquired the
art of “drop kicking,” and the Queen’s football team profits thereby.


            Any volume sent postpaid upon receipt of price.

                  HURST & COMPANY—Publishers—NEW YORK

------------------------------------------------------------------------

                        =OAKDALE ACADEMY SERIES=

                   =Stories of Modern School Sports=

                            By MORGAN SCOTT.

        Cloth Bound. Illustrated. Price, 60c. per vol., postpaid

=BEN STONE AT OAKDALE.=

[Illustration]

Under peculiarly trying circumstances Ben Stone wins his way at Oakdale
Academy, and at the same time enlists our sympathy, interest and
respect. Through the enmity of Bern Hayden, the loyalty of Roger Eliot
and the clever work of the “Sleuth,” Ben is falsely accused, championed
and vindicated.

=BOYS OF OAKDALE ACADEMY.=

“One thing I will claim, and that is that all Grants fight open and
square and there never was a sneak among them.” It was Rodney Grant, of
Texas, who made the claim to his friend, Ben Stone, and this story
shows how he proved the truth of this statement in the face of apparent
evidence to the contrary.

=RIVAL PITCHERS OF OAKDALE.=

Baseball is the main theme of this interesting narrative, and that
means not only clear and clever descriptions of thrilling games, but an
intimate acquaintance with the members of the teams who played them.
The Oakdale Boys were ambitious and loyal, and some were even
disgruntled and jealous, but earnest, persistent work won out.

=OAKDALE BOYS IN CAMP.=

The typical vacation is the one that means much freedom, little
restriction, and immediate contact with “all outdoors.” These
conditions prevailed in the summer camp of the Oakdale Boys and made it
a scene of lively interest.

=THE GREAT OAKDALE MYSTERY.=

The “Sleuth” scents a mystery! He “follows his nose.” The plot
thickens! He makes deductions. There are surprises for the reader—and
for the “Sleuth,” as well.

=NEW BOYS AT OAKDALE.=

A new element creeps into Oakdale with another year’s registration of
students. The old and the new standards of conduct in and out of school
meet, battle, and cause sweeping changes in the lives of several of the
boys.


            Any volume sent postpaid upon receipt of price.

                  HURST & COMPANY—Publishers—NEW YORK

------------------------------------------------------------------------

                       =DREADNOUGHT BOYS SERIES=

                        =Tales of the New Navy=

                         By CAPT. WILBUR LAWTON

                    Author of “BOY AVIATORS SERIES.”

        Cloth Bound. Illustrated. Price, 50c. per vol., postpaid

=THE DREADNOUGHT BOYS ON BATTLE PRACTICE.=

[Illustration]

Especially interesting and timely is this book which introduces the
reader with its heroes, Ned and Herc, to the great ships of modern
warfare and to the intimate life and surprising adventures of Uncle
Sam’s sailors.

=THE DREADNOUGHT BOYS ABOARD A DESTROYER.=

In this story real dangers threaten and the boys’ patriotism is tested
in a peculiar international tangle. The scene is laid on the South
American coast.

=THE DREADNOUGHT BOYS ON A SUBMARINE.=

To the inventive genius—trade-school boy or mechanic—this story has
special charm, perhaps, but to every reader its mystery and clever
action are fascinating.

=THE DREADNOUGHT BOYS ON AERO SERVICE.=

Among the volunteers accepted for Aero Service are Ned and Herc. Their
perilous adventures are not confined to the air, however, although they
make daring and notable flights in the name of the Government; nor are
they always able to fly beyond the reach of their old “enemies,” who
are also airmen.


            Any volume sent postpaid upon receipt of price.

                  HURST & COMPANY—Publishers—NEW YORK

------------------------------------------------------------------------

                         =BUNGALOW BOYS SERIES=

                     =LIVE STORIES OF OUTDOOR LIFE=

                        By DEXTER J. FORRESTER.

        Cloth Bound. Illustrated. Price, 50c. per vol., postpaid


=THE BUNGALOW BOYS.=

[Illustration]

How the Bungalow Boys received their title and how they retained the
right to it in spite of much opposition makes a lively narrative for
lively boys.

=THE BUNGALOW BOYS MAROONED IN THE TROPICS.=

A real treasure hunt of the most thrilling kind, with a sunken Spanish
galleon as its object, makes a subject of intense interest at any time,
but add to that a band of desperate men, a dark plot and a devil fish,
and you have the combination that brings strange adventures into the
lives of the Bungalow Boys.

=THE BUNGALOW BOYS IN THE GREAT NORTH WEST.=

The clever assistance of a young detective saves the boys from the
clutches of Chinese smugglers, of whose nefarious trade they know too
much. How the Professor’s invention relieves a critical situation is
also an exciting incident of this book.

=THE BUNGALOW BOYS ON THE GREAT LAKES.=

The Bungalow Boys start out for a quiet cruise on the Great Lakes and a
visit to an island. A storm and a band of wreckers interfere with the
serenity of their trip, and a submarine adds zest and adventure to it.


            Any volume sent postpaid upon receipt of price.

                  HURST & COMPANY—Publishers—NEW YORK

------------------------------------------------------------------------

                          =MOTOR MAIDS SERIES=

                    =Wholesome Stories of Adventure=

                          By KATHERINE STOKES.

        Cloth Bound. Illustrated. Price, 50c. per vol., postpaid


=THE MOTOR MAIDS’ SCHOOL DAYS.=

[Illustration]

Billie Campbell was just the type of a straightforward, athletic girl
to be successful as a practical Motor Maid. She took her car, as she
did her class-mates, to her heart, and many a grand good time did they
have all together. The road over which she ran her red machine had many
an unexpected turning,—now it led her into peculiar danger; now into
contact with strange travelers; and again into experiences by fire and
water. But, best of all, “The Comet” never failed its brave girl owner.


=THE MOTOR MAIDS BY PALM AND PINE.=

Wherever the Motor Maids went there were lively times, for these were
companionable girls who looked upon the world as a vastly interesting
place full of unique adventures—and so, of course, they found them.

=THE MOTOR MAIDS ACROSS THE CONTINENT.=

It is always interesting to travel, and it is wonderfully entertaining
to see old scenes through fresh eyes. It is that privilege, therefore,
that makes it worth while to join the Motor Maids in their first
’cross-country run.

=THE MOTOR MAIDS BY ROSE, SHAMROCK AND HEATHER.=

South and West had the Motor Maids motored, nor could their education
by travel have been more wisely begun. But now a speaking acquaintance
with their own country enriched their anticipation of an introduction
to the British Isles. How they made their polite American bow and how
they were received on the other side is a tale of interest and
inspiration.


            Any volume sent postpaid upon receipt of price.

                  HURST & COMPANY—Publishers—NEW YORK

------------------------------------------------------------------------

                          =MOLLY BROWN SERIES=

                    =College Life Stories for Girls=

                             By NELL SPEED.

        Cloth Bound. Illustrated. Price, 60c. per vol., postpaid


=MOLLY BROWN’S FRESHMAN DAYS.=

[Illustration]

Would you like to admit to your circle of friends the most charming of
college girls—the typical college girl for whom we are always looking
but not always finding; the type that contains so many delightful
characteristics, yet without unpleasant perfection in any; the natural,
unaffected, sweet-tempered girl, loved because she is lovable? Then
seek an introduction to Molly Brown. You will find the baggage-master,
the cook, the Professor of English Literature, and the College
President in the same company.

=MOLLY BROWN’S SOPHOMORE DAYS.=

What is more delightful than a re-union of college girls after the
summer vacation? Certainly nothing that precedes it in their
experience—at least, if all class-mates are as happy together as the
Wellington girls of this story. Among Molly’s interesting friends of
the second year is a young Japanese girl, who ingratiates her “humbly”
self into everybody’s affections speedily and permanently.

=MOLLY BROWN’S JUNIOR DAYS.=

Financial stumbling blocks are not the only things that hinder the ease
and increase the strength of college girls. Their troubles and their
triumphs are their own, often peculiar to their environment. How
Wellington students meet the experiences outside the class-rooms is
worth the doing, the telling and the reading.

            Any volume sent postpaid upon receipt of price.

                HURST & COMPANY - Publishers - NEW YORK

------------------------------------------------------------------------

                         =GIRL AVIATORS SERIES=

                        =Clean Aviation Stories=

                          By MARGARET BURNHAM.

        Cloth Bound. Illustrated. Price, 50c. per vol., postpaid


=THE GIRL AVIATORS AND THE PHANTOM AIRSHIP.=

[Illustration]

Roy Prescott was fortunate in having a sister so clever and devoted to
him and his interests that they could share work and play with mutual
pleasure and to mutual advantage. This proved especially true in
relation to the manufacture and manipulation of their aeroplane, and
Peggy won well deserved fame for her skill and good sense as an
aviator. There were many stumbling-blocks in their terrestrial path,
but they soared above them all to ultimate success.

=THE GIRL AVIATORS ON GOLDEN WINGS.=

That there is a peculiar fascination about aviation that wins and holds
girl enthusiasts as well as boys is proved by this tale. On golden
wings the girl aviators rose for many an exciting flight, and met
strange and unexpected experiences.

=THE GIRL AVIATORS’ SKY CRUISE.=

To most girls a coaching or yachting trip is an adventure. How much
more perilous an adventure a “sky cruise” might be is suggested by the
title and proved by the story itself.

=THE GIRL AVIATORS’ MOTOR BUTTERFLY.=

The delicacy of flight suggested by the word “butterfly,” the
mechanical power implied by “motor,” the ability to control assured in
the title “aviator,” all combined with the personality and enthusiasm
of girls themselves, make this story one for any girl or other reader
“to go crazy over.”


            Any volume sent postpaid upon receipt of price.

                  HURST & COMPANY—Publishers—NEW YORK

------------------------------------------------------------------------

                         =BUNGALOW BOYS SERIES=

                     =LIVE STORIES OF OUTDOOR LIFE=

                        By DEXTER J. FORRESTER.

        Cloth Bound. Illustrated. Price, 50c. per vol., postpaid


=THE BUNGALOW BOYS.=

[Illustration]

How the Bungalow Boys received their title and how they retained the
right to it in spite of much opposition makes a lively narrative for
lively boys.

=THE BUNGALOW BOYS MAROONED IN THE TROPICS.=

A real treasure hunt of the most thrilling kind, with a sunken Spanish
galleon as its object, makes a subject of intense interest at any time,
but add to that a band of desperate men, a dark plot and a devil fish,
and you have the combination that brings strange adventures into the
lives of the Bungalow Boys.

=THE BUNGALOW BOYS IN THE GREAT NORTH WEST.=

The clever assistance of a young detective saves the boys from the
clutches of Chinese smugglers, of whose nefarious trade they know too
much. How the Professor’s invention relieves a critical situation is
also an exciting incident of this book.

=THE BUNGALOW BOYS ON THE GREAT LAKES.=

The Bungalow Boys start out for a quiet cruise on the Great Lakes and a
visit to an island. A storm and a band of wreckers interfere, with the
serenity of their trip, and a submarine adds zest and adventure to it.

            Any volume sent postpaid upon receipt of price.

                HURST & COMPANY - Publishers - NEW YORK

------------------------------------------------------------------------

                          =BORDER BOYS SERIES=

                  Mexican and Canadian Frontier Series

                         By FREMONT B. DEERING.

        Cloth Bound. Illustrated. Price, 50c. per vol., postpaid


=THE BORDER BOYS ON THE TRAIL.=

[Illustration]

What it meant to make an enemy of Black Ramon De Barios—that is the
problem that Jack Merrill and his friends, including Coyote Pete, face
in this exciting tale.

=THE BORDER BOYS ACROSS THE FRONTIER.=

Read of the Haunted Mesa and its mysteries, of the Subterranean River
and its strange uses, of the value of gasolene and steam “in running
the gauntlet,” and you will feel that not even the ancient splendors of
the Old World can furnish a better setting for romantic action than the
Border of the New.

=THE BORDER BOYS WITH THE MEXICAN RANGERS.=

As every day is making history—faster, it is said, than ever before—so
books that keep pace with the changes are full of rapid action and
accurate facts. This book deals with lively times on the Mexican border.

=THE BORDER BOYS WITH THE TEXAS RANGERS.=

The Border Boys have already had much excitement and adventure in their
lives, but all this has served to prepare them for the experiences
related in this volume. They are stronger, braver and more resourceful
than ever, and the exigencies of their life in connection with the
Texas Rangers demand all their trained ability.

            Any volume sent postpaid upon receipt of price.

                  HURST & COMPANY—Publishers—NEW YORK

------------------------------------------------------------------------

                         =BOY INVENTORS SERIES=

                    =Stories of Skill and Ingenuity=

                           By RICHARD BONNER

        Cloth Bound. Illustrated. Price, 50c. per vol., postpaid


=THE BOY INVENTORS’ WIRELESS TELEGRAPH.=

[Illustration]

Blest with natural curiosity,—sometimes called the instinct of
investigation,—favored with golden opportunity, and gifted with
creative ability, the Boy Inventors meet emergencies and contrive
mechanical wonders that interest and convince the reader because they
always “work” when put to the test.

=THE BOY INVENTORS’ VANISHING GUN.=

A thought, a belief, an experiment; discouragement, hope, effort and
final success—this is the history of many an invention; a history in
which excitement, competition, danger, despair and persistence figure.
This merely suggests the circumstances which draw the daring Boy
Inventors into strange experiences and startling adventures, and which
demonstrate the practical use of their vanishing gun.

=THE BOY INVENTORS’ DIVING TORPEDO BOAT.=

As in the previous stories of the Boy Inventors, new and interesting
triumphs of mechanism are produced which become immediately valuable,
and the stage for their proving and testing is again the water. On the
surface and below it, the boys have jolly, contagious fun, and the
story of their serious, purposeful inventions challenge the reader’s
deepest attention.

            Any volume sent postpaid upon receipt of price.

                  HURST & COMPANY—Publishers—NEW YORK

------------------------------------------------------------------------

                        =The Famous Alger Books=

               By Horatio Alger, Jr.     The Boy’s Writer

                  ------------------------------------

A series of books known to all boys; books that are good and wholesome,
with enough “ginger” in them to suit the tastes of the younger
generation. The Alger books are not filled with “blood and thunder”
stories of a doubtful character, but are healthy and elevating, and
parents should see to it that their children become acquainted with the
writings of this celebrated writer of boys’ books. We publish the
titles named below:


                      Adrift in New York.
                      A Cousin’s Conspiracy.
                      Andy Gordon.
                      Andy Grant’s Pluck.
                      Bob Burton.
                      Bound to Rise.
                      Brave and Bold.
                      Cash Boy.
                      Chester Rand.
                      Do and Dare.
                      Driven from Home.
                      Erie Train Boy.
                      Facing the World.
                      Five Hundred Dollars.
                      Frank’s Campaign.
                      Grit.
                      Hector’s Inheritance.
                      Helping Himself.
                      Herbert Carter’s Legacy.
                      In a New World.
                      Jack’s Ward.
                      Jed, the Poor House Boy.
                      Joe’s Luck.
                      Julius, the Street Boy.
                      Luke Walton.
                      Making His Way.
                      Mark Mason.
                      Only an Irish Boy.
                      Paul, the Peddler.
                      Phil, the Fiddler.
                      Ralph Raymond’s Heir.
                      Risen from the Ranks.
                      Sam’s Chance.
                      Shifting for Himself.
                      Sink or Swim.
                      Slow and Sure.
                      Store Boy.
                      Strive and Succeed.
                      Strong and Steady.
                      Struggling Upward.
                      Tin Box.
                      Tom, the Bootblack.
                      Tony, the Tramp.
                      Try and Trust.
                      Wait and Hope.
                      Walter Sherwood’s Probation.
                      Young Acrobat.
                      Young Adventurer.
                      Young Outlaw.
                      Young Salesman.

Any of these books will be mailed upon receipt of =35c., or three
copies for $1.00=. Do not fail to procure one or more of these famous
volumes.

       =A Complete Catalogue of Books Will Be Sent Upon Request.=

                   HURST & CO., Publishers, NEW YORK.

------------------------------------------------------------------------

                             =HENTY SERIES=

An entirely new edition of these famous Books for Boys, by G. A. Henty.
This author has reached the hearts of the younger generation by
cleverly amalgamating historical events into interesting stories. Every
book illustrated. 42 titles. Price, 35c.

                  ------------------------------------


        Among Malay Pirates. A Story of Adventure and Peril.

        Bonnie Prince Charlie. A Tale of Fontenoy and Culloden.

        Boy Knight, The. A Tale of the Crusades.

        Bravest of the Brave, The. With Peterborough in Spain.

        By England’s Aid; or, The Freeing of the Netherlands
        (1585-1604).

        By Pike and Dyke. A Tale of the Rise of the Dutch Republic.

        By Right of Conquest; or With Cortez in Mexico.

        By Sheer Pluck. A Tale of the Ashanti War.

        Captain Bayley’s Heir. A Tale of the Gold Fields of California.

        Cat of Bubastes, The. A Story of Ancient Egypt.

        Cornet of Horse, The. A Tale of Marlborough’s Wars.

        Dragon and the Raven; or, The Days of King Alfred.

        Facing Death. A Tale of the Coal Mines.

        Final Reckoning, A. A Tale of Bush Life in Australia.

        For Name and Fame; or, Through Afghan Passes.

        For the Temple. A Tale of the Fall of Jerusalem.

        Friends, Though Divided. A Tale of the Civil War in England.

        Golden Canon, The.

        In Freedom’s Cause. A Story of Wallace and Bruce.

        In the Reign of Terror. Adventures of a Westminster Boy.

        In Times of Peril. A Tale of India.

        Jack Archer. A Tale of the Crimea.

        Lion of St. Mark, The. A Story of Venice in the Fourteenth
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        Lost Heir, The.

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        Orange and Green. A Tale of the Boyne and Limerick.

        Out on the Pampas. A Tale of South America.

        St. George for England. A Tale of Cressy and Poitiers.

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        True to the Old Flag. A Tale of the American War of
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        Young Buglers, The. A Tale of the Peninsular War.

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        Young Colonists, The. A Story of Life and War in South Africa.

        Young Franc-Tireurs, The. A Tale of the Franco-Prussian War.

        Young Midshipman, The. A Tale of the Siege of Alexandria.


                  ------------------------------------

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        SUCCESS AND ITS ACHIEVERS.

        TACT, PUSH AND PRINCIPLE.

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We publish six of his best.


=CAMPING OUT=
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        ALL ABOARD; or, Life on the Lake.
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        THE YANKEE MIDDY; or, The Adventures of a Naval Officer.
        YOUNG LIEUTENANT; or, The Adventures of an Army Officer.

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------------------------------------------------------------------------




Transcriber's note:

  Inconsistencies in capitalization of the name "Ding-Dong"
  vs "Ding-dong" have been left as is.

  Several pages of ads are duplicated in the original text; they
  have been left as is.

  page 72 - moved apostrophe in "Ranger's"
  ...changing the course of the Motor Rangers' vessel.

  page 82 - changed period to comma at end of quote
  I’ve got an idea." said...

  page 83 - capitalized sentence
  ...said Mr. Tubbs. "we haven’t got any weapons, and those rascals...

  page 110 - added comma at end of speech
  ...when you see it flying in a foreign port" observed...

  page 120 - added period to chapter title to be consistent
  the other chapter titles
  XIII. "SOUTH AMERICAN JUSTICE"

  page 163 - changed "inqury" to "inquiry"
  ...to the professor’s inqury.

  page 171 - changed "head-gear" to "headgear" to be consistent
  with other usage in this book

  page 249 - added "in" after "candle"
  ...pocket lantern here, too, with a candle it. Shall...

  page 256 - changed "It" to "If"
  It you don’t get me...

  page 275 - changed "awe-struck" to "awestruck" to be consistent
  with other usage in this book
  ...Nat, in awe-struck tones...


  page 281 - changed "Zepplein" to "Zeppelin"

  page 284 - changed "Macto" to "Matco"
  ...the boys. Old Macto received a substantial...

  no page number - "Molly Brown Series" advertisement
  changed "sophmore" to "sophomore"

  no page number - "Girl Aviators Series" advertisement
  changed "terrestial" to "terrestrial"
  ...many stumbling-blocks in their terrestial path, but they...

  no page number - "Girl Aviators Series" advertisement
  changed "abiltity" to "ability"
  ...the mechanical power implied by “motor,” the abiltity to...

  no page number - "The Famous Alger Books"
  changed comma to period
  ...Sam’s Chance,...

  no page number - "The Dreadnought Boys"
  changed "Areo" to "Aero"
  Among the volunteers accepted for Areo Service are Ned...

*** END OF THE PROJECT GUTENBERG EBOOK 48270 ***