THE BOY AVIATORS IN AFRICA

OR

AN AERIAL IVORY TRAIL

By Captain Wilbur Lawton

CONTENTS

I [A REUNION]
II [THE STOLEN IVORY]
III [THE DARK CONTINENT]
IV [THE WITCH-DOCTOR]
V [THE POOL OF DEATH]
VI [A SNAP-SHOT FIEND IN TROUBLE]
VII [A TRAITOR IN CAMP]
VIII [A BATTLE IN THE AIR]
IX [THE VOICE OF THE MOUNTAIN]
X [THE ARAB'S CACHE]
XI [THE AGE OF SIKASO]
XII [IN THE HANDS OF SLAVE-TRADERS]
XIII [GORILLAS—AND AN AERIAL TOW-LINE]
XIV [AN ESCAPE—AND WHAT CAME OF IT]
XV [THE FLYING MEN]
XVI [FOOLING AN ARAB CHIEF]
XVII [THE "ROGUE" ELEPHANT]
XVIII [A LINK FROM THE PAST]
XIX [FRIENDS IN NEED]
XX [THE SMOKE READER]
XXI [THE CHUMS RESCUED BY AEROPLANE]
XXII [LUTHER BARR'S TRICK]
XXIII [ABOARD "THE BRIGAND"]
XXIV [THE BOY AVIATORS HOLD A WINNING HAND]

CHAPTER I

A REUNION

"Here, Harry, catch hold."

"Ouch—I dropped that cartridge box on my pet corn."

"Say, you fellows, are we going to Africa or are we on a Coney Island picnic?"

"Be serious now, Billy Barnes, you may be all right as a reporter, but as a shipping clerk you're no more good than a cold storage egg."

"Well, I'm doing the best I can," was the indignant reply, "here—I've got it all down: Box 10— One waterproof tent, one rubber-blanket, tent-pegs, ropes, more ropes.—Say, Frank, what in the name of the 'London Times' and jumping horn-toads do you want so much rope for?"

"To tie up a certain young reporter named William Barnes when he gets too fresh," was the laughing reply.

The three boys sat about a heaped, confused collection of ammunition, cooking-utensils, rifles, and camp "duffle" in general, one evening late in May. The eldest of the group, a sunny-faced, clear eyed lad of about sixteen, held in his hand a notebook from which he called out the inventory of the articles piled about him as his brother, a youth of fourteen, sorted them out. The third member of the trio was a short, stocky chap of possibly seventeen, with sharp, blue eyes that gleamed behind a pair of huge spectacles. He was examining a camera with care; from time to time turning his attention to an open notebook that lay beside him in which he was supposed to be entering the list as the other called it off.

The place where the boys were busying themselves was the upper floor of a large garage in the rear of the Chester residence, on Madison Avenue, New York City, which had been turned into a workshop for the two young Chesters—Frank and Harry—already well known to our readers as The Boy Aviators. The well set-up lad who was so industriously calling off the equipment that lay scattered about was Frank Chester, and the ready classifier of the mixed-up outfit was Harry, his younger brother. The third member of the group was Billy Barnes, the young reporter, already down to us as the chronicler of the Chester boys' adventures in Nicaragua and the depths of the Everglades of Florida. Since the boys' return from Florida on the U. S. torpedo boat, the Tarantula, they had been busy putting into shape the rough working plans of the African hunting expedition they had planned as a sort of vacation.

The ample bonus the government had awarded them for their singularly clever work in rescuing Lieutenant Chapin, the inventor of Chapinite, by their aeroplane Golden Eagle II, had supplied them with ample funds for their trip. As for Billy Barnes (or "Our Special Staff Correspondent, William Barnes," as he was now known), besides the sum realized from the sale of the rubies the boys found in the Quesal Cave in Nicaragua, the money the youthful scribe had made on writing up the boys' Florida adventures had provided him with a good fat nest-egg.

The natural stimulus given to the red-blooded Chester boys by Mr. Roosevelt's hunting adventures had a good deal to do, with their resolution to go to Africa. And now—after several weeks of work on getting together as good an outfit as was procurable—they were putting what Billy called "the finishing touches" on their accoutrements. Stacked in corners of the room were big chests painted blue and marked with the boys' names and neatly numbered in white painted characters. These cases contained the different sections of the Golden Eagle II, the aeroplane equipped with wireless, that had made history in Florida.

There were twenty of these cases besides the ones labeled "Camp Outfit," "Medical," "Armory Chest," "Grub Chest," and several nondescript ones containing the odds and ends that an expedition of the kind they planned would find indispensable. In some smaller boxes also were packed yards and yards of bright-colored cloth and calico, spangles, cheap jewelry and brass ornaments for use among the natives. In making up their outfit the boys had taken the advice of a well-known African traveler who had retired from his adventurous life to purchase a place in New Jersey, where he intended to spend his remain days. Through a mutual friend the boys obtained an introduction to him and his advice in selecting the outfit had been simply invaluable.

"Go easy, carry lots of quinine, don't waste ammunition, and count ten before you pick a quarrel with a native," had been his simply laid-down rules for getting along in Africa, and these rules the boys had determined to adhere to strictly.

"Say, is this going to be a hunting trip or an invasion of Africa?" inquired Billy, quizzically as Harry sorted out and Frank read off ceaselessly the apparently interminable inventory of the supplies of the Chester party. "I'm getting writer's cramp."

"A hunting party of course," laughed Frank, "but you know that hunters who go into the bush depending on their rifles usually come out a good deal thinner than when they went in.

"That's so," assented Billy, "but when we have a sixty-mile aeroplane like the Golden Eagle II we can easily fly out to civilization in case of necessity."

"Yes, if we have enough gasoline," assented Harry, "but how much can we carry into the bush?"

"Just enough for our purposes and no more," replied Frank, readily, "fortunately the soluble tablets of picric and glycerine will help out our supply materially. A few of these tablets dissolved in gasoline render the efficiency of one ordinary gallon equal to three; but I don't care to use them except in a case of absolute necessity as they are very hard on an engine."

"Then we can count on every gallon we carry being of triple efficiency?" asked Billy.

"Certainly," replied Frank, who had invented the tablets in question, and which were an extremely useful addition to the equipment of the modern aviator. As the boys worked on and the equipment, as it was classified, was packed away in the cases assigned to each class of articles, there came a sharp knock at the door of the garage building and a servant entered with a special delivery letter to Frank. The boy tore it open eagerly and then gave a low whistle of astonishment.

"Read it out, Harry," he said, handing the missive to his brother. "It concerns all of us."

Harry took it and read as follows:

DEAR FRANK AND HARRY:

Shall be in town to-morrow morning with my father and Mr. Luther Barr, the well-known ivory importer. He has a communication of importance for you. What it is I am afraid to trust to writing, but you will know full details when you see us. Will you call at the Waldorf at ten-thirty and have breakfast? We can discuss the matter over the meal. All I can say now is that if the Golden Eagle is still in shape for her old-time stunts there is work ahead of her that will prove harder than anything she has yet tackled. However, I know you are not the chaps to balk at a little danger—particularly when exciting adventures are in the wind.

So long, then, till to-morrow:

"LATHROP EASLEY"

"Well, what do you know about that?" gasped Billy Barnes, "here we are fixing up for a nice little holiday trip to rest our shattered nerves, and here comes, a job along that looks as if we should have to work all summer."

"It certainly is curious," replied Frank musingly.

"What can Lathrop mean? Who is Luther Barr? I have heard the name but I cannot place him."

"Lathrop says he is an ivory importer," suggested Harry.

"Easy to find out," said the resourceful Billy. "Where's the 'phone book?"

Frank handed the volume to him from its hook beside the instrument.

"Ah—here we are," exclaimed Billy, as he ran his finger triumphantly down the "B" list. "Barr, Luther—that's our man, eh? Ivory importer, offices No. 42 Wall Street—home, White Plains."

"White Plains, that's where Lathrop's folks live," exclaimed Harry. "That's where he first became associated with the Golden Eagle."

"And turned out to be a good partner," added Frank.

"A jim dandy," agreed Billy. "I tell you boys, I've got a good nose for news and if there isn't some sort of a story back of Mr. Luther Barr and Lathrop's letter I'll eat my hat without sauce."

Any acceptance of the young reporter's generous offer was interrupted by a sudden noise in the usually quiet street.

"I tell you the fare's a dollar!" the boys heard an angry voice declaim.

"'Tain't nothing of the kind or I'm a lubber—fifty cents is all I'll pay. I'll be horn-swoggled if you get a cent more, yer deep-sea pirate," was the indignant phrased reply.

Something in the voice was strangely familiar but the "horn-swoggled" settled it.

"Ben Stubbs," gasped all the boys simultaneously and rushed out of the garage to the street.

Here they found a stoutly-built, crisp-bearded man with a face tanned to what Billy called a "weathered oak finish," arguing loudly with a taxicab chauffeur. The man was obdurate over his fare and just at, the boys came on the scene was suggesting that his equally determined passenger get back in the cab and take a ride to the police station.

"The sergeant will settle our dispute," he said angrily.

"What's the trouble, Ben?" exclaimed Frank, giving the angry man on the pavement a hearty slap on the back.

"Why, this here piratical craft," the other was beginning when suddenly he dropped the battered bag he carried and burst into a mighty roar—a regular Cape Horn hail.

"Back my topsails if it ain't you, Frank," he cried, wringing the other's hands till the boy's arms were almost dislocated. "And you too, Harry, and keel haul me ef here ain't Billy too. Well, if it ain't good to see, you Chester boys again."

"Say, are you the Chester Boys—the Boy Aviators?" suddenly cut in the chauffeur in a respectful tone.

"We are," replied Frank, "why?"

"Oh, well," said the chauffeur, "then I'll let your friend off with fifty cents. I thought he was a 'greeny'."

With that, he calmly twisted the dial of the cab which registered $1.00 back to the fifty cent mark and coolly pocketed the coin the indignant Ben handed.

"Does that thing work backwards?" demanded the amazed old adventurer, as the taxi whizzed off before he could frame words to express his indignation.

"Not often," replied Billy with a laugh. "I guess that chap reads the papers and thought it wouldn't do him any good to try to fool a particular friend of the Boy Aviators."

"Well, boys, what are your plans?" demanded Ben, as—after the rugged fellow had been introduced to Mrs. Chester, a sweet-faced old lady, and Mr. Chester, a fine-looking, gray-haired man of about fifty—he and the boys sat in the garage discussing the African outfit.

"We hardly know now," replied Frank, and then in a few words he described Lathrop's letter and its contents.

"Wherever that boy is there's bound to be doings," remarked Ben, sententiously, when the young leader had finished. "Down in Florida when he wasn't tumbling into alligators' mouths or getting bit by serpents he was allers up to some mischief—you mark my words there's something in the wind now."

The boys talked late and long that night over the letter and what possible plan Mr. Barr, the ivory importer, could have to discuss that would be of interest to them, but they were able to arrive at no definite conclusion except that there was nothing to be done about it till morning.

As for Ben with his usual philosophic attitude toward mysteries, he filled his pipe and silently smoked. To those of our readers who have not met Ben this phase of his character may seem inexplicable, but to the boys Ben's passive acceptance of any situation had become quite familiar. Ever since they had rescued the rugged old adventurer from a marooned treasure-mine in Nicaragua and he had shared their strange adventures in Florida on the Chapin Rescue Expedition, the old man had become as much a part of their necessary equipment as the Golden Eagle itself. He had arrived that night in response to a telegraphed request to his cottage at Amityville on Long Island, where he cultivated an extensive farm—also part of the Quesal ruby profits—and devoted himself to fishing and hunting.

'The Boys' mere word, however, that they were off to Africa had been sufficient to arouse the old man's roving instinct and here he was on deck once more as active as a boy and almost as impatient for the start for the Dark Continent. Ben slept at the Chester's home that night and if his dreams were not as populated with visions of elephants, leopards, deer, huge snakes and pigmy savages as theirs it was not any lack of interest in the coming expedition that was responsible for it.

CHAPTER II

THE STOLEN IVORY

"Will you please send this card up to Mr. Beasley's rooms and tell him that the visitors he was expecting are here?"

It was Frank Chester who spoke early the next day, as the boys, in response to Lathrop's letter, stood at the Waldorf desk. The clerk looked at them a little disdainfully. Frank and Harry Chester were not the sort of boys who devoted much time to thinking about clothes and while they both wore dark neat-fitting suits they certainly did look a little out of place among the pasty-faced, cigarette-smoking youths in loud-looking garments who constituted most of the young men with whom the clerk was in the habit of coming in contact.

"I don't think that Mr. Beasley can see you now, call later," he began, superciliously turning round to the letter-rack and sorting out the mail and putting each guest's letters in the proper box.

For a second an angry flush rose to Frank's face. The man's manner was enough to irritate any high spirited boy. But Frank Chester was not given to what Bill Barnes called "flying off the handle." He calmly took another card from his pocket and in a rather sharp voice, though his tones were even enough said:

"Are you going to send that card up at once or shall I call the room on the telephone?"

The clerk faced quickly about. The two youths he had looked upon as rather awkward country bumpkins, judging as he did from their tanned faces and broad shoulders, were evidently not to be trifled with. He glanced at the card as he rolled it up and handed it to a boy to be placed in a pneumatic tube and shot up to the fourth floor, on which Mr. Beasley and his party had taken rooms.

"Oh, you are the Chester boys?" he exclaimed with a strong accent on the "the" and in markedly more respectful tones.

"We are," said Frank with a smile which was reflected on his brother's face.

"I beg your pardon for keeping you waiting, I'm sure," said the clerk with an apologetic leer, meant to be an engaging smile.

"That's all right," said Frank shortly, turning away from the desk.

"Well, having your name in the paper does do you some good after all," remarked Harry with a laugh. "That fellow certainly turned a flip-flop, when he found out who we were."

Five minutes later the boys were ushered into the Beasley rooms and were busily engaged shaking hands and exchanging all sorts of boyish exclamations of welcome with Lathrop Beasley, a tall, rather slender youth who had been their companion in Florida. Like the boys, Lathrop was an accomplished aviator and wireless operator, although he had not the initiative or the sturdy pluck to perform the feats that they had. He was, however, a boy of considerable brain and skill and among the boy-aviators of the country held an enviable position.

"About your letter," began Frank when the first greetings were over.

"In a minute," replied Lathrop, "here's father now."

As he spoke, the portieres parted and a stout, fresh complexioned gentleman, ruddy from his bath and shaving, appeared. He had the pompous manner of the successful man of business and seemed to the Chester boys to be the least bit patronizing in his manner.

"Mr. Barr will be here in a minute," he said, after introductions had been made by Lathrop, "he will explain to you his idea. I am merely a partner in the enterprise. You will, of course, be glad to accept any restrictions he may impose?"

"We hardly care to discuss that yet," said Frank, rather nettled by Mr. Beasley's pompous manner, "until we know what he requires." He exchanged glances with Harry.

"In fact," he went on, "we were planning to take a complete rest and follow in Mr. Roosevelt's foot-steps, by taking a hunting trip in Africa, only," he added with a smile, "we meant to hunt by aeroplane."

"Wonderful," said Mr. Beasley, evidently much impressed by Frank's ready manner, "when I was a boy, if a lad had a "bone-shaker" bicycle he thought he was doing something fine, and as for flying—why, we never thought of it."

"Perhaps the boys of to-day are further sighted," said Frank with quiet note of sarcasm in his tone that was quite lost on the well-meaning old merchant. Indeed at that moment Mr. Beasley rose heavily from his chair and stepped forward to greet a new arrival who appeared from another room of the suite.

"This is Mr. Luther Barr, the famous ivory importer," he said, with far more respect in his tones than he had used to the boys; whom indeed, he looked upon as talented chaps, but still boys—which to men of his caliber is an infallible sign that anything such youthful persons may attempt is extremely likely to go wrong. How erroneous such an opinion is, those of our readers who have followed the adventures of the Chester boys know.

Mr. Luther Barr deserves a new paragraph. Long, lean and hollow cheeked, the term "gangling" fits him better than any other. Mr. Luther Barr's black suit hung on him as baggily as the garments of a cornfield scarecrow and Mr. Luther Barr's sharp features were not improved by a small growth of gray hair; of the kind known as a "goatee" that sprouted from his lower rip. For the rest of the boys noticed that Mr. Barr was gifted with a singularly gimlet-like pair of steely blue eyes that seemed to bore through you.

"As sharp a man as ever drove up the price of ivory," added Mr. Beasley as he introduced the boys to this singular figure, "he can scent an ivory bargain—"

"From here to Africa," struck in Mr. Barr in a sharp nasal tone that grated unpleasantly, "and you and I are going to be Kings of Wall Street if these boys put this deal through for us," he added with what was meant to be an amiable smile, but which, as a matter of fact, distorted his face till it looked uncommonly like an old Japanese war mask. Indeed the boys, who had seen the collection in the Metropolitan Museum, could not help smiling to themselves, as the same thought struck each of them.

"Well, Beasley," exclaimed Barr suddenly, "I'm as sharp set as a Long Island fox. Let's have a bite of breakfast and then we can get down to business."

From Mr. Barr's manner of dispatching his breakfast and the remarkable skill with which he wielded his knife, in conveying various morsels to his mouth, it was evident that he had spent so much time piling up money that his social education had been sadly neglected. Once or twice the boys caught Lathrop's eye and they saw that the lad was blushing with shame at the uncouth manners of his father's friend. For this reason the boys refrained from paying any apparent attention to Mr. Barr's actions, although—as, they remarked afterwards—he was as well worth watching as the "sword swallower in a circus side show."

"Yes, boys," said Mr. Barr with his mouth full of buttered toast and ham and eggs, "I guess I know more about Africa than any man alive."

"You have crossed that continent?" asked Frank..

"No, sir," replied the old ivory merchant with some contempt. "I wouldn't waste my time where there ain't no ain't no money. What I mean is, I know more about the Gold Coast, the Ivory Coast and the Slave Coast than any man in this or any other country and have got more good solid coin out of them."

Mr. Beasley looked up admiringly from his plate. Here was evidently a man after his own heart.

"The Slave Coast?" echoed Harry inquiringly, "I thought—"

"Thought there wasn't no more slaves, eh?" inquired Mr. Barr amiably, swallowing his coffee with a noise like water running out of a bath tub, "wall, that's because yer young. When yer git older you'll larn that there's money in everything here's a demand for, and there's just as big a demand for slaves on some rubber plantations I could tell yer of as there ever was in the old days of the South—and more money in 'em on account of its being more dangerouser."

"Do you mean to say that there is slave-running now?" asked Mr. Beasley, while both Frank and Harry wondered and Lathrop looked uncomfortable.

"Sure I do," chirped Mr. Barr, "but no more for me. There's too many British gunboats and 'Merican gunboats and Dutch gunboats and what not about now to make it comfortable or healthy. No, I've retired from that business—but there's money in it," he concluded with a regretful sigh.

Immediately Mr. Barr had concluded his breakfast—and with his apparently slim accommodations it was a wonder to the boys where he put it all—he snapped, with a flinty glint of his small pig-like eyes:

"Now, let's git down to business. You boys want ter make a bit of money?"

"'To be sure we do," replied Frank, "but we don't want to make any that isn't honest money."

"We'll, there's no accounting for boys nowadays," sighed Mr. Barr, "however, you needn't worry about this money—there'll be plenty of it and it'll all be good honest coin."

"What do you wish us to do?" demanded Frank.

"Just this: Mr. Beasley here and me is in on a deal in ivory. That is, we were, but the big cache we had hoarded up in the Kuroworo Mountains in the Bambara country has been stolen by a rival trader, an Arab named Muley-Hassan. We know where he's hidden it and we know, too, that he won't dare to bring it out till he thinks that we aren't watching him. Now the time is ripe for a big deal in Ivory. There is a shortage in the market. Prices will go up sky high. If we get it out in time we'll make a barrel of coin, but if we don't we stand to lose heavily."

Mr. Beasley gave a groan; to the boys' amazement he seemed to be about to collapse. Lathrop too looked ill and anxious. Old Barr paid no attention, however, but went on.

"Now, I heard about you boys and your air-ship, and I heard, too, that you was planning a little trip to Africa and thought you might like to combine business and pleasure."

He drew from his pocket a much-thumbed, crudely drawn map and spread it out on the table. How he obtained it, the boys never learned exactly, but they heard later that a treacherous attendant of the ivory dealer had sold it to him for a good round sum.

"This country down here," he said, indicating it with a black rimmed finger nail, "is the Southern Soudan. Here's the Bambara country to the north of Uasule. Now right at this point, in the Moon Mountain range,"—he pointed to a red-marked trail zigzagging across the map to the range and terminating in a red star—"right at that thar point, old Muley-Hassan, the Arab, has hidden our ivory cache. You see the latitude and longitude is marked and furthermore—and here's the most remarkable part of it—you will know the spot when you see it by the fact that the mountains above the cache present an exact facsimile of an upturned human face. In a direct line drawn from the nose of this face, where you see the red star, lies the ivory."

The boys were deeply interested. Unpleasant as was the impression old Barr had made on them, yet what he was disclosing was impressive; but as yet they did not show that they were anything more than casually struck by it.

"Well, Mr. Barr?" said Frank, as the old matt paused impressively.

"Well—" said Mr. Barr, "the scoundrel stole it and it's up to you to get it out of there, if you will undertake it."

"How does it depend on us?" asked Frank.

"In just this way. Muley-Hassan has his eye on us—-we can do nothing toward locating the ivory. You can pitch a camp there and scout about for it in your aeroplane or dirigible or whatever you call it."

"But even if we do find the Arab's hiding-place, what good does that do?" objected Frank.

"We can arrange with the French government to send soldiers up into the country and get the stuff out, if necessary," readily replied the wrinkled old ivory dealer, "but we can make no move till the cave is located. If they suspected we were after it, they would soon move it to another hiding-place or even pack it cross-country to the Nile and ship it out by the Mediterranean."

Frank and Harry asked leave to hold a brief consultation at the conclusion of which, they announced that they would think the matter over, and see Mr. Barr at his office the next day. The old man was far too shrewd to insist on a decision then and there, and so he left the hotel with the boys' promise to consider the matter carefully. As for Frank and Harry, they had pretty well made up their minds not to have anything to do with Mr. Barr, but an unforeseen circumstance altered their determination. As Barr left the room with Mr. Beasley, Lathrop turned on them with troubled eyes.

"Will you do it, Frank?" he asked anxiously. "Please say yes."

"Why, Lathrop, whatever is the matter," asked Harry, noticing the almost painful anxiety, with which the boy looked at Frank and hung on his decision.

"It's just this," said the boy in a voice that shook, as he tried to steady it, "if that ivory isn't found, we shall be ruined. My father will be beggared."

"Beggared," exclaimed both the Boy Aviators who had regarded Mr. Beasley—as indeed did his friends in general—as one of the "best fixed" business men in New York.

"It's true,"' said Lathrop, despairingly. "He has been speculating foolishly and entered into an agreement with this man Barr to borrow money for still further stock deals. The only hope he has of paying his debts is the realization of the profits he could have made on the ivory. Its theft was a bitter blow to him, not so much for his own sake, as for my mother and sisters. Myself I don't care, I can get out and work, but it would break my heart to see them reduced to poverty."

The situation was a difficult one for the Chester Boys. They had taken a hearty dislike to the crafty old ivory merchant and had made up their minds not to enter into any enterprise in which he was interested. Here, however, was a new complication.

"Give us half-an-hour, Lathrop," said Frank at length, and the two boys withdrew to another room to talk the matter over. It was ten minutes past the agreed time when they came back.

In the meantime Lathrop had been joined by his father and the two had waited in painful anticipation for the Boy Aviators' verdict.

"Well—," began Lathrop eagerly as the two boys with grave faces reentered the room.

"Well," said Frank, with a smile, "I guess we'll help you out, Lath."

Tears stood in the eyes of both Mr. Beasley and his son, as in shaky voices they endeavored to thank the Chester Boys.

"That's all right, Lathrop," said Frank at length—"turn about's fair play. You drove the aeroplane to Bellman's island you remember and saved us—now, we'll save you and your father, if we can—how long can you give us, Mr. Beasley?" he asked, briskly turning to the thoroughly humbled merchant.

"Eight weeks—if I hear from you by cable in eight weeks I can keep things going," was the reply.

"Phew!" whistled Frank, "that's not an awful lot of time."

"Can you do it, Frank?" asked Lathrop eagerly.

"We'll try as hard as we know how," was the modest answer.

"And—and you'll take me along?" faltered Lathrop.

"Sure, you can come as your father's representative at large," laughed Frank.

CHAPTER III

THE DARK CONTINENT

About a month after the events related in the last chapter the bluff-bowed French coasting steamer, Admiral Dupont, dropped anchor in the shallow roadstead off the steamy harbor of Fort Assini on the far-famed Ivory Coast. A few days before, the boys had left Sierra Leone and engaged quarters on the cockroach-infested little craft for the voyage down the coast. It was blisteringly hot and from off the shore there was borne on the wind the peculiar smell that every traveler knows as "African." It is the essence of the dark continent. Our young voyagers and Ben sniffed at it eagerly.

"Smells like marigolds," said Billy at last—and it did.

But there was soon plenty more to discuss than the strange appearance of the town, which in reality was little more than a big village with here and there one, or two houses of some pretension scattered about. For the rest, it consisted of the wickerwork huts of the natives. Back of the town were dense forests and beyond these again a long blue line of hills. An unhealthful looking lagoon lay between the houses and the mainland, into which the boys had been told the Bia River, up which they were to begin their voyage to the interior, emptied.

A broad yellow beach stretched in front of the houses and from this, as soon as the little steamer dropped anchor, whaleboats and canoes in great numbers were launched through what looked to be a thunderous surf. They were navigated by Kroomen—or Krooboys as they are sometimes called—and who are a superior race to most of the natives of Africa.

Some of the paddlers and oarsmen in the boats that surrounded the Admiral Dupont were almost six feet in height and splendidly built.

"Good looking fellows those," said the captain, who had joined the group of wondering young adventurers, "but in spite of their good looks they are petty thieves, if they get the chance."

Of this quality, the boys were soon to get an example. Frank had laid down his field-glasses on a deck chair and didn't give them any more thought, even when the decks were fairly swarming with half-naked, chattering, laughing Kroomen. When he looked around for them, however, for the purpose of making out more clearly the outline of the distant mountains, the glasses had vanished.

The young leader quickly divined what had occurred and stepping to the rail he held above his head an English sovereign and a pair of glasses, borrowed, from Billy.

"I'll give this money to the man who finds my field glasses," he shouted.

"It's a long chance," he remarked to Harry, "there may be some one there who understands English. Anyway they can see that I'm willing to give money for something like the object I held up."

As much to Frank's astonishment as anyone else the next minute they heard a hail from a canoe containing two particularly black Kroomen.

"Hey, boss;" one of them was shouting, "what you lost, eh?"

"Some one stole my field-glasses," shouted back Frank.

"All right, American massa," hailed back the Krooman, "I sail long time 'Merican ships. I catch him for you."

"Well, what do you think of that?" demanded Billy. "If the Statue of Liberty had come off her perch and done a song and dance you couldn't have astonished me more than to hear that sack of coal talk English."

"They take several of those fellows to sea on trading ships, that stop in here for logs from the interior," struck in Ben. "It wouldn't surprise me but what that fellow there has been in New York harbor, yes, and in San Francisco too."

The boys looked their astonishment.

"They are good hard workers," went on Ben, "and make good sailormen. They always come back here though in the end. They are as home loving as a house cat."'

While the boys talked, their baggage was being hoisted into a lighter that lay alongside, ready for shipment ashore. They were about ready to quit the ship when their attention was attracted by a terrific uproar among the natives alongside. Two or three canoes had been upset and in the water half a dozen Kroomen were splashing about like big, black fish.

"They'll drown," gasped Harry, as he watched the furious water battle.

"Not them," sniffed Ben, "they are as much at home in the water as they are ashore. Hello!" he exclaimed, suddenly pointing, "there's your field-glasses again, Frank."

Sure enough, from the hands of a spluttering, half-drowned native, the Krooman who spoke English had just wrested a dripping pair of black morocco-covered field-glasses. He held them aloft in triumph, treading water while he held the other's head under the sea as a punishment for his thievery.

"I catch 'um, boss, I catch um," he kept shouting triumphantly. A few seconds later, having half drowned the unfortunate thief, he stood dripping like a figure cut out of black basalt before the boy. As he received his recovered property Frank presented its rescuer with the sovereign. If it had been a fortune the man could not have been more overcome with gratitude. He sank on his knees.

"You come ashore my boat?" he begged. "Cost nothing to United States boys."

The adventurers assented and, having seen their baggage properly stowed on the lighter, they landed through the surf a short time later and found themselves on the flat, yellow beach facing the rather dreary looking row of Europeans' houses. The method of landing the surf boats and the wonderful dexterity with which the natives handle them is worth a whole chapter to itself. But it might prove tedious reading, so suffice it to say, that with one man standing erect in the stern with a steering oar, and the others paddling like demons, the Ivory Coast boatmen invariably land their passengers, in a smother of foam which seems overwhelming, without spilling a drop of water on them. Not a visitor to this coast but has been impressed by their wonderful skill.

"Well, here we are," remarked Billy, looking about him at the novel surroundings.

"The first thing to do," announced Frank, "is to go to the house of Monsieur Desplaines, to whom Mr. Barr gave us a letter of introduction, and talk over our plans."

Monsieur Desplaines was the consular agent of the United States government at Assini, which is a French port, and had promised by cable to Mr. Barr to give, the young travelers all the advice that his experiences could suggest. He had also volunteered to select for them a train of native baggage carriers, and hunters that would be reliable. There are no roads into the heart of Africa and everything is transported by human pack-trains. The natives of this part of the coast are strong, muscular men not easily fatigued and are capable of carrying burdens on their heads twenty-five miles or more a day without exhaustion.

As the boys started to make their way up the beach a trim figure with neatly waxed black mustaches, almost extinguished in a huge pith helmet and dressed in white duck with a red sash about the waist, emerged from the nearest house and hastened toward them.

"Welcome to Africa!" cried the newcomer as he approached and who, as Frank at once guessed, was M. Desplaines himself. "Come with me to the house and make yourselves at home."

The boys shook hands warmly with the little Frenchman who seemed so hospitably inclined and followed him eagerly toward the whitewashed house from which he had emerged.

"I would have been at the steamer to meet you," he exclaimed apologetically; "but she got here a day ahead of time and I was not prepared."

Inside the house, which was delightfully cool and darkened by jalousies from the glaring heat outside, the young adventurers were introduced to Madame Desplaines and two little girls, who constituted the family of the consular agent, who also kept the general supply store at Assini.

After dinner that evening, M. Desplaines talked long and earnestly to the boys. Of the real object of their mission, he had of course no knowledge. That was kept a secret even from Barr's intimates. There was too much at stake to let it leak out. His idea was the boys had come on a hunting and exploration, much of which was to be performed by aeroplane. He informed the boys that, acting on cabled instructions, he had laid in a good supply of gasoline by the last steamer from Sierra Leone and that arrangements for a train of carriers and for boats up the river had been made. There was a wheezy steam launch belonging to the trading post which would tow the boats up the Bia River as far as they desired. The Kroomen the boys engaged would take them to that point would then be abandoned, as they refused to go far from the coast. Such was the outline of M. Desplaines' conversation with the travelers.

The evening was far advanced when already the little party was ready for bed and already their imaginations had been fired by the tales that the consular agent had told them of the interior of the wild Bambara country. As they were saying good night to their hospitable host and hostess, there was a knock at the door. In response to M. Desplaines shouted: "Come in," a tall coal-black figure stalked into the lamp-light. The glow shone warmly on his black skin and lit up the mighty muscles that played beneath it. The strength of the man was evidently tremendous. The boys, to their surprise, recognized him at once, as the rescuer of Frank's opera-glasses. He paid no attention to Desplaines or his family, but walked straight up to Frank.

"Hi boss, you go hunt, you go far into land of Bambara," he said, raising his mighty arm and pointing to the northeast.

Frank nodded.

It was a strange scene. The boys and Ben in their hunting costumes and stout boots, M. Desplaines, short and inclined to be fat and as neatly barbered and tailored as if he had just stepped off the boulevards, Madame Desplaines and her little girls in cool, white frocks—and in the center of the group—dominating it by his impressive manner and mighty form—the huge, ebony Krooman.

"In the land of Bambara much game," went on the Krooman.

"So we have heard," replied Frank.

"In the land of Bambara much danger," continued the Krooman, fixing his dark eyes full on Frank, "much danger to the white boys, who fly like birds."

"Why, how do you know that?" exclaimed Frank, amazed that the Krooman should not only know their destination—which might have been a guess—but have divined the fact that they had an aeroplane.

"Krooman know much that white man not know!" replied the giant black.

Then, rising his finger, he counted the amazed group of adventurers who stood transfixed at the scene.

"One—two—three—four—five go to Bambara," he intoned. "Come back one—two—three. Two die. Sikaso, know."

Before any of the astounded party could frame a question or open their lips, the huge figure had stalked to the doorway and vanished.

"He'd make a nice, comfortable house-pet that fellow," said Billy, who was the first to speak. "One, two, three, four, five go to Bambara," he mimicked. "Come back one, two, three. Two die. Sikaso know. Br-r-r-r-r, he gives me the creeps."

They all laughed at Billy's absurd aping of the stately negro, but nevertheless none of them felt inclined for more talk that night. Somehow, the Krooman had cast a gloom on the party. Had they known how nearly his prophecy was to come to fulfillment they might even have been tempted to abandon the expedition.

CHAPTER IV

THE WITCH-DOCTOR

Bright and early the next day Frank and Harry were up and stirring, and the other members of the party were not long in joining them. The almost innumerable packing cases and chests containing the duffle, ammunition, armament and the sections of the Golden Eagle were scattered about the little "compound" or garden of M. Desplaines' residence, having been brought ashore overnight by a crew of Kroomen. M. Desplaines appeared while the boys were still contemplating their outfit and wondering if it would be possible to accommodate it all in the little flotilla which, it had been arranged previously, was to take them up the river to the camping place from which they were to strike out for the Ivory Mountain.

"I really almost envy your trip," he said, "although it will be fraught with danger. Still you go well armed and provisioned, and from what I have heard of you, you are not the sort of boys to let a few obstacles upset you."

While they were still talking and waiting for breakfast to be announced they were joined by a singular figure. It was that of a white man in rather shabby ducks and crowned, as was M. Desplaines, with a huge, white pith helmet. Over one shoulder he carried a green butterfly net and under one arm he had tucked a tin box. Round his waist was a leather belt from which hung, in addition to a revolver and cartridges, a glass bottle with a wide stopper with a chloroformed sponge reposing in the bottom. It did not need the introduction of the newcomer by M. Desplaines as Professor Ajax Wiseman, to tell the boys that Dr. Wiseman was a naturalist.

"My dear professor, what are you doing here?" exclaimed M. Desplaines as soon as the introductions were over.

"I arrived this morning from Grand Bassam on a coasting schooner," replied the professor, carefully setting down his tin box. "I have a remarkable specimen of the Gladiolus Gorgeosi in there," he remarked importantly. "I am contemplating a trip into the interior via the Bia River and came to you to see if you could arrange transportation."

M. Desplaines looked at the boys.

"These young men have engaged the steam launch, to tow their expedition up the river," he said hesitatingly; "they are going on a hunting trip, into the interior, and have, I venture to say, one of the most complete outfits I have ever seen."

The naturalist looked wistfully at Frank.

"I suppose there would not be the least objection to my availing myself of your assistance in getting up the river," he said, blinking behind his spectacles like an old bat who has unexpectedly emerged into the sunlight. "I have only two canoes and as I carry my own attendant I shall be no trouble."

"We shall be delighted to accommodate you," rejoined Frank heartily, "but I shall have to place one restriction on you. When we reach our destination we must part company as we have work to do of a confidential nature. Our employer, Mr. Barr—"

"Old Luther Barr," burst out Professor Wiseman suddenly.

"Why, yes," rejoined Frank, rather taken aback, "you know him then?"

"I—I have heard of him," replied the other with a slight hesitancy which was, however, so faint as to be hardly noticeable. The voice of Madame Desplaines summoning them to breakfast broke off any opportunity for further questions on a matter that plainly, for some strange reason or other, seemed to have heartily interested—even disturbed—the naturalist. Frank felt troubled for a moment at the idea of having let Professor Wiseman form a portion of their party even for a short distance. But he dismissed the idea almost instantly. The queer expression that passed over Professor Wiseman's face at the mention of the ivory trader's name might have simply been due to astonishment at hearing it again. Still Frank decided to keep an eye on Professor Wiseman.

The conversation at breakfast naturally enough dealt with the little known country the boys were to penetrate. Then it was for the first time that they heard mention of the mysterious tribe of the Flying Men who were reported to be equipped with rudimentary wings—like those of an undeveloped bat with which they managed to flit from tree top to tree top like true flyers.

"Oh, come," laughed Billy, "I've heard of tailed men and white Africans with red top-knots like Lathrop, but a race of winged men is coming it too strong."

"Laugh if you like," declared Professor Wiseman who had brought up the subject, "but some time ago I articulated a skeleton brought me by an Arab slave trader and found extending from the shoulder blade two distinct bony frames which had in life apparently been covered with a thin fleshy substance of leathery like tenacity stretching thence to the wrists. I asked the slave trader where he had found the skeleton," went on the savant, "and he told me he had come across it at the foot of a giant silk cotton tree in the Bambara country."

The boys exchanged glances. It was to the Bambara country—the country of the legendary Flying Men—that they were bound.

"Is any more known of this tribe?" inquired Frank.

"Very little except what you can pick up from the natives, which is little enough," replied Professor Wiseman, "they seem to have a dislike to speaking of the Flying Men—to whites at any rate. I think, too, they fear them. Report has it that they live in cave-like holes in the side of a giant, black basalt cliff reached by a subterranean river. They reach the ground by taking short flights from the holes they live in and regain the cliff dwellings by means of rope ladders formed of twisted creepers."

"Then they cannot fly upward?" asked Frank.

"It would seem not," replied the naturalist, "their wings only serve as gliders. Possibly once in the remote ages they could fly as well as great birds but with the course of the ages and disuse their wings have dwindled."

As may be imagined the idea that within a short time they were to be in the country of the mysterious tribe caused a tremendous stir among the boys and when after breakfast their strange friend of the night before, Sikaso, appeared they at once overwhelmed him with questions. But strangely enough Sikaso made no reply to their eager queries.

He shook his great bead and seemed to be embarrassed, if not by fear at any rate by reticence.

"In Misoto Mountains many strange Ju-jus (fetishes)," he said in an awed tone, "Misoto Mountains no good for white boys—white boys stay away."

"Not much," chimed in Harry, "that's just where we are going."

"You go Misoto Mountain," said the giant black in an astonished tone.

"That's what we are," exclaimed Lathrop.

The black gazed at the ground and drew a small circle on the dust with his toe. In the center of it he made a cross.

"That my dukkeri (fate)," he said slowly, "you go, Sikaso he go too. I see it in the smoke."

"Saw it in the smoke?" repeated the amazed boys.

"In smoke of Ju-ju fire I see it written. I see five go, three come back, in smoke too. I have spoken."

He stalked off as I suddenly as he had the night before and left the boys to gaze in a bewildered way after his huge figure as it swung down the road.

"That fellow's the best disappearer I ever saw," said Billy Barnes at length.

"I wish he'd stop that stuff about 'five go three come back,"' said Lathrop, "it gets on your nerves."

"What could he have meant by seeing it in the smoke?" asked Harry bewilderedly.

"Just this," broke in a quiet voice behind them. It was Professor Wiseman, who had glided up to them as silently as a cat. "It is a common trick among the witch doctors—of whom our friend yonder seems to be one—to divine events by means of the smoke from a fire built to the accompaniment of special incantations."

"Well, that's cheerful," commented Billy, "but tell us, Professor, how often do they hit it right?"

"Nine times out of ten, young man," said Professor Wiseman impressively fixing Billy with his gaze just as he would have impaled a bug or grasshopper, "and the tenth time they come so near the truth as to be uncomfortable."

"I have heard of such things, but I always put them down as impossibilities," gasped Frank.

"Just travelers' tales," said Billy.

"There are many things for the young to learn in Africa," remarked Professor Wiseman coldly and gazing at Billy with squashing intentness; "the young do not believe many things merely because they are young—and foolish."

"Gee! that was a nailer for fair," said Billy afterward. "I felt as if the Doc was running a big blue pin through me and sticking me on a bit of cork."

That morning, as the start for the interior was not to be made till the next day, M. Desplaines asked the boys if they would care to try a little fishing at the foot of the famous Jumbari Falls which lay on a branch of the Bari river a short distance from the town. Of course the boys assented eagerly, but as it was found that only Frank and Harry were expert canoeists, it was agreed that the others should fish from the bank while the two young leaders trolled their lines from a native built craft. This canoe was kept at the falls—to which they tramped the two miles overland by a narrow trail.

The falls were a magnificent sight. From a dark red rock, fully two hundred feet in height, a great volume of water poured its roaring current into a boiling pool below. The cliffs shot up sheer on all sides and were covered at the bottom with luxuriant green growth like seaweed, while higher up, ferns, as big as rose-bushes at home, and trees of a hundred varieties clung wherever they could find a root-hold. As the party arrived at the top of the ravine and gazed down, the uproar of the water was so terrific as to render any speech inaudible. M. Desplaines, who led the party, pointed to a hole in the rocks and a second later vanished into it.

At first, consternation seized on the boys who thought that an accident had happened, but seeing not hearing Professor Wiseman's reassuring laugh and noticing him plunge after M. Desplaines, the boys rightly concluded that the aperture was a subterranean entrance to the foot of the falls. And so it proved. A steep flight of steps was cut in a deep cleft of the cliff down to the water's edge. A few minutes after they had begun the descent, the little party stood on the brink of the whirling pool into which the mighty falls roared their thousands of tons of water. Following M. Desplaines, they advanced down the stream to a point where a bend shut off like a rock curtain the deafening uproar of the cascade. Here a canoe lay moored and Frank and Harry stepped into it and shoved off. Their lines and other equipment they had in their pockets.

As they shoved out M. Desplaines shouted something that they did not catch and pointed down the stream. How near the fact that they could not hear his words was to come to costing them their lives neither of the boys guessed.

CHAPTER V

THE POOL OF DEATH

"Say, Frank, have you noticed that we are going to have a hard paddle back against this current?"

The boys had been fishing about an hour when Harry spoke. So engrossed had they both been pulling in fish of a dozen strange varieties and brilliant hues that neither of the lads had noticed that the canoe had drifted down stream far from the starting point and that in fact when they looked up they were in an entirely strange part of the river.

"You are right, Harry," rejoined Frank, as he looked up at the steep banks on either side of them, "we have drifted a considerable distance. Come on, out with the paddles and we'll be getting back."

But it was one thing to talk of getting back and quite another thing to do it. The boys, after an hour of paddling, were dismayed to find that although their arms ached with the exertion and they were dripping with perspiration, they had made hardly any progress against the current.

"It's too much for us," gasped Frank.

"What on earth are we going to do?" asked Harry with blanched cheeks.

Frank glanced at the shore on either side. For a minute he had entertained a thought of landing and walking back along the beach. But there was no beach.

The river boiled along between narrow walls which shot sheer up from the water. There was not even a niche in their smooth surface to afford a foothold to a mountain goat. They were caught in a trap.

The only thing to do was to drift down the river and trust to luck to find a landing-place. In their extremity they shouted at the top of their voices to let their comrades know of their plight, but their cries were unanswered and they began to wish that they had saved their breath to use in the task of keeping the canoe steady in the current.

While they had been pondering their situation, moreover, they had been swept with almost incredible rapidity down the river. The walls here grew narrower and narrower and the water fairly boiled in its narrow confines. Its dark surface was flecked with white foam, and to make matters worse, as the walls closed in the light became fainter, till the boys were being carried downward through almost subterranean darkness.

In the intense gloom their white strained faces shone out like pallid beacon-lights.

"Hold her steady," said Frank in a tense voice as the canoe wobbled crazily in the swollen current.

"I'm doing the best I can," gasped out poor Harry desperately plying his paddle.

It the canoe was to get broadside onto the current, even for the fraction of a second, Frank well knew that nothing could save them. It was a terrible situation.

Helplessly they were being borne at dizzy speed to what seemed almost certain death—for certain it was that they could not hold out much longer. Already their overstrained muscles were only mechanically doing their duty, but before long Frank realized that even his-well-trained young body must collapse—and then, what?

Suddenly there was borne to their ears a sound that made both boys chill with terror.

It was a mighty roaring like the furious boiling of some giant kettle. A thousand shouting voices seemed blended into one to form the music, of this ominous orchestra. Louder the noise grew and louder, as the pass through which the river now tore like a runaway race-horse grew narrower and blacker.

What could the awful uproar mean?

They had not long to wait before the truth burst upon them. They were nearing, at what seemed express speed, a whirling, roaring mass of waters that shouted at them like some animal calling for its prey. The boys' cheeks blanched as they realized that nothing but a miracle could save them from being sucked into this watery abyss.

Desperately they plied their paddles but if they had been useless further up the stream they were doubly inefficient now. If they had stroked against the rushing current with feathers they could not have had less effect in checking the death rush of the canoe, which was tossed along on the racing tide like a chip of wood.

Suddenly the canoe was struck a terrific blow.

Before either boy could realize what had happened they were both struggling in the water. So dazed were they by the mishap that it was several minutes before they understood that they were clinging to the to the trunk of some huge tree. It was this trunk that had wrecked the canoe and thrown them overboard.

In reality, though, they were little better off now than they had been while the canoe was being whirled down the river. It looked as if they had been saved from one death only to face a worse. With all their might they clung side by side. Dripping wet, half-blinded and bruised by the battering they got as the trunk smashed from side to side of the narrow passage, the indomitable American pluck of the two lads yet held good in this extremity.

"Is it good-by, Frank?" Harry found strength to murmur.

"While there's life there's hope," came Frank's brave reply in his favorite axiom. "We'll live to fly the old Golden Eagle yet, let's hope."

There was no time for further talk, even had the boys been in any position to consider conversation. The trunk was rapidly nearing the whirlpool—and death.

Small wonder that brave as the boys were a despairing cry burst from their throats as they saw what seemed the end of their ride close upon them. It was as if they could feel the breath of the Pale Horseman already blowing chilly in their faces.

But suddenly a strange thing happened.

Both boys had closed their eyes and only moved their lips in prayer as they saw that inevitably in a few minutes they must be sucked into the maelstrom. Now, however, they opened them in amazement.

The swift rush of the log to which they clung like drowned rats had stopped.

It took them only a few seconds to take in what had occurred. The great log swinging one end toward the swirling current had jammed clear across the stream and for a time at any rate they were saved from immediate death. In their joy they clasped each other's hands warmly but their first rush of relief did not last long. As a matter of fact they were not any nearer safely than they had been a few minutes previous.

The log, it was true, was jammed across the stream, but the consequent backing up of the impetuous current caused it to rush across the boys' refuge in such volumes as to almost sweep them from their perches.

It was very evident that they could not hold put indefinitely in this position.

Their attention was attracted as they clung to their water-swept tree-trunk by a dark object whirling about in the boiling pool. It was swept dizzily round and round in ever decreasing circles toward the middle of the fatal vortex. Suddenly it shot downward out of sight, but as it did so Frank had seen something that kindled one ray of hope—though a feeble one. Before the canoe had taken the fatal downward plunge it had hesitated for a minute as though caught on something; and then the boy leader saw for the first time that in the center of the pool there was a rock, although the water that submerged it to the depth of an inch or so prevented its being seen at first glance.

Frank turned to Harry and told him of his discovery.

"If we are cast into the pool let us make up our minds to get to that rock. Keep your mind concentrated on it. Don't let the idea leave you for a second and perhaps—I say 'perhaps'—we can make it."

Harry shook his head despairingly.

"I can hardly keep my grip on this tree. I don't believe that I could possibly manage to swim even a few yards," he groaned.

"You must," said Frank sharply. "Don't give in now, Harry. Stick it out."

Then as a sudden thought struck him he continued.

"See here, it's no good our wasting our strength clinging to this trunk any longer. Sooner or later we shall be swept off and the longer we wait the less reserve strength we shall have. Let us leave go now and swim for it."

Whatever reply Harry might have tendered to this desperate proposal he was spared making, for at that moment a wave of more than ordinary force—caused by the backed-up water striking the log—struck him full in the face and before he knew it the boy had been washed from the tree trunk and was being carried like a straw down the stream.

As Harry felt himself being carried along there was only one thought in his mind. It was not of death. When death is right upon a man or a boy he rarely thinks of it, but casts about for the best means of saving himself. Nor does—as some imaginative writers have told us—a man's whole past life come before him at such moments. No—the instinct of self-preservation is strongest when a human being is in the direst need, and so it was that in Harry's mind one thought kept hammering away like the strokes of a tolling bell.

"Try-and-make-the-rock. Try-and-make-the-rock."

Frank's insistence had done this much. It had caused the boy to recollect the one hope of salvation that the desperate situation held out. As he was swept down the torrent Harry made no effort to swim. It would have been worse than useless and besides he needed to husband his strength for the final struggle he knew was upon him.

The next minute he felt a sickening swirling sensation and realized that he was in the whirlpool's death-grip at last.

Faster and faster the boy was hurried in ever decreasing circles. Dizzy, half-choked with water, blinded and almost exhausted Harry, with the tenacity of a bull dog, still clung tenaciously to the one idea:

"Try-and-make-the-rock. Try-and-make-the-rock."

Suddenly, he was flung against a hard substance. With outstretched fingers he clutched at the slimy surface as of what he realized was the end of his journey at last. The great stone was covered with slimy weed, however, and his grasping fingers refused to clutch at any friendly niche in its surface.

With a despairing cry the boy was being swept in to the terrible mouth of the pool when he felt himself seized and pulled up out of the grip of the torrent. He knew no more till he opened his eyes and found Frank by his side. Both boys were on the rock—sitting on it in two inches or more of water. Fortunately in that climate the water was not so chilly as to cause discomfort, but this was about the only crumb of satisfaction the situation held for them.

"Well done, old fellow," said Frank as Harry opened his eyes. "You had a narrow escape, though."

Harry could only look at his brother gratefully. How deep was his debt of gratitude to him both boys realized without their talking of it.

"How did you gain the rock, Frank?" asked Harry.

"When I saw you swept off the tree trunk I slipped off too," replied Frank, "and when I felt myself dragged into the pool I struck out for the rock. I confess, though, I didn't have much hope of reaching it till I was slammed into it with a blow that almost cracked my ribs and knocked all the wind out of me. I managed however to grab hold of a depression in the surface and maintain my grip on it. I had hardly dragged myself up when you were hurled against it. I thought I had lost you, for the water pulled like a draught-horse, but I managed to hold on to you and here we are."

"And a worse position we could not possibly be in," added Harry.

"Unless we were in there," retorted Frank pointing, not without a shudder, to the whirling open mouth of the pool which had sucked down the wreck of their canoe.

"What is it do you suppose?" asked Harry wonderingly.

"The mouth of a subterranean river I guess," replied Frank. "I have read of such things."

"But why didn't Desplaines warn us of our danger," said Harry bitterly, "if we ever get out of this I shall tell him my opinion of him pretty strongly. We might have been killed and we may yet."

"He did warn us," replied Frank calmly.

"He did?"

"Yes."

"I should like to know when?"

"When we shoved off."

"You mean when he shouted something we couldn't catch and pointed down the river?"

"That's it."

"I thought he meant there was better fishing down, here," snapped Harry indignantly, "what idiots we were."

"Yes; not to notice how we were drifting," rejoined Frank quietly, "it's no use to blame Mr. Desplaines for this pickle. We have only ourselves to be angry with. I don't suppose he ever thought that two boys would not notice how they were drifting in a ten mile current."

"The point is how are we ever going to get out of it?"

How indeed?

As the boys looked about they saw little to encourage them. The chasm in which they were beleaguered was not more than fifteen feet across, but on either side shot up walls of rock so steep and smooth that not even a fern could find root on their polished surfaces.

Where the whirlpool sank into the bowels of the earth the walls came together at an angle forming a sort of triangular prison. At the top of this trap the boys could see a strip of blue sky and the outlines of the graceful tops of some bulbous stemmed palms but nothing else. Once a vulture sailed across the strip and sighting the two boys came lower to investigate. The sight of the carrion bird made both of the boys shudder.

"Ugh, he scents a meal, he thinks we're dead already," cried Harry disgustedly.

The sound of his voice echoed gloomily among the rocks.

"We're dead already," came back in sepulchral tones.

"I shan't try to wake that echo up again," said Harry in a low tone and shivering at the uncanny voice of the rock.

Neither of the boys spoke for a long time. They sat there silently, occasionally standing up to get the stiffness out of their limbs till the strip of sky above began to darken to gray.

"Well, here goes!" exclaimed Harry suddenly.

Frank glanced sharply up. He did not like the wild tone in which the words were spoken.

"What is it?" he asked sharply.

"I'm tired of this, I'm going to swim for it," replied Harry with a foolish, hysterical laugh.

Frank saw what had happened. The boy had become half-delirious under the mental strain he had undergone.

"Sit down, old fellow," he said kindly, "help will come soon I am sure."

"Yes, a steamboat will come sailing down the river and take us home in the captain's cabin I suppose," said Harry foolishly.

But nevertheless Frank's stern command to "shut up" and not make a foot of himself brought him to his senses and he said no more till the stillness was broken by a sudden cry from above.

"Bosses—oh, bosses."

"Ahoy there; castaways!"

Frank looked up.

The cry of joy he gave set the echoes flying in the gloomy canyon.

It was the black face of Sikaso that was gazing down on them and beside it was Ben Stubbs' weather-beaten countenance. Behind them were Billy, Lathrop and the rest.

"Hold on there and we'll get you out of that in two shakes of a duck's tail," cheerily hailed the old adventurer. "We guessed you'd be here and we brought a rope as long as a man of war's cable with us. Lucky thing we did."

The next minute a long rope of vegetable fiber came snaking down the side of the cliff and to one end of it clung Ben Stubbs. As he reached the bottom—the rope being cautiously paid out from above by his companions—the old seaman swung himself outward from the face of the rock and "in a brace of shakes," as he would have said, stood alongside the two boys. In a second his sharp eye took in Harry's wild looks and hysterical greetings and realized what had happened.

"Now, Frank," he ordered, giving the young aviator the end of the rope—"catch hold tight and when you are ready give the word."

"But Harry—" gasped Frank, "I can't leave him. Let him go first."

"I'll bring him up. He can't look after himself in the shape he's in and you are too weak to attempt to help him. Now no talking back. I'm boss now. Up aloft with you. Haul away there!"

The next minute Frank, clinging to the rope, was being hauled cautiously up the side of the sheer cliff by careful hands and shortly he was in the arms of his friends.

Ben Stubbs—to whom the rope with a weight at the end of it had been swung pendulum wise—next appeared at the summit with Harry in his strong grip. But it was a white faced inanimate burden he carried. The boy had swooned.

"He'll be all right in a few minutes," said Ben Stubbs as M. Desplaines and the others all tried to explain at once to Frank how Sikaso had guessed what had happened when the boys did not return. The Krooman had led the party by secret native trails to the cliff top. Frank clasped the huge black's hand with real gratitude and tears of thankfulness brimmed in his eyes.

"How can I ever thank you," he said.

"Um—white boys keep away Pool of Death, Sikaso much pleased," replied the Krooman turning slowly away with a sad expression on his face.

"His own son was drowned in it several years ago," said M. Desplaines briefly.

CHAPTER VI

A SNAP-SHOT FIEND IN TROUBLE

The morning after the events recorded in the last chapter was one of these sparkling ones that are occasionally to be met with on the West African coast and was the forerunner of a day of great bustle and activity for the boys. With the vitality of healthy youth Harry had completely recovered and was indeed surprised to find himself feeling so good after what he had been through. Privately he inspected his hair in the mirror to see if it had turned white and was secretly much astonished to find it the same color as before.

"I wish mine would turn white or potato color or something," said Lathrop, to whom Harry confided his expectation, "this red thatch of mine is a nuisance. At school I was always Brick-top or Red-Head and out here the natives all look at my carrot-colored top-knot as if they'd like to scalp me and keep it for a fetish."

Both boys laughed heartily over Lathrop's half-assumed vexation. As a matter of fact he had been the butt of many jokes in school on account of his blazing red hair and in Africa the natives with their love for any gaudy color had already christened him Rwome Mogo or Red-Top. Of this, however, he was fortunately ignorant, as he might have been tempted to go out and dispatch half a dozen of them if he knew of their term for him.

Down at the river bank, cross the evil-smelling lagoon at the back of the town, Frank and Harry had their hands full directing shouting, laughing Kroomen how to load up the canoes. From the canopied steam launch that lay alongside the rickety wharf the black engineer—an American Negro—watched with great contempt their labors, which they enlivened with songs from time to time.

"Them's de mos' good fur nuffingest niggahs I ever did see," remarked Mr. Rastus Johnson—that was his name—with undisguised contempt.

Nevertheless by noon the canoes had all been leaded and the farewells to the kind M. Desplaines and his family said. After a swift final inspection Frank pronounced everything ship-shape and even Doctor Wiseman who had been fussing about as Billy said "like a hen with one chicken—and that a lame duck," over his tin cases and poisonous looking bottles, announced that he was ready to start. The twelve chattering Kroomen who were to go as far as the Bambara country with the expedition were seated two in each canoe. They were along simply as camp attendants and packers and would by no means go any further than the borders of the Bambara country which they said was the dwelling-place of "bery bad man sah."

Just as the little launch, flying the stars and stripes out of compliment to the boys, was drawing out into the stream with a long blast of her whistle, a tall, black form came racing along the bank and with one bound cleared the five feet or so between the launch and the shore. It was Sikaso.

"So you came after all," said Frank, turning to him, after a bend in the river had hidden the waving Mr. Desplaines from sight and they were settling down in the launch.

"Sikaso see in the smoke I come—I come. If I see in smoke I no come—I no come," remarked the Krooman.

"He's traveling light anyhow," remarked Billy.

Indeed the giant negro's only bit of baggage was a huge axe, the handle of which was dented and scarred as if by many combats. Billy was about to run his thumb along its edge when with a gesture the mighty negro waved him aside. Instead he took Billy's handkerchief from the young reporter's pocket and drew it gently along the axe blade.

It fell in two pieces on each side of his blade, severed by its razor-like edge.

"Sikaso is a good fellow to be friends with when he can make little ones out of big ones like that," remarked Billy, picking up the two fragments of his handkerchief, "that's a fine way to cut up a gentleman's wardrobe."

Bit by bit as the launch drove steadily up the muddy river—from whose jungle-grown banks arose a warm, moist vapor—Frank drew from the grim-faced old Krooman some of his history. He had been a mighty warrior in the old days, he said, and the weapon he carried was his war axe with which he had killed uncounted enemies. A rival tribe, however, had killed his father and mother and driven him to the coast with the few survivors of his village. Here he had shipped on an American trading brig for New York where he had picked up the knowledge of English he possessed. He also worshiped America as "free man's country." But Africa had called to him and some three years before he had returned on another ship and meant to die there, he said.

"Why did you wish to go with us?" asked Frank as the native concluded his story.

"It was written so in the smoke, white boss," replied the veteran simply. "The ju-ju in the smoke strong ju-ju. He knows many things."

"Is that the only reason you have for coming?"

"No, boss, I tell you truth," replied the old warrior, "some day I find the chief who kill my father and my mother and kill my friends." He glanced significantly at his axe.

"In the Moon Mountains maybe I find him—maybe not. But some day I shall and then—"

He said no more, but as Frank remarked to Harry when the former recounted his conversation to his brother later:

"I shouldn't much like to be that man when Sikaso meets him."

The launch and the small flotilla she towed forged steadily up the stream all that day and at nightfall drew alongside the bank at a spot where a clearing planted with bananas clearly indicated the presence thereabouts of a native village. As soon as the launch was moored to the bank the adventurers scrambled out—not sorry of a chance to stretch their legs—and looked about them wonderingly. They were really in equatorial Africa at last, and even as they looked there was a sound borne to their ears that brought home to them strongly how very far away they were from old New York. It was a pulsing, rhythmic beating something like a drum and yet unlike it. They looked questioningly at Sikaso.

"Tom-tom," said he briefly.

"Is it a friendly village, Sikaso?" inquired Doctor Wiseman.

"Friendly to some—not to all," replied the Krooman, who for some unaccountable reason had taken a strange dislike to the professor. "Come," he said, intoning to Frank and Harry, "we go see get chicken, maybe pork."

"Say, can't we come along, Frank?" asked Billy and Lathrop their faces falling.

Frank consulted Sikaso who merely said:

"Little fat white boy, with round, glass four-eyes talk too much."

"Well," laughed Frank, "I think I can promise for him that he won't do any talking that will cause any harm this evening."

"Talk too much, indeed," grumbled Billy highly offended, "why at home my folks were thinking of having a doctor treat me for bashfulness I'm so retiring in my disposition."

As soon as the laugh that this remark of the disgruntled reporter had caused had subsided—even old Sikaso giving a grim smile as he took in the purport of it—the little party set out down a native trail toward the village.

As the tom-tom beating increased in loudness as the village drew near, the boys' hearts began to beat a little faster. At last they were about to see a real African village—such as they had read about in Stanley's and Livingstone's books—and other less authentic volumes. They almost stumbled on the place as they suddenly emerged into a clearing. It was a strange sight that met their eyes.

Arranged in a circle were fifty huts that resembled nothing so much as a collection of old-fashioned straw covered beehives, enlarged to shelter human bees. All about them women and children were bustling; setting about getting the evening meal. Before one hut sat a woman, pounding something in a stone pestle—"like the drugstore men use at home,"—whispered Lathrop to Billy.

The arrival of the little band created a stir. The hideous old man, with a sort of straw-bonnet, who had been beating on the antelope skin drum called by Sikaso a "tom-tom" saw them and instantly picked up his instrument and waddled off with as much dignity as his age and a much distended stomach would allow him. The younger men, however, advanced boldly toward the party. Some of them carried, spears, others held Birmingham matchlocks of the kind the British and French Governments have in vain tried to keep out of the hands of the West African natives. These guns are smuggled in by hundreds, by Arab traders who exchange the "gas-pipe" weapons worth perhaps two dollars a-piece for priceless ivory, and even human flesh for the slave dhows.

"Seesanah (peace)," said Sikaso gravely, advancing in his turn.

"Seesanah," echoed the tribesmen, who evidently recognized Sikaso from their greetings. The boys stood grouped in the background—Billy Barnes and Lathrop even viewing with some alarm the advance of the savage-looking natives.

"Well, he seems to have fallen in with several members of his club," remarked the irrepressible Billy as old Sikaso and the natives talked away at a great rate.

"I'm going to get a picture of some of these niggers when they get through," he continued aside to Lathrop.

"What; you brought a camera?" asked the other boy.

"Sure thing," replied Billy, "and if their ugly mugs don't break the lens, I mean to get some good snaps."

He drew a small flat folding camera from his pocket as he spoke and got it ready for action.

"Do you think Frank would stand for it? It might make trouble you know," said Lathrop.

"Pshaw," retorted the cocksure Billy, "what trouble can it make? I wish I knew bow to say 'Look pleasant, please,' in Hottentot, or whatever language these fellows talk."

By this time old Sikaso's 'pow-wow' was over and he motioned Frank and Harry forward. After they had been introduced to the chiefs and headmen of the village, the "big chief," a villainous-looking old party with only one eye and his legs thrust into a red shirt—into the armholes that is, with the rest of the garment rolled round his waist—announced he was ready to give fresh provisions for calico, red and blue, and several sections of the brass rod that passes for currency on the West Coast. While Frank, Harry and Sikaso were bargaining behind a hut, over the price to be charged for a razor-backed porker of suspicious appearance the village suddenly became filled with an uproar of angry shouts and tumult.

"What can be the matter?" exclaimed Frank, as the boys, followed by the old chief and Sikaso, rushed from behind the hut to ascertain the cause of the disturbance.

Standing in the center of a crowd of excited villagers was Billy Barnes, his helmet knocked off and an arrow sticking through it. He looked scared to death as well he might, for by his side was a stalwart young African, brandishing a heavy-bladed spear above his head. At the young reporter's feet lay the ill-fated camera that had caused all the trouble.

What had happened was this. As soon as Frank and Harry and their companions had left him and Lathrop alone, Billy had started to carry out his determination to take some pictures. The first subject he selected was a serious-faced little baby, innocent of any clothing, that sat playing with a ragged dog at, the entrance of one of the beehive huts. He had just clicked the button and exclaimed:

"This will be a jim-dandy," when he felt something whistle through the air and the next minute his hat lay at his feet with an arrow in it. In an instant the child's father—convinced that Billy was putting Ju-ju medicine on the child—was upon him, armed with his big hunting spear and followed by half the village. Even Billy—scared as he was—did not realize how very near to death he actually came to being. Sikaso's shouted words in a native dialect caused the tribesmen to fall back but they still muttered angrily.

Stepping swiftly up to the camera Sikaso with a single blow of his axe smashed it to pieces.

"Here, that's no way to treat my camera!" Billy was indignantly beginning, when Frank gripped his shoulder in an iron-clutch and whispered:

"Shut up; if you don't want to make more trouble."

Billy was starting on an angry remonstrance when he caught Frank's eye. The young leader was really angry and Billy prudently refrained from saying any more.

As for Sikaso—after demolishing Billy's machine, he turned to the tribesmen and addressing them in stately tones said—as he afterward translated it to Frank:

"Village fools. You see there is no magic in the little black box. It is nothing but a child's plaything for the fat, spectacled idiot." (This part of the oration Frank did not communicate to Billy.) "You see I have smashed it. Do I fear? Do I look now like a man in terror of the white man's medicine. It is nothing. It is broken and gone like the cloud before the wind, like the shadow on the mountain side."

The effect of all this was soothing and the boys left the camp, to order some of their packmen to bring home the provisions, with light hearts. As for Billy his ears burned by the time Frank got through reading him a lecture.

"I'm sorry," he said bravely, "and I won't do it again. Gee! talk about 'press the button and we'll do the rest.'"

"They nearly did it—didn't they," laughed Frank, his good humor quite restored.

CHAPTER VII

A TRAITOR IN CAMP

It was a week later, and the launch having towed the expedition as far up the river as Frank decided was necessary—before they struck out into the unknown land of the cannibals, winged men, and the ivory hoard—had returned to civilization several days before, carrying with it letters from all the adventurers which they felt might be the last they would write for some time. The spot selected for the permanent camp was a sort of park-like space covered at its edges with masses of manioc and banana bushes. Beyond towered huge tropical trees and beyond these again the blue outlines of the distant Moon Mountains in which, according to old Barr's map, lay the ivory cache.

It had been a busy week. The Golden Eagle II had been re-erected and her own wireless and the field wireless apparatus put in order. As our readers who have followed this series are familiar with the manner of setting up the great Chester aeroplane and her fittings, it would be tedious to repeat the description of the process. Suffice it to say that thanks to the clever simplicity of the "knock-down" arrangement, by which the ship could be taken apart and set up again, the operation of equipping her for active work was a comparatively light one. The extra gasoline and supplies for the camp in general were stored in a separate tent removed from the circle in which the boys' tents and those of Ben Stubbs and Professor Wiseman were pitched.

There was, too, a newcomer in the camp—a Portuguese named Diego de Barros. He was not a particularly well-favored individual, but he bore the reputation of having great power over the natives and of being very friendly to the white traders who penetrated into the interior. Once or twice there had been ugly talk about his being in league with the Arab slave and ivory traders, but he had managed to clear his name and along the Ivory Coast enjoyed the reputation of being an honest, reliable man. He had joined the boys' camp a few days before and his manner of coming was this.

While everybody was busy getting things in shape there had come a loud hail from the quarters of the native helpers, just outside the white man's encampment, announcing that a canoe was coming up the river. All hands had hastened to the river bank to find de Barros just putting his foot ashore from the canoe in which two natives had paddled him from the coast. He had with him some bales of cotton goods and a few gewgaws of various kinds and was bound, so he said, on a trading expedition into the back country. Further down the river he had heard, he explained, that the boys were camped where he found them, and he had determined to pay them a visit. The brief stay that the boys had interpreted this as meaning, however, had extended itself into three days and still Diego showed no inclination to leave.

"If he doesn't move on soon I shall be compelled to ask him to go," said Frank in an annoyed tone to Harry. "I don't want to be inhospitable, but we can't afford to have strangers hanging round the camp, there is too much at stake."

Harry agreed with him and the two boys decided to tell the Portuguese that evening as tactfully as possible that they were on a private enterprise and could not accommodate strangers. This decision arrived at, Frank turned to the steel strong box that was never out of his sight and drew from it the precious map of the Moon Mountains. Seated at the little camp-table—(the conversation just related had taken place in the Boy Aviators' tent)—the two pored over the document for hours. With dividers, compass and parallel rulers Frank, who was a skilled navigator, laid out an aerial course that would bring them, he calculated, unerringly to the spot marked by a red cross where—so old Luther Barr declared—lay the ivory that was to save Mr. Beasley from financial ruin and disgrace.

Frank laid his finger on the spot and exclaimed enthusiastically:

"There it is, Harry, and we are not so far from it now. In a few days we shall know whether we are on a wild-goose chase or not."

"Why, no doubt has ever entered your head that the ivory is there?" questioned Harry.

"Well, old fellow, you know there are others interested in this ivory beside ourselves—Muley-Hassan for instance."

"You think he had got ahead of us?"

"I did not say I thought so, I only say that it is possible that he may have done so."

"How could he have got wind of our coming?"

"In Africa there is a sort of underground wire for news," replied Frank. "I have no doubt that hundreds of natives far in the interior are by this time apprised of our coming."

Harry looked alarmed.

"That's bad," he said.

"Well, it couldn't be helped: but we may have other enemies nearer at hand."

"What do you mean?"

"That I don't like the looks of that Portuguese fellow. If he got wind of what we are doing he would be likely to ruin the whole object of our expedition."

"That's so. We'll have to get rid of him."

"Well, we are going to, and if he won't go for gentle means we'll try rough ones."

"Hullo, what's that?" exclaimed Harry suddenly.

The flap at the end of the tent toward which both of their backs had been turned had been suddenly drawn aside and in one quick, backward glance Harry made out the smiling figure of de Barros standing in the doorway. It might have been fancy, but he thought for a minute that the Portuguese had a peculiarly villainous expression on his dark, handsome features.

"Ah, senors," he said, as Frank, with a quick movement swept the map off the table—but not before de Barros's quick eyes had spied it. Fearing to replace the precious chart in the strong box, while the Portuguese lingered, Frank tucked it into his pocket.

"Ah, senors, good afternoon," grinned the unwelcome visitor. "I have come to say 'adios.' I am going up the river to-night and may not see you again for a long time."

"I am sorry to have you leave," said Frank with a heartfelt wish that de Barros would hasten his departure.

"I knew you would be," smiled the Portuguese, "but it is the lot of man to meet and part. Adios, senors, I go to make ready."

He vanished as suddenly as he had come upon the scene.

"What do you make of that?" inquired Harry.

"I don't know what to think. I have an idea that he was listening to every word of our conversation just now and that he saw the map before I had time to sweep it off the table."

Harry looked vexed.

"That's tough luck," he said. "If he overheard even a part of our talk he must realize the object of our presence in Africa. And," he went on, "I don't know a man on the Dark Continent whom I would trust less than Diego de Barros, even the little we've seen of him."

"It can't be helped now," said Frank briefly; "come on, let's go and put the finishing touches on the good old Eagle."

They worked the rest of the afternoon putting the big aeroplane in shape for her flight to the Moon Mountains which it had been determined to make the next day. It was almost dusk when Harry, who was working over the engines, asked Frank for the reserve park-plug box.

"It's in one of the canoes. I'll go and get it," said Frank, and at once set off toward the river bank for that purpose. His path led through a thick grove of bamboos which hid him from the view of the camp after he had traversed a short distance. As he merged on the river bank, whistling softly to himself, the young leader suddenly felt himself pinioned by arms that seemed of enormous strength—though, as the attack had come from behind, he could not see the faces of his assailants. The next minute he was lying flat on his back, bound and helpless with a bit of greasy cloth shoved in his mouth for a gag.

"Keep still, senor, and you shall not be hurt;" said a quiet voice near at hand, and Frank saw bending above him the sallow features of the smiling Portuguese.

"I just have to trouble you for that map I saw you put in your pocket, that is all," went on his captor, while the two huge negroes who had made Frank prisoner stood to one side immovable as carved figures.

"It is lucky for me that you came down to the river bank," grinned the Portuguese as he ran his hand over Frank's clothes, to ascertain the hiding-place of the precious map of the ivory cache, "otherwise I should have had to delay my departure till to-night, and possibly have cut your throat while you slept."

Frank felt as if his heart would burst with rage and mortification as the greasy, smiling Portuguese deliberately drew out the priceless document and gazed at it in triumph. He laid it on the ground beside him while lie resumed his search for other clues.

"That ivory belongs to my master—Muley-Hassan—now," he sneered; "did you think for a minute that we would ever let you white fools get it back again."

It was well for the Portuguese that Frank's hands were not free then. Had they been the dark-skinned traitor would have had a fight on his hands in a few seconds. But suddenly events took a strange turn.

The two blacks uttered a sharp cry of warning as the bushes parted and a huge form dashed out, whirling about its head a glistening axe.

It was Sikaso!

The next minute would have been Diego's last but that his two followers lifted him to his feet and, picking him up like a child, ran for his canoe with him. With a few rapid strokes they were in midstream and paddling up the river with powerful strokes while Sikaso raged impotently on the shore.

"Oh for one of the white men's fire-tubes!" he sighed, and even as he spoke a sharp reminder of the efficiency of these same "fire-tubes" whizzed past his ear in the shape of a bullet from Diego's revolver.

In a few steps the old black was beside his young leader and with a couple of strokes of his keen blade had set him free.

"Quick, Sikaso; the canoes—we must pursue him. Call the boys and Ben while I cast off the canoes. Quick, we have not a minute to lose."

Although Diego in his hurry had not carried off the map but left it lying on the ground, still Frank realized that the Portuguese had not actually needed the document to aid Muley-Hassan to find the cache. The Arab was no doubt familiar with the location anyway, but to head off all danger of the boys getting there first, it was vital to stop Diego at all costs. In a few bounds Frank reached the little indentation in the bank where the canoes were kept.

As he gained it he fell back with a groan and, brave boy as he was, he leaned weakly against a tree for support as the true extent of the crushing disaster that had occurred was borne in on him.

The canoes were gone!

The cunning rascal, Diego, had devised his plan well.

The painters of all the craft had been cut, and by this time they were doubtless miles down the stream.

CHAPTER VIII

A BATTLE IN THE AIR

The consternation with which the news of the loss of the canoes was received by the young adventurers may be imagined. It meant that they were cut off from communication with the coast entirely unless some unforeseen circumstances arose. But in spite of the oppression that naturally affected them at the first news of their serious loss, Frank's confident manner had its effect in restoring some sort of hope. Like the born leader that he was, Frank, the minute he recovered from the first effects of his bitter dismay, set about cheering up the others.

"We've always got the Golden Eagle," he comforted, "and anyway it's likely if no one stops them, that some at least of the canoes will drift down the river to the coast. M. Desplaines will no doubt be able to surmise something serious has happened when he hears of their arrival and will send aid. In the meantime we have to consider what we are to do about the ivory cache."

As a matter of fact, as the boys learned later, none of the canoes ever reached the coast, being intercepted by river-tribes.

"I vote for going ahead," cried Harry, catching the optimistic note that his brother's words conveyed.

"That's the stuff," cried the young leader, "that is exactly what I was going to propose."

"How about you, red-top?" asked Billy turning to Lathrop.

"Of course I'm on," was the reply.

"I hate to dash your enthusiasm," said Frank, "but you fellows must see that it is impossible for all of us to go. My plan is to take Ben Stubbs along and leave you fellows and Sikaso here to guard the camp. Then, too, there is the possibility of a relief expedition arriving as soon as they discover that we have lost our canoes."

Old Sikaso leant apart on his mighty war-axe. He seemed to regret heartily that he had not had an opportunity of testing its metal on the head of the knavish Portuguese.

"What do you say to that plan, Sikaso?" asked Frank, who already placed a high value on the old warrior's judgment.

"That it is good, my white brother. Sikaso will stay with the four-eyed one and the ruddy-haired one and we will see that no harm comes to the camp of the young white warriors."

"It is well," replied Frank, who was falling into a trick of addressing the stately Krooman in the same grandiloquent fashion as the latter was in the habit of using, "I place my trust in you."

"Hum," snorted Billy, "four-eyes and red-top that's a nice combination for you! I'd like to do something to show that old chap that we can do just as much as anyone else when it comes to a show-down."

This remark, however, was made sotto voce to Lathrop, as Billy really stood in great awe of the six foot-two of ebony flesh and muscle that was Sikaso.

But Stubbs was delighted at his selection to accompany the boys in their aerial dash for the ivory cache. He spent half the night by lantern light pottering about the great craft and stocking her up with provisions and equipment for the journey. By the time he had finished it was almost midnight and he turned in to join the boys in the land of dreams where Frank and Harry, and doubtless the others, too, were already busy shooting down Diegos and hippopotami and flitting through the air above the great African forest and performing all sorts of wonderful feats.

At dawn everybody was up and about and after farewells had been said the Chester boys and their sturdy old companion clambered into the chassis of their craft. Frank had already laid out his course, which lay about two points west of north. The boy calculated that this direction would bring them within a few miles at any rate of the cache. To find it they would have to trust to persistence and a modicum of luck.

Old Sikaso, who had, of course, never seen anything even remotely resembling an aeroplane, stood apart from the excited group clustered about the big craft and gazed at it with astonishment, not unmixed with awe. The other Kroomen—the packers and camp-workers, however, gathered close about the machine and the boys had a lot of trouble keeping their busy fingers from unscrewing nuts and loosening turnbuckles.

"Anything more like a pack of monkeys on a picnic I never saw," exclaimed Billy as for the twentieth time he chased a long, skinny native away from the propellers, where he would have assuredly been decapitated if he had remained till the engine was started.

A few turns with the clutch thrown out showed the engine was running as true as on the day the Golden Eagle made her trial trip. The muffler was cut out and the effect of the wide-open exhaust on the Kroomen was magical. Within a second from the time that Harry threw in the switch and the gatling gun uproar of the exhaust made itself manifest, not a solitary one was to be seen. From the greenery of the jungle that rimmed the clearing, however, their frightened faces could be seen peering, like some strange sort of fruit among the tropical growth. Only old Sikaso stood his ground.

But even that stolid old warrior grasped his great war-axe a little tighter and stood erect as if about to face an unknown enemy as jets of blue flame and smoke shot from the detonating exhaust.

"All ready, Harry?" cried Frank to the younger boy who was at his old station by the engines.

"Ay, ay!" came the response in a hearty tone. "Then let her go."

With a quick movement Frank threw in the clutch.

The mighty propellers began to beat the air with the whirring sound of a swarm of gigantic locusts in full flight, and after a short run the great aeroplane took the air in a long graceful rising arc. Half an hour later, to the watchers in the camp, she was little more than a speck against the sky.

Frank, his eye constantly on the compass, kept the ship on a true course for the Moon Mountains which, now that they were flying far above the dense forest region, lay a rugged mass of blue and brown, piled like some giant's playthings—on the northwestern horizon.

Even from the distance at which the boys viewed them they conveyed an almost sinister impression in their rugged shapes. Their harsh outlines cut the sky in a serrated line like the teeth of a huge saw.

"Look, look, Frank!" shouted Harry suddenly as they were passing high over a small clearing.

Both Frank and Ben peered over the side in answer to the boy's excited hail.

Far below them was a strange sight.

In the center of the clearing were four huge African elephants solemnly conducting a sort of Brobdingnaggian game of tag. One of the great beasts would tap the other with its trunk and then would scamper away till it in turn was "tapped" by a blow that would have swept a small regiment off its feet.

Frank pushed over a lever and swung the ship in a circle so that they might watch the great animals to better advantage. Suddenly the boys saw one of the elephants, evidently seized by sudden rage, start goring one of its companions with its huge tusks. The attacked animal had no chance, and but for the boys would speedily have been killed.

"I'm going to give that big bully a shot," exclaimed Harry, and he got out one of the heavy rifles from the rack under the starboard transom.

"Wait, I'll drop a bit," said Frank.

In response to his manipulation the aeroplane dropped till she hovered not more than two hundred feet above the great animals. Then a strange thing happened. The shadow of the craft fell upon the center of the clearing in front of the dueling beasts and the on-looking pachyderms, and as it did so the bully stopped goring its mate and gave a snort of astonishment.

Its note of surprise quickly changed to a loud trumpet of terror as the great pachyderm saw swooping above it what must have appeared to it an aerial inhabitant even larger than itself. Its note of fright was echoed in a chorus that sounded like an assemblage of cracked trumpets as the others also sensed the impending danger.

"Now let him have it," shouted Frank.

Harry's rifle cracked and the big bully staggered. Twice more the boy fired and the huge creature staggered on to its knees and then with a mighty groan rolled over on its side. The others, even the wounded one, had made off as soon as they had caught sight of the hovering Golden Eagle.

Even from the height at which they were the boys could see that the dead animal had an enormous pair of tusks, no doubt extremely valuable.

"We ought to have them there figure-heads," commented Ben Stubbs. "What do you say if we drop down and get them?"

Frank looked at his watch. It was half-past nine.

"We cannot be more than a hundred miles now from the foot of the range," he said, "and I suppose we have plenty of time. We might as well drop and get them as let some native tribe have the find and then get skinned out of them by an Arab trader."

As he spoke the boy set the planes for descending and the Golden Eagle settled down—after a few minutes rapid falling—fairly in the center of the clearing. It was almost a fairylike spot. On every side it was hedged in by the densest jungle vegetation, the solid walls being broken here and there by elephant paths leading off into the green tangle.

The little glade in which the Golden Eagle had settled was covered with short, yellow grass and had been trampled almost bare of vegetation, apparently by the gambols of countless generations of elephants.

"This must be one of the elephant playgrounds I have read about," exclaimed Harry, looking about him.

"No doubt it is," replied Frank. "But look at those tusks, why there's ivory enough there alone to give us all a nice wad of pocket money."

Ben Stubbs, with one of the small axes, at once set about hacking out the dead elephant's huge tusks and a long job it was. Finally, however, he managed to cut them free and clear and the boys loaded them into the aeroplane.

"Now we are all ready for a fresh start," said Frank as they clambered in after him and settled down in their places; but a startling interruption occurred.

With a wild yell, that struck a sudden chill to the heart of every one of the little group, a band of beings that at first sight looked like nothing so much as huge gorillas, burst from the forest on every side.

Their heads were misshapen and flat and their protruding lips were daubed with white and red clay which gave them a ghastly unearthly look. From their ears hung huge ivory pendants. They carried elephant skin shields and were armed with spears and bow and arrows. As if they did not consider themselves sufficiently hideous, several of the tribe had cut their faces in long stripes and the hardly healed scars of these wounds rendered their already sinister faces terrifying indeed.

Desperately Harry threw over the wheel and the engines started faithfully to respond but not before half a dozen of the savages had thrown themselves on to the aeroplane.

Their weight held her down although she scudded over the ground; and in the meantime the other natives started pouring a shower of arrows and spears into her. Fortunately none of these struck the boys although Frank felt an arrow whiz through the loose sleeve of his shirt.

"Get those fellows off or I can't get the ship up," he yelled.

Harry and Ben Stubbs fired their automatics into the clinging mass of savages.

Two dropped and the aeroplane began to rise but the others desperately clung on.

"Get 'em off," shouted Frank, as he desperately strove to raise the air-craft.

As he spoke he fell back with a cry of pain.

An arrow had struck him on the shoulder inflicting a painful wound.

Like a flash Harry took in the situation and leaped to the steering wheel. As he did so the savage with whom he had been contending clambered clear into the chassis. At the same instant Ben Stubbs' revolver dispatched the last of the men clinging to the planes and the Golden Eagle began to rise.

As she shot upward the savage who had climbed into the chassis gave a wild shriek of real terror. But his outburst didn't come before he had made a savage lunge at Ben Stubbs with a short heavy knife. The solo adventurer dived under the black's arm and struck it upward as he lunged and the weapon went whirling groundward out of the air-ship.

With a cry of despair the savage rushed to the edge of the car and was about to throw himself into empty air when Ben leaped forward to try to restrain him.

But it was too late.

As the boys' sturdy companion gallantly attempted to save the savage's life a flight of arrows whizzed up from below.

With a groan the man on the edge of the car pitched forward into open space, pierced to the heart with an arrow sped by one of his own tribesmen. Down he shot like a stone to the earth below, while the Golden Eagle—as if rejoicing in her escape, shot upward and onward.

CHAPTER IX

THE VOICE OF THE MOUNTAIN

Frank's wound fortunately turned out to be nothing very serious—though painful enough—and after it had been treated with antiseptics from the medicine chest he declared that, aside from the stiffness and soreness, he felt no ill effect.

"Those fellows certainly gave us a sample of what we may expect," remarked Harry, examining the hole in his shirt where the arrow had ripped through.

"It was quite as narrow an escape as I care to experience," agreed Frank. "How about you, Ben?"

"Wall," said the old adventurer, "I don't know as how I think that kind of excitement is as beneficial fer the health as the rest cure."

Meanwhile the Golden Eagle, plowing through the clear African air at fifty miles an hour, rapidly drew nearer and nearer to the mysterious Moon Mountains.

As they neared the range the extraordinary character of it was revealed more and more clearly. Seamed with deep gloomy abysses and almost bare of vegetation, except a few scanty groves of palms and the hardier tropical trees, they seemed indeed fitted to be the theater of dark mysteries and the haunt of savage tribes.

"Well," exclaimed Harry, as he scrutinized the strange mountain mass through the glasses, "I should say that if those Winged Men are to be found anywhere, here is where they'd reside."

"I should think they'd use their wings to get out—a nastier looking lot of mountains I never saw," was Ben's reply.

Frank made no comment, but the sinister character of the mountains they were so rapidly approaching impressed itself on his mind nevertheless. Eagerly he scanned the range for the first sign of "The Upturned Face." Harry and Ben, too, gave quite as eager scrutiny toward the discovery of this striking mark of the ivory's hiding-place.

All at once it shot into view with a suddenness that made the boys' beads swim.

It was as clear as daylight. The line of the mountain for which Frank had the Golden Eagle II now directly headed was unmistakably the outline also of a hawk-nosed facet.

If the mountains themselves had an evil, menacing look, the stone face possessed this same quality in an infinitely greater degree.

"Well, if we've got to go looking for ivory right under that face the sooner we find it the better," exclaimed Ben. "I'd hate to be shipmates with the fellow who sat for that portrait."

"No human being ever sat for it, Ben," laughed Frank; "it's a mere freak of nature which has so disposed the mountain mass at this point as to give the semblance of what the map-maker terms The Upturned Face."

"Well, if I had a mug like that I'd turn it down instead of up before some one did it for me," was Ben's comment.

The Golden Eagle landed on a plateau about halfway up the mountain, beneath the upturned face. It made an almost ideal camping-place, considering the rugged nature of their surroundings. In one part of it a small grove of bananas and palms had taken root, and their smiling greenery offered a refreshing contrast to the dark oppressive gloom of the giant rock masses piled all about. From the center of this oasis in the rocky range bubbled a tiny spring of water as clear and cold as if it had been filtered and iced. Frank's first act was to send out a wireless to the River Camp, telling of their arrival.

"Well, thank goodness, we've got something green and pleasant to look at," remarked Ben, as they set about transforming the chassis of the Golden Eagle into a comfortable tent by means of running up the canvas curtains on the aluminum frames provided for that purpose. Thus equipped, the chassis served the uses of an improved tent, as the floor was well above the ground and out of all danger of the unwholesome, vapors rising from the ground and also the scorpions and other reptiles.

But if the oasis itself was a pretty spot, it was made doubly so by the contrast it afforded to the scenery surrounding it. On all sides shot up frowning walls of rugged black rock which seemed to have been torn and ripped in some remote period by a terrific convulsion of nature. In places, too, the rock masses seemed to have been seared by subterranean fires. Frank gazed upward at the terrific character of the scenery about them.

"We shall need the rope-ladder," he announced suddenly after a long silence.

"The rope-ladder?" inquired Harry, "what for?"

Frank laughed.

"I mean the rope-ladder we use in the Golden Eagle. As you know, the only way to locate the cache is to strike a direct line down from the nose of the upturned face. That will bring us to the small cairn or pile of rocks that marks the Arab's hiding-place."

"He could hardly have chosen a better," remarked Harry. "Who would ever guess, unless they had the key to the mystery, that these mountains held such a fortune in tusks."

The rest of that day was spent in overhauling the outfit which they would need to use on their expedition of the morrow. Luckily the boots they wore had been fitted with "hob-nails" so that they were ideal for the tough climb that they had ahead of them. Each member of the three was to carry a pick and of course they all were to be armed, carrying several rounds of ammunition each in their cartridge-belts.

That night after a supper of fried ham, canned corn and pancakes—all cooked by the skilful Ben over a fire of wood collected from the little grove—Frank sent out a wireless to the members of the camp on the river bank and felt much reassured when Lathrop's "All well—good luck," came back through the air. It was delightfully cool on the mountain-side after the oppressive fetid air of the river and its neighborhood, and as Ben had remarked before they turned in:

"Fine weather for sleeping."

But sleep would not come to Frank. He tossed and turned on his transom bed and several times gazed out into the night through the canvas curtains. An unaccountable feeling of unrest possessed him. Could they get the ivory out of the cache before Muley-Hassan and his band arrived by land?

Fast as they had traveled through the air Frank realized that the Arab, who doubtless by this time had been informed by the treacherous Diego of the boys' bold dash, would push on at furious speed in order to head them off. That he would come accompanied by a well-armed band Frank could not doubt. He and Harry and Ben could only put up a feeble resistance against such an attack. There was only one chance to secure the ivory and that was to get at it before the Arab arrived. It all depended then on how quickly they could find the cache. Frank lit the lantern and shielding it so that it would not strike in the eyes of his sleeping brother, drew out the map and scanned it attentively.

Yes, here were the directions written in the queer hand of Muley-Hassan's follower.

"A line from the nose straight down to the cairn of stones."

It seemed simple enough and certainly the nose of the Upturned Face was as clearly to be made out as a ship at sea. But Frank had been too long trained in the hard school of adventure to underestimate the difficulties of any piece of work. They faced a hard job and none realized the fact better than the young leader.

At last he blew the lantern out and once more composed himself to sleep. He was just dozing off when a sufficiently startling interruption occurred. One which drove all further thoughts of rest from his head.

It was an extraordinary sound that brought the boy out of his bed with a bound and caused him to clutch his revolver with a heart that beat loud and thick in spite of himself.

Clutching his weapon the boy rushed to the door of the chassis tent and gazed out.

There was a bright moon which threw into inky blackness the depressions of the rugged mountains and threw up their projections into a blue glare. It was almost as light as day under that wonderful African moon. Had there been any one near the boy must have been able to see them.

But look as he would there was not a soul in sight. All about him stretched the barren frowning mountains sleeping under the moon.

But the sound that he had heard?

There was no mistaking it. It had been too like the low humming of a human voice for him to have been misled. Perhaps he had been dreaming?

But as if to give the lie to any such supposition the strange sound that had so alarmed him at that moment made itself manifest once more:

"A-hooo-A-AH-HOOO-00-a-ho-ho-ho-o-!"

It started softly and gradually ran up the scale till it reached a crescendo shout and then died out in a soft sound like a woman's wail. Heard anywhere the sound would have been alarming enough, but coming as it did in the midst of these unknown, mysterious Mountains of the Moon it struck a chill to the boy's heart and caused his scalp to tighten in a manner that even the bravest man or boy in the world would have had no reason to feel shame over.

A human enemy, a foe he could see, Frank would have faced with iron nerve; but this strange wailing noise coming from what quarter of the compass he could not judge—was so uncanny that he was really disturbed. He bounded into the chassis and roused Ben and Harry. He had hardly whispered to them the extraordinary intelligence when again the voice arose.

"A-ho-ho-h-o-o-o-A-h-hoo-ho-AH-HO-HO-O-O-O-AH-ho-h-o-o-o-o-o-o!"

"Well, who?" roared Ben angrily, "come out and show yourself, you human hyena, and I'll put so much lead in your system you'll be worth a nickel a pound. Come, you old Ah-Hoo, and I'll show you who I am quick enough—shiver my topsails!"

But the only reply to Ben's tirade was the dismal echo of his voice among the rocky chasms.

"Shiver my topsails!" roared the echo and then the hills bandied the cry about from ridge to ridge till it died out in a whisper:

"My topsails!"

"Hum," remarked Ben, "I don't think I'll talk so loud around here. There seem to be a lot of folks listening. Such a dreary hole as this I never—"

"Never," sighed the echoes, "—never."

"Here, I can't stand this," cried Harry. "I'm going to send a bullet up there the next time that fellow starts 'Ah-hooing."'

But as the strange mournful cry rang out once more the boys paused in bewilderment.

There was no locating the sound.

It seemed to fill the air. To come from every quarter of the compass at once.

CHAPTER X

THE ARAB'S CACHE

The mysterious cries were not repeated that night although the boys laid awake till daylight listening for any repetition. No theory they could advance, although these ranged all the way from cannibals and gorillas to ghosts, had any effect on the solution of the mystery. They finally agreed to trust to solving it in some chance way, and like sensible boys did not continue to worry themselves over the unsolvable.

Frank's first action was to send out a wireless to the river camp and to his great relief he found that events there were still proceeding with the same regularity as before. Nothing had occurred to mar the even life of the young adventurers left behind. This was the tenor of the message, but there was something about it that worried Frank. Lathrop, he knew, was an expert wireless operator, but the sending that he performed that morning was so jerky and irregular that the rankest amateur might have done better.

"What is the matter?" asked Frank sharply after the sending had become even more unskilled and shaky.

There was no answer; which caused Frank a vague feeling of apprehension. He speedily drove this impression from his mind, however, with:

"Pshaw! the sleepless night I passed has made me nervous."

After breakfast there was so much to be done that there was no more time to waste on gloomy forebodings and the boys started, as soon as the camp had been put in order, on their expedition up the mountain-side to the Upturned Face—which was to be the starting point for the uncovering of the secret ivory hoard.

The climb was quite as stiff as Frank had anticipated and, laden as they were with the rope-ladder and the other equipment, it was rendered even tougher. All three carried water-canteens covered with wet felt, containing half-a-gallon each. Frank had insisted on this as it was doubtful if they could find water at the summit of the mountain.

As the sun rose higher in the sky and beat down on the bare rock ridges over which the adventurers were making their way, it became as uncomfortable as any expedition on which the boys had ever beer engaged.

"Talk about New Mexico or Death Valley," exclaimed Harry, "I feel like a piece of butter rolled up in a paper and I've melted."

"I feel like a Welsh rarebit myself," laughed Frank, "how about you, Ben?"

"I feel like a pot of boiling tar with a fire lighted under me," growled the veteran angrily; "consarn these rocks, I'd give a whole lot for a bit of that shade we left behind us."

Despite the discomfort and the heat, however, they struggled on up the mountain-side, frequently using the rope-ladder to get over rough places, and at about noon they stood beneath the steep rock cliff that formed the nose of the upturned face.

It was easy enough then to reach a spot below the tip and Frank, with a long cord he had brought for the purpose, laid out a straight line from the point down the southern slope of the mountain-side. While they were busy about this they were startled by a repetition of the same strange cry, half-warning, half-savage, that they had been so alarmed by the night before.

"A-ho-o-o-o-AH-H-O-O-O-a-h-o-o-hoo-o-o-o-o!"

"Great Scott," yelled Harry, "what on earth do you think of that?"

Frank—considerably startled himself—had, however, made a determined effort to ascertain the source of the sound as it rose and fell in its strange cadence.

"I've got it!" he shouted; now with a cry of triumph.

"Got what?" cried Harry, as if he feared his brother had suddenly become infected with some strange complaint—"rabies or the pip?"

"The noise—I mean I know where it comes from," cried the excited boy.

"Where?" chorused Ben and Harry.

"From somewhere about the Upturned Face," cried Frank triumphantly, "Hark!"

The strange wailing cry rang out once more. They all listened intently.

Sure enough it seemed to proceed from the sinister countenance carved in the living rock above them.

"Well, here's where we end this mystery for all time," shouted Frank, drawing his revolver, "who is game to follow me?"

Of course Harry and Ben rushed to his side, and while the echo of the mysterious cry was still sobbing and sighing among the crags they dashed back up the mountain-side utterly oblivious now to the heat or anything but their determination to discover who or what had uttered the extraordinary cry. The side of the nose—or the nostril so to speak—was formed of a wall of rock fully twelve feet in height.

"You fellows give me a boost up there and I'll travel right along the face till I find out where the racket comes from."

On Ben's strong shoulders Frank was soon hoisted up to a height where he could lay hold of a projecting bit of rock and shin himself up on to the top of the nose.

"Look out he doesn't think you are a fly and try to brush you off," laughed Harry from below.

"No danger of that," shouted back Frank, "unless I lit on him in the Golden Eagle."

The surface of the face was as remarkable as its profile.

Apparently some forgotten tribe had at some time or other been struck by the facial outline of the rocks and had cut into the flat surface, which was upturned to the sky, eyes and a mouth, the latter well provided with teeth, in each of which was drilled a tiny triangular hole.

While Frank was puzzling over the meaning of these apertures there came a repetition of the weird cry, but this time the lad was so startled that he almost lost his balance and fell backward.

The call seemed to proceed from his very feet. Then, all at once, he realized what it was.

The strange sounds proceeded from the mouth of the stone face.

Frank ran to the edge of the steep declivity that formed the nose.

"Say, Harry, and you too, Ben, examine the surface below there very carefully for any holes. They will probably be small ones and in a row."

"None this side," announced the searchers after a lengthy quest.

"Try the other," ordered Frank.

They did so and after a few minutes of careful scrutiny Harry shouted that they had found a row of small holes pierced in the rock just below where Frank stood.

"Then we have solved the mystery of the voice," exclaimed Frank.

"What do you mean?" demanded Harry.

"That it is nothing more or less than an arrangement of holes through which, when the wind blows in a stiff puff, air is forced with violence enough to cause the cry that disturbed us so much last night," was the reply.

This indeed was the solution, and had the boys known it there are many such rocks in Africa, carved out by some forgotten race, and the weird cries that the vent-holes give out in the wind doubtless acted as a powerful "fetish" to keep away troublesome enemies.

"No wonder the niggers down below don't come near the Moon Mountains," said Harry, as they all buckled over the simple explanation of the phenomenon that had caused them so much alarm. "I wouldn't care to, myself, unless I knew just what made that cry."

"It certainly was as depressing as anything I ever heard," said Frank, "and now having solved the great mystery—let's get back to work."

The three adventurers went at the job with a will. The line was about a hundred feet long and the method of procedure was this: Frank tested the straightness of the line, as accurately as possible with his eye, while Ben and Harry carried it stretched between them. The end of each hundred feet was signalized by a stone, and Harry, who was at the end of the line, carried his end to this mark before they laid out a fresh hundred feet. In this way they must have measured off very nearly half-a-mile of the mountain-side when Frank gave a sudden sharp cry and pointed to a depression in the dark range immediately below them. As the others looked they echoed his cry and gave a dash forward.

Directly beneath them, about in the center of the little dip, was a cairn of rough stones perhaps four feet in height. In a few bounds they had reached the pile, which they knew meant the discovery of the ivory cache and the end of the most difficult part of their expedition. Little did they imagine the amazing things that were yet to happen to them and of which they were but on the threshold.

"Good Lord, look at that, boys!" exclaimed Frank, as they stood at the foot of the cairn.

There was a good reason for the boy's exclamation.

Distributed around the base of the pile were a dozen or, more human skulls.

"Are they those of white men?" asked Harry in an awed tone. Frank shook his head.

"No, they are those of negroes I believe," he replied after a careful examination, "and I imagine that Muley-Hassan killed them after they erected the cache so that they would not be able to spread the knowledge of its whereabouts to any of the marauding tribes who might even brave the ghostly voice when such a great treasure of ivory tempted."

A shout from Ben, who had been walking round the pile examining it from every view-point interrupted them. They looked up and saw the old adventurer pointing to the mountain summit where it cut the sky. Outlined against the deep azure was the object that had caused his exclamation. It was the figure of a man that had apparently been watching them intently.

But as they gazed the strange, crouched form suddenly vanished.

CHAPTER XI

THE AGE OF SIKASO

It was late afternoon of the day that Frank, Harry and Ben had left the River Camp. Lathrop, Billy, Barnes and old Sikaso had wandered into the jungle with their rifles, intent on bringing down some sort of game to replenish the camp larder. For hours they tramped about in the thick jungle and a fair measure of success had fallen to their rifles. Shortly before sundown the trio met in a glade not more than a mile from the camp and compared notes. To Billy's gun had fallen a plump young deer and Lathrop had brought down, not without a feeling of considerable pride, a species of wild hog which Sikaso proclaimed with a grunt was "heap good."

Flushed with triumph and carrying their own bag, the young hunters set out for the camp, arriving there at dusk. As has been told, it was not long after that that Frank's wireless from the Moon Mountains winged its way through the air and Lathrop was able to flash back in response an "all-well" message. The boys turned in early, Billy and Lathrop to their tent and old Sikaso to the rough shelter he had contrived for himself and which he declared was far more comfortable than any tent. Like a wild beast the savage old warrior disliked to have anything approaching a roof over him. It appeared to savor too much of a trap of some kind.

Billy might have been asleep five hours or so and it was approaching midnight when he heard a noise outside the tent door and a second later old Sikaso announced his presence by a whispered:

"Awake, Four-eyes, there is danger."

"What do you mean, Sikaso," demanded the half asleep reporter, "danger to our friends?"

"No; to us, and here and soon," was the disquieting response, "arouse your friend. We have no time to lose."

Billy was wide awake now and made a motion as if he would light the lantern.

Sikaso stopped him with a quick gesture.

"Do not light the lamp, my white brother," he whispered in the same tense tones, "to do so would be to reveal to those who are now approaching that we are awake and expect them. Rather let us pretend that we are unaware that they come and spring upon them like the leopard when she is least expected."

"Yes, but—" exclaimed Billy in a bewildered tone, "what do you mean, Sikaso, what enemies are coming? How do you know that they are approaching?"

"I have seen it in the smoke," was the somber reply; "the smoke never lies. After I lay down on my skins I could not sleep, I felt there was danger approaching us. From where I knew not. So I made the "fetish" fire. In it I saw a band of men coming toward us down the river and at the head of them was a dark man—a man you know well, my white brother with the four eyes."

"Diego!" exclaimed Billy divining the other's thought.

"Yes, Diego; cursed be the day that my war-axe did not cleave his ugly skull; but beside Diego there is another. Hearken to the words of Sikaso, the elephant in his rage is not more merciless, the serpent not more cunning, the crocodile not more savage in onslaught than this other. He is Muley-Hassan, the Arab, and the deeds he has done, my brother, when recounted turn strong men's blood to water."

Small wonder that Billy, as he hastily roused Lathrop, felt a shudder run through him. He had heard enough from Frank of the ways of Muley-Hassan to know that they could not well fall into the hands of a more pitiless foe and that now, with the Golden Eagle gone and the Boy Aviators already at the ivory cache, it was probable that the slave-dealer's rage would render him even more savage than was his wont.

In a few rapidly whispered words Billy apprised Lathrop of the situation. Like Billy, the other boy had no lack of pluck but his heart sank, as had his companion's, as he sensed the full meaning of Sikaso's warning.

"But perhaps the smoke was mistaken," he said eagerly, willing to grasp even at that straw of hope; but the old warrior's answer dashed his aspirations to the ground.

"The smoke is never mistaken," he said simply; but with such calm conviction that the boys, despite themselves, realized that the old Krooman had really the knowledge of grave peril approaching.

"Had we not better arm the other Kroomen?" asked Billy anxiously.

"It would be useless," was Sikaso's reply, "they are cowards. At the first sight of blood they would run to the forest like the sons of weaklings that they are."

"We must rouse Professor Wiseman at once," cried Billy.

"It is well," muttered Sikaso, "we shall need every man who can hold a rifle to-night but the professor is old, my brothers, and his heart is as a woman's."

"Well, he'll have to fight," said Billy with bloodthirsty determination. "I for one am not going to stand calmly by and have my throat cut, or worse still be taken prisoner by this old Muley-Hassan."

Old Sikaso glanced approvingly at him.

"Well spoken, Four-eyes," said he; "spoken like a son of a warrior."

Billy's ears tingled at the compliment, which was really in the old African's opinion the highest that could be paid to a man or a boy, and hurried off to wake "the bugologist" as be disrespectfully termed the professor. To his surprise, for he more than half expected an outbreak, Professor Wiseman did not appear particularly concerned at the news that Diego, and Muley-Hassan were—as the boys had every reason to believe—at that moment advancing on the camp.

"I will dress myself with all alacrity," he said, "and join you in your tent, but I must say I don't believe in all this witchcraft."

"Will this Muley-Hassan be well armed?" asked Billy, in a voice which was rather shaky, of their black friend.

"Plenty rifles," was Sikaso's brief reply.

"Don't you want a rifle or at least a heavy caliber shotgun?" asked Billy.

The old warrior laughed and swung his mighty axe round his head till the blade flashed like a continuous band of steel and the air whistled at the cleavage of the sharp edge. Then he began to sing softly a war-song which may be roughly rendered in English thus:

"At dawn I went out with my axe into the red fight;
Like the grass before the fire, like the clouds before the wind,
I drove them. I, Sikaso, I drove them.
There were rivers that day; but the rivers were red.
They were the rivers of the blood of my enemies;
With my war-axe I killed them.
This is the song of mighty Sikaso, and his terrible axe of death."

Although the boys of course did not understand the words, the fierce voice in which the old warrior intoned the chant made them realize what a terrible foe he was likely to prove in battle. But now as Sikaso brought his song to a conclusion and rested his axe on the ground, leaning on its hilt, he suddenly stiffened into an attitude of close attention.

"Hark, my white brothers!" he cried, "the war-eagles are gathering for the slaughter."

But the slight sound the keen ears of the savage had caught without difficulty was longer in making itself manifest to the two white boys. After a few minutes of listening, so intense as to be painful, they likewise, however, distinctly heard the regular, rhythmic dip of paddles coming down the river.

"There are six war canoes full of them," announced, Sikaso, with almost a groan, after he had given close attention to the sounds. "Alas, my white brothers, there is little use of our giving battle."

"Well, I for one am not going to give up without dropping a few of the cowardly wretches," cried Billy.

"Nor I," echoed Lathrop, enthused by Billy's brave example.

The old warrior's eyes kindled as he gazed at the two brave young Americans, each clutching his rifle and waiting for the moment to arrive when they could use them.

"If we only had had time to throw up a stockade, my brothers, we might have driven them off yet," he cried.

"Well, we'll give as good an account of ourselves as possible," declared Lathrop.

And now began what has been acknowledged to be the most trying part of any engagement, from a duel to a battle—the waiting for hostilities to begin. It seemed that an interminable time had elapsed from the moment that they heard the first "dip-dip" of the paddles to the sharp crack of a twig sounded in the jungle directly ahead of them. The snapped branch told them that the enemy's outposts were reconnoitering to see that the camp was actually, as it seemed to be, wrapped in sleep.

Apparently the scout, whoever he was, was soon convinced of the fact that the adventurers were slumbering, for he advanced boldly from the dark sheltering shadows of the jungle and emerged into the bright moonlight which flooded the clearing in which the camp stood.

Billy raised his rifle to his shoulder and the next minute would have been the savage scout's last had not old Sikaso sternly seized and lowered the weapon, saying in a tense whisper:

"The time is not yet ripe, my brother. To fire now would be unnecessarily to give the alarm. Wait until they are massed thick and then fire into the bodies of the Arab dogs."

The scout didn't waste much time in reconnoitering. After a short time spent in peering about he dived once more into the forest and Billy whispered to Lathrop:

"Now it's coming, old man."

And come it did.

Five minutes after the scout had dived back into the forest a dozen dark forms crept from the bush and stealthily advanced toward the tent.

The leader had reached the door and Billy was frantically imploring old Sikaso to let him shoot when an appalling shriek rent the air.

The old Krooman's axe flashed once in the moonlight and the leader of the attacking party lay dead at the tent door, severed almost to the chest.

There was not a second's time, however, to take in what had happened. In a flash the whole horde was upon them, and Billy and Lathrop began firing desperately into the mass of foemen who appeared to spring from every side of the clearing at once.

Even in this extremity a strange thought flashed across Billy's, mind:

"Where was Professor Wiseman?"

CHAPTER XII

IN THE HANDS OF SLAVE-TRADERS

The ebon form of the Krooman giant seemed everywhere at once.

In the moonlight his terrible axe flashed incessantly and every time it fell a shriek or a muffled groan showed that it had found its fatal mark. The huge form of the warrior black seemed, however, to bear a charmed life. Again and again one of the attacking force would fire at him, but the bullets seemed to be warded off by some supernatural force. He was immune alike to bullets and arrows—with which latter the natives attached to Muley-Hassan's force battled.

Billy and Lathrop fought with unflinching courage, pouring out a leaden hail into the onslaught that again and again seemed as if it must drive the attacking force back. But fighting at such desperately uneven odds could not in the nature of things last long. There came a minute when Billy, turning to reload, found that before he could snatch up a handful of cartridges a huge Arab was on top of him.

Lathrop's clubbed rifle struck the fellow helpless the next minute and sent his long, cruel knife with a ringing crash to the floor.

Before Billy's half breathed "Thanks, old man," had left his lips, however, another of Muley-Hassan's followers had rushed in and the moment would have been Lathrop's last but that Billy drove his fist into the fellow's face with a crashing blow that knocked him on the top of his fallen comrade. It was hand-to-hand fighting then with a vengeance. Billy seized hold of the muzzle of an Arab's revolver as it was thrust into his very face, and twisted it upward as it was discharged. Seizing up a camp chair Lathrop swung it round his head like a club and scattered the brains of a native follower of Muley-Hassan.

But strategy was to put an abrupt end to the fight even if it could have continued much longer.

Billy was bleeding from a cut over the forehead which blinded him, and Lathrop had got two nasty knife thrusts, one in the arm and the other in the fleshy part of the calf of his leg, when they were suddenly attacked from the rear by half-a-dozen slavers. The next minute, wounded and bound, they were as helpless as two captured puppies.

The fight was over, but the Arabs had come out of it with a badly crippled force.

Of the twenty-five men who had attacked the adventurers' camp ten had been killed outright and half a dozen others so badly wounded that they could not move. Hardly one of them had not received some minor injury, and the very fact that they had made such a poor showing against two American boys and a Krooman armed only with an axe, filled Muley-Hassan with savage rage.

Furiously the slave-dealer ordered the two boys brought before him. A huge fire had been lighted by his followers and in the glare cast by this he received them. It was a wild scene and the two boys hardly knew whether they were awake or dreaming, as they were roughly hustled into the presence of their captor.

Diego de Barros, his cruel, thin lips curled in a sneer that showed his yellow teeth, stood by the side of Muley-Hassan, the latter a tall determined-looking man with a crisp, curly black beard and a sinister cast of features. A long burnoose of white, worn after the Arab style, hung from his head and framed his dark features, which were just then overspread by a frown as black as thunder.

Outside the circle of firelight lay the bodies of the victims of the Krooman's axe and the boys' bullets. All who could do so of Muley-Hassan's followers were gathered about him, as the two young Americans were brought face to face with the man they had such good reason to fear.

"So these are the young Americans?" he asked as Billy and Lathrop returned his hawk-like gaze unflinchingly.

"No, sir," spoke up Diego, "they are not. Wiseman has just told me that the Chester boys have flown in their air-ship and these are the cubs left behind to guard the camp."

At Wiseman's name mentioned in such a connection both the boys started.

"What! they have gone?" thundered the Arab chief.

"Yes, sir," stammered Diego, his coward nature aroused at the sight of his superior's fury.

"And by this time they are rifling the ivory cache. That fool Wiseman shall pay dearly for this. Bring him to me," shouted the Arab.

Desperate as was the boys' position they could not restrain a start of amazement as Professor Wiseman, his face pale as ashes to his very lips, came tremblingly forward.

"You were attached to this boys' camp to prevent by all means their sailing till I attacked the camp and made them prisoners, were you not?" demanded Muley-Hassan angrily.

Wiseman stammered something in reply.

"You are a coward as well as a fool," went on the slave-dealer, a cruel sneer breaking over his face; "but you have blundered for the last time. Take this fool away and kill him!" he ordered, turning away as if there was an end of the business.

Pitiful cries broke from the lips of the unhappy professor as he heard his death-warrant thus pronounced. He threw himself on his knees and begged and pleaded in a loud screeching tone for a little more time. But the chief was obdurate.

"Take him away," was all he said, and his men, not daring to disobey his orders any longer, fairly dragged the unfortunate prisoner toward the river bank. There was a short, sharp scream that chilled every drop of blood in the boys' bodies and then a splash. Professor Wiseman had paid the price of his treachery.

It was not till long after that the boys heard the full measure of his villainy. How posing as a naturalist he had wandered up and down the Ivory Coast for years acting as the secret agent of Muley-Hassan and making arrangements for the smuggling of slaves and illicitly procured ivory out of the country. He was too accomplished a rascal to be suspected and his learned appearance made it still more improbable that he should be engaged in any illegal trafficking. It was small wonder, too, that he had started when Frank mentioned the name of Luther Barr, for it was Luther Barr whom he had betrayed to Muley-Hassan and advised him of the whereabouts of the wily old New Yorker's ivory cache. As soon as he heard Frank mention the name he had of course surmised that the pretended hunting expedition was merely a blind to cover a bold dash to recover the ivory, though how they were to discover its whereabouts he could not imagine till, by prying and listening, he learned that they had a map of the locality of the stolen stuff.

He had then dispatched native canoe-men to Muley-Hassan and apprised him of the coming of the boys, and Diego had been at once sent out by the Arab to secure possession of the map if possible and, failing that, to destroy the boys' canoes. That the aeroplane would also have been put out of commission there is little doubt, if Diego or Wiseman could have found an opportunity. The brutal Arab could then have disposed of the expedition at his leisure. But the Golden Eagle II was too closely guarded for the two spies to be able to harm it.

The Kroomen porters attached to the camp had, as old Sikaso had forecast, fled into the jungle at the first attack of the Arab's followers and they did not put in an appearance till long after the marauders had left the camp.

But what puzzled the boys, as they stood facing the Arab with Professor Wiseman's scream still ringing in their ears, was "What had become of the old warrior."

He could not have turned traitor. His valiant behavior in the skirmish made that impossible to consider a minute. But it was equally certain that he was nowhere to be seen. What could have become of him? A dread that he was dead oppressed both boys as they stood there waiting for the Arab to speak.

Muley-Hassan seemed to be considering.

He twisted the ends of his jet-black mustaches like a man lost in thought, and the firelight playing on his bold reckless features showed there an expression of deep perplexity. But it was no question of mercy that was agitating his mind.

It was whether he would kill the boys right there or sell them into slavery.

To his money-making mind the latter idea commended itself. Two strong youths such as they were would fetch a good price anywhere, and so it came about that Billy and Lathrop—who had fully expected to share the Professor's fate—were flung by no gentle hands into their bullet-riddled tent and left to pass the night as best they could. Two men were posted to watch them and a rough cuff on the head rewarded Billy's single attempt to speak to Lathrop.

The next day at dawn the camp was the scene of great activity. The dead were carried into the forest a short distance and buried, while the wounded were attended to with such rough surgery as Muley-Hassan knew. In this work Diego, his lieutenant, who seemed to be a sort of Jack-of-all-trades—outside of his regular occupation of scoundrel—aided him; bandaging the cuts and extracting the bullets of his companions with some skill.

The boys were then given to eat some sort of stew in a big wooden basin and being just healthy American boys and not heroes of romance they ate heartily of the compound and felt better. Muley-Hassan himself examined the cut on Billy's forehead and Lathrop's two wounds and pronounced them mere scratches.

Just as it appeared that a start was about to be made the signal bell of the wireless rang. As our readers know it was Frank signaling from the Moon Mountains.

A sudden idea seemed to strike Diego at this. He called Muley-Hassan aside and talked earnestly with him for a few seconds, then he came up to the boy and demanded fiercely which one of them it was that understood wireless.

Lathrop replied that he did, and the next minute wished that he had bitten out his tongue before he had admitted it; for Diego, in a rough tone, ordered him to sit down at the instrument and reply that all was well at the River Camp.

"And, mind you, youngster—no tricks," he said savagely, "or I'll kill you as dead as mutton. I understand the Morse code myself and can tell what you are sending; and send slow so that I can get every letter."

Lathrop was in a quandary. To refuse to sit down at the instrument meant instant death.

He could tell that by the look in Diego's eyes and from what he had seen of him he knew he would not stop at a little thing like a murder to drive home a point.

The question was, did the man really understand telegraphy? If he didn't and was only, bluffing Lathrop determined to inform Frank of the true state of affairs. Otherwise it would do neither himself nor the others any good to try to trick Diego.

With a prayer on his lips that the Portuguese might not have been stating the truth about his knowledge of wireless the boy started to send. He had in his mind the message he would try to get through:

"We have been attacked. Get help and follow us."

But he had hardly tapped out with a hesitating finger the first word of his message when he felt a bullet whiz by his ear and the report flashed so close to him that it deafened him and scorched his skin.

"Thought I was bluffing did you, eh?" sneered the Portuguese, "come now, no tricks; send out what I tell you or the next bullet will come closer."

And so it came about that the queer hesitating message that Frank received at Moon Mountains was sent out.

Immediately it was dispatched Muley-Hassan gave the order to advance and his ragged followers, carrying the worst wounded in improvised litters, set out toward the northwest.

"We are going to the Moon Mountains," whispered Billy to Lathrop, "at least it looks that way. I overheard Muley-Hassan say to Diego that we'd have to hurry to get the ivory—"

Lathrop's reply was cut short by a scene that sent the angry blood to both boys' faces.

Before the camp was abandoned for good and the plunge into the forest began, Muley-Hassan gave a sharp order and directed several of his men set about demolishing the camp. Diego himself smashed the field wireless of which Frank and Harry had been so proud. He hacked it to atoms with one of the heavy axes. The tents and provision boxes were next piled in a heap and set in a blaze.

As the column of dark smoke rose from the ruins of the once happy camp into the clear sky the order to advance was given and the train once more moved forward.

They had hardly deserted the clearing before, from the river bank, half a hundred wild figures appeared.

They were similar in appearance—only even more wild-looking than the savages fought off by Frank, Harry and Ben the previous day. Like the others their slashed and scarred faces and clay-daubed lips showed them to belong to one of the fierce cannibal tribes of the Bambara region.

Their leader, a tall, thin savage of exceptionally repulsive appearance, motioned with his fingers to his thick lips for absolute silence among his followers.

Clutching their great broad-headed war-spears the next moment the savages slipped into the forest in the direction the Arab and his band had gone. Steadily they advanced with the quiet stealthy tread of panthers on the track of their prey.

CHAPTER XIII

GORILLAS—AND AN AERIAL TOW-LINE

The mystery of the man on the hill bade fair to be an unsolved one, for although the boys watched for some time with considerable anxiety he did not reappear. This feature of the incident set them to comparing notes and they found that their impression of the apparition differed considerably. Both Frank and Harry were ready to swear that he was a black man, while Ben Stubbs was equally convinced that his skin was of a reddish hue. All three, however, agreed that he was weaponless so far as could be seen, and his attitude appeared to be more one of interested curiosity than of actual hostility.

"Well, there's no use wasting time in speculation," said Frank at last, "more especially as it does not look as if we can get any nearer to solving the problem in that way. The thing to do now is to get at the ivory and that as quickly as possible. If that man is the forerunner of a band that means to attack us, it is all the more reason that we should get a move on."

"Right you are, Captain," assented Ben, "and here goes!"

With a mighty swing of his pick the former prospector dislodged a pile of the rough stones of which the cairn was composed and the boys, too, laid on with a will. In an hour or so all that was left of the once lofty cairn was a few big rocks.

Excitement ran fairly to fever heat as the last obstruction that lay between the adventurers and the ivory hoard was cast aside.

In a few minutes now, if all went well, they would be in possession of the treasure. More than once as they worked, Frank drew his field-glasses out of their case and scanned the surrounding wilderness of rocky chasms and swept the green jungle that lay stretched like an emerald ocean far below, but each time he replaced them with a sigh of relief. So far there was no sign of any rivals' approach, although Frank well knew that by this time Muley-Hassan must be upon his way to contest the boys' claim to the ivory.

As the last stone was chucked aside with a mighty heave by the combined forces the perspiring adventurers broke into a hearty cheer.

Beneath it was a wooden trap-door which had a ring placed in the middle evidently for the purpose of lifting it. Frank gave it a heft, but the weight was too much for even his wiry muscles; but when Ben and, Harry assisted him the door gave with a jump that threw them all to their feet.

Scrambling up in a second they rushed to the edge of the hole revealed by the uplifting of the wooden cover. What they saw showed them instantly that their wildest hopes had not been overdrawn. There, at their feet, lay a king's ransom in yellow ivory.

From the hole rose a fetid, sickening odor that at first was almost overpowering. It came from the rotting flesh that still adhered to the roots of many of the huge trunks.

With a cheer Harry was about to spring down into the aperture when Frank, with a quick exclamation, drew him back.

"Jump back for your life!" he shouted.

Harry was accustomed to obeying his brother in everything, and jump backward he did with an agility that would have done credit to a gymnast. Before he could ask a question Frank's revolver cracked and a little spit of dust shot up almost at his very feet.

There lay a tiny snake viciously wiggling about in its death agony, pierced through by Frank's bullet.

It was a rock adder—one of the deadliest of African snakes. Barely more than three inches in length, and a dull gray in color, it was small wonder that Harry in his excitement had not seen it as he was about to jump almost upon it.

"We shall have to be careful," said Frank, as he kicked aside the still writhing body of the disgusting looking reptile. "There is just a chance that Muley-Hassan, with the cunning of an Arab, may have put several more of those customers in here to guard his ivory."

It was therefore cautiously that the boys proceeded to work at getting the ivory out of the hole and although they killed three more of the venomous reptiles it seemed more probable that they had got in by accident than that the Arab slave-dealer had deliberately placed them there. By mid afternoon a big pile of ivory lay ready for transportation to the Golden Eagle Il and only a few more tusks remained in the hole.

"How are we ever going to get the tusks down the hill to the Golden Eagle II?" asked Harry as he gazed at the formidable pile.

"I have a better plan than that," replied Frank, "we will bring the Golden Eagle II here."

"What?" gasped both his listeners.

"Why not? It will be a ticklish job to land her on this spot, but I think I can do it. I mean to try anyhow."

"You are risking breaking up the ship," objected Harry.

"On the other hand, if we don't get this ivory out of here in jig time Muley-Hassan will be here with a big force and we shall assuredly all have our throats cut."

This argument proved insurmountable, and while Ben was left by the ivory Harry and Frank hurried down the steeps to the plateau on which they had left the Golden Eagle II. It was the work of a few minutes to tune her up. In a brief time from the moment they had left the ivory cache, considering the clamber they had had, the boys were in the air and headed for the spot where they had left the hoard.

But as they rose into the air they were startled by the sound of a shout and then another and another, then carne a volley of shots.

What could be the matter?

The shooting evidently was taking place at the spot where they had left Ben to guard the ivory.

Muley-Hassan! was the first thought that shot through Frank's brain.

The next minute, however, he dismissed the idea as absurd. The Arab, even by the swiftest marching, could not have reached the Moon Mountains in such record time unless he also had an air-ship, which Frank knew was impossible.

As the ship soared higher and rushed straight as an arrow through the air to the ivory cache a strange sight was revealed to the two young voyagers. High up on the mountain-side they could see Ben struggling with what appeared to be dozens of naked savages. The boys could see his gallant resistance as he swung his clubbed rifle again and again at his savage opponents. Several of them lay dead on the ground about him, but those that remained were attacking him with what seemed demoniacal fury.

"Good Lord," gasped Frank, "what on earth can have happened?"

"They're cannibals!" gasped Harry.

"No—no," exclaimed Frank hastily, "they're—give me the glasses quick, Harry—that's right—I thought so. They're not savages, but worse almost."

"What do you mean?"

"That they are gorillas!"

At her utmost speed the big aeroplane bore down on the scene of the unequal combat between Ben Stubbs and the savage beasts.

The boys could see that one of the brutes had seized their stalwart companion's rifle from him and with incredible strength had broken it in half as if it had been a wooden toy. The next minute Harry's rifle spoke and the gorilla that had just performed the miraculous feat of strength fell dead. With a shriek of rage the others turned to see whence came this new enemy.

At the sight of the great aeroplane bearing down upon them they at first started to flee with howls of terror, but the next minute they rallied and with low growls of rage, that bared their cruel fangs, they deliberately waited to see what this strange object might be.

This gave Ben a brief respite and he occupied it by reloading his revolver. The boys were delighted to see by this that their brave comrade was not seriously injured.

But now the Golden Eagle II was ready to settle and Frank, guiding his aerial steed with one hand, grasped his revolver with the other, for it was evident that the rush would come as they struck the ground. And come it did. As the wheels of the aeroplane struck the earth and Frank threw in the brakes sharply crashing into a rocky wall, with a howl of defiance the whole horde of man-like brutes rushed down on the air-craft with wicked rage in their spiteful little red eyes.

The leader of them, a huge "old man" gorilla, brandished an immense stone which he hurled with vicious energy at the new arrivals. Luckily it fell short of the air-ship or it would have crashed through the plane covers and have seriously crippled, if not ruined, the air-ship.

The boys' rifles cracked simultaneously and two of the attackers rolled over, with horrible human-like cries, but the leader, the bad "old man," was still in the field. As he saw his fellows fall he gave a mighty yell of rage and hatred that seemed to come from the depths of his hairy chest, and beating rapidly on it, as if it were a war-drum he rushed straight at the aeroplane.

"Don't let 'em get near the engines," was all Frank had time to shout before the avalanche of hairy, ill-smelling brutes was upon them. Some of them had armed themselves with rocks which they hurled with ferocious force. Others used nothing but their bare hands. Some of them, wounded as they were, fought with added fierceness. Desperately the boys fought them off and when the magazines of the rifles and revolvers were emptied they fell back on their hunting knives.

Frank had made a furious lunge at the "old man" and missed him by a hair's-breadth when he felt two great hairy arms encircle him from behind and the hot breath of one of his horrible opponents whistling savagely in his ear. He tried to lunge backwards at the creature, but toppled over and fell sprawling. In a flash the "old-man" gorilla was on him when Ben's revolver cracked and the "old-man," badly wounded, sprang high into the air and rolled over and over, clutching his head with both his huge hands and screaming in an agonized manner.

The fall of their leader seemed to discourage the others. They fought on for a while but it was half-heartedly. The boys had had time in the brief pause that followed the killing of the "old-man" to reload, and with their rifles newly charged they were in position to make terrible reprisals on the gorilla band for the mischief they had wrought. The monsters evidently were about to quit the battle when suddenly a cry rang through the air that ended the fight more abruptly than even the boys' bullets could have done.

"Ah-o-o-o-o-AH-O-O-O-O-o-o-o-o-o-o-o-o-o-o-o!"

It was the voice of the mountain once more.

With yells of dismay and terror the remainder of the gorilla band instantly dashed up the rocky mountain-side dragging with them, in grotesquely human fashion some of their wounded. Several of these, however, still lay on the ground and the boys put them out of their misery with a few well-directed shots. A pathetically human look lingered in the eyes of some of the injured gorillas and Harry burst out with:

"This is awful work. I'd rather fight a dozen bands of cannibals than have to do this."

"And yet," replied Frank, "if we hadn't killed them they'd have killed us."

At last the unpleasant work was over and the ivory was rapidly loaded into the aeroplane. But here an unanticipated difficulty manifested itself. Obviously the aeroplane would be too heavily laden if she attempted to carry all or even a good part of the ivory.

"Now we are stuck," cried Harry.

"Hold on," exclaimed Frank with a smile, "I anticipated this. We are going to turn the Golden Eagle into a tow-boat."

"A tow-boat?"

"That's what I said."

"What do you mean?"

Frank, in reply, bent over the stem-locker of the aeroplane and drew out what Harry instantly recognized as the silk envelope of an experimental dirigible they had built the year before.

"Now then," said Frank, "give a hand here."

They all three pulled and hauled till the envelope was spread level on the ground, all folds and creases having been carefully shaken out.

"Well," said Harry, "this would carry an awful weight of ivory, but how are you going to inflate it?"

"With these cylinders," was the answer as Frank opened the store-room below the floor of the Golden Eagle and pointed to a dozen cylindrical steel receptacles. "They contain more than enough pure hydrogen gas at a high pressure," he explained, "to inflate the bag."

In his enthusiasm Harry waved his helmet and Ben did the same.

"An aerial express, hurray!"

The inflation hose was soon connected to the first of the cylinders and with a hiss the gas rushed into the bag when a turn of the wrench set free the precious stuff. Slowly the big yellow envelope swelled and assumed shape until by the time the last cylinder was empty it was tugging and straining to rise. But the boys had weighted it down with rocks and pegged its net ropes to the ground.

The ivory was loaded into a sort of rope basket, like those used to hoist cargo aboard a ship, and in a short time, so quickly did they work, they were ready for the air, so far as what Harry called "the airbarge" was concerned.

"We shall have to strip the Eagle," decided Frank, when the inflation job was finished.

"Of everything that we can spare," added Harry, setting to work at once to rip the transoms and detach the bolts that held the heavy wireless apparatus in place. As he did so, Frank was moved by a sudden thought.

"Hold on a second, Harry," he shouted, "I'll call up the river camp before we cut off all communication."

Rapidly he sent out the call. Again and again his nervous finger agitated the key—but there was no response.

"They—they don't answer," gasped Frank at last—heavy anxiety in his tones.

"Oh, Frank, do you think anything serious is the matter?" cried Harry.

"It may only be that the apparatus is out of order," replied the elder brother seriously; "but it looks bad. That field wireless was in prime condition and it would be next to impossible for them to fail to receive our call."

"Well, there is only one thing to be done," remarked the practical Ben Stubbs.

"And that is—?" queried Harry.

"To get back there as soon as possible, for if they need us they need us dern bad," was the energetic reply.

Half an hour later the Golden Eagle, stripped of all her heavy gear and only carrying just enough gasoline to get her to the river camp, where the adventurers expected to find a reserve supply, rose slowly into the air with her queer tow tugging behind on the wireless ground rope. The boys had cached the wireless apparatus and the other gear, to be called for at some more opportune time. To their great regret, also, they had had to leave some of the ivory behind them. But the majority of what they did not dare trust to the gas-bag they carried in the chassis. Luckily for them there was hardly a breath of wind and the novel carrier towed well.

As the occupants of the great aeroplane gazed back at the sinister Moon Mountains as they fast faded out—they saw silhouetted against the evening sky a dark figure.

It was recognized at once as one of the beaten gorillas scouting to see if the terrible white men had really gone.

"There's the man we saw this afternoon," laughed, Frank, as with rapidly beating propellers the Golden Eagle II winged her way with the convoy toward the River Camp.

CHAPTER XIV

AN ESCAPE—AND WHAT CAME OF IT

From the pace at which Muley-Hassan's band traversed the jungle paths it was evident to the two young captives that there was imperative need in Muley-Hassan's mind of arriving somewhere at a set time. The usual noonday rest, which even the avaricious slave-trader was in the habit of taking, was not observed and the travelers pressed straight on. Lathrop and Billy were almost ready to drop with fatigue when that evening, just at dusk, they arrived at the bank of a muddy river which Muley-Hassan, impatient as he was to proceed, decided it would be unwise to ford till daylight—when they could look for a good crossing place. At the spot which they had halted, the stream—swollen apparently by rains in the mountains—roared between its banks, in a dark chocolate-colored flood.

Muley-Hassan himself was the only one of his band provided with a tent, or anything resembling one, and the boys shared the common bed of the rest of the party—which was the ground. A more unwholesome resting-place in Africa, particularly on the steamy, swampy banks of a river, could hardly be imagined. So indeed Muley-Hassan seemed to think, for after a short time, during which the boys vainly tried to secure some sleep, he ordered Diego to provide them with blankets to place between themselves and the bare earth.

"I expect to get a good price for them eventually," he said, "and I don't want to lose them unless I have to."

As the boys' wrists and ankles were bound with tough grass while there was no particular attempt made to watch them, and soon the snores of the camp bespoke that it was at rest. Then it was that Billy whispered to Lathrop.

"Now's our time to try for it!"

"Try for what?" whispered back Lathrop in an inert tone.

"To get away."

"What!"

"I mean it. I found a sharp stone imbedded in the ground near to me and I have nearly sawed through my wrist-bands."

After a few seconds' more vigorous scraping against the stone, Billy whispered:

"My hands are free. Wait till I wiggle my fingers and get up some circulation and then we'll make our attempt—"

When he had once more got full control of his cramped fingers Billy stooped cautiously over and loosened the thongs about his ankles. So tightly had they been drawn, though, that it took some little time to get the cramps out of them. At last, however, the boy succeeded in restoring the circulation and then he was ready for the most daring step of his attempt. Cautiously he fell on his hands and knees and began to crawl toward the nearest of the sleeping slave-traders.

"What are you going to do, Billy?" asked Lathrop, in an agony of fear lest the man should awaken.

"Watch me," was the young reporter's reply, as on his stomach he wiggled painfully across the few yards separating him from the sleeping man. In reality it took only a few minutes, but to both the boys the period of time occupied seemed interminable.

But it was no time to hurry things. One false step night cost them their lives and Billy realized this.

With the slow deliberate movement of a snake he, reached out his hand when he got near enough and took from the sleeping man's side his long curved Arab scimitar. Then he glided back to Lathrop as silently as he had left.

He had just reached his resting-place when there was a stir from the further side of the camp. Like a rabbit ducking into its hole Billy was under his blanket and apparently fast asleep in a second. But his heart beat so loudly that it felt to him that anyone who was not deaf could hear it a hundred yards away.

The man who had moved was Diego and the boys could hear his cat-like footfalls as he neared their sleeping-places. Once he stumbled over one of the sleeping men and the aroused one rose with a start and called wildly:

"What is it?"

"Hush, Adab," cautioned Diego, "it is I—Diego. I'm going to give an eye to those two American brats."

"They're tied up hard and fast enough," chuckled the other.

"If they were of any other nationality—yes;" was Diego's reply, "but these Yankees are brave and clever enough to escape from almost any trap."

"You bet we are," thought Billy to himself, giving a realistic snore.

Although he did not dare to open his eyes, the young reporter could feel Diego standing over them in the moonlight and gazing down at them to ascertain if they were still "hard and fast," as the other had expressed it.

For an instant a terrible thought flashed across Billy's brain.

"Suppose Diego should take an idea to examine their thongs?"

But the lieutenant of Muley-Hassan apparently was satisfied, for after a few minutes' scrutiny he turned to go Billy could hear his feet scrape as he swung around.

At almost the same instant the night was filled with savage cries and the camp was thrown into confusion by an onrush of wild figures before whose spears the half-awakened Arabs were slaughtered like sheep.

Not realizing in the least what was happening, Billy yet conjectured that the Arabs were just then too busy to pay any attention to himself and Lathrop. With two slashes of the stolen scimitar he severed Lathrop's bonds and dragging him to his feet dived into the forest.

As they entered its recesses a fleeing Arab, still clutching his rifle, dashed by them and an instant later fell dead. He had been speared through the back.

Billy, with a quick inspiration, seized the dead man's long rifle and his ammunition pouch and, followed by the bewildered Lathrop, plowed desperately forward into the screen of the jungle.

Behind them they heard cries for mercy and fierce shouts from the attacking savages. At first the cries and imprecations of the slave-traders predominated and then, by the altered sounds that came from the scene of the fighting and the crashing of the Arabs' volleys, the boys realized that the tide of battle had changed and that the Arabs were driving back the attacking force.

"What do you suppose happened, Billy?" asked Lathrop, only half awake, as the boys, with the fleetness and endurance that desperate need lends, plunged deeper and deeper into the forest.

"Why, that some cannibal tribe that Muley-Hassan pillaged for slaves at some time has trailed him and attacked him," hazarded the reporter.

How near he came to the truth our readers know. The band that had made the midnight attack was the same that had painstakingly trailed Muley-Hassan since he destroyed the boys' camp on the river bank.

"But the Arabs have beaten them off?" queried Lathrop.

"Evidently," replied Billy, as the volleys died out and victorious Arab shouts were beard. "Hark at that! It's really too bad. I'd like to have seen old Muley and his precious band driven into the river. But if they have driven off the savages they'll be thinking about chasing us."

As he spoke there came a low, growling sound that seemed to proceed from some distance, but nevertheless filled the air. It rumbled and rolled above them like—

"Thunder!" exclaimed both boys in the same breath.

"We've got to find shelter of some kind, quick," exclaimed Billy; "these tropical storms are unlike our little disturbances, and if we get caught among these trees in one, of them we stand a good chance of being killed. It looks like we've jumped out of the frying-pan into the fire."

Without the least idea in which direction they were proceeding, the two chums struggled bravely on, Billy encouraging the flagging Lathrop from time to time with a joke, though these latter were, as Billy admitted to himself:

"Pretty dismal!"

At length, just as dawn was beginning to break, they found themselves facing a steepish cliff of rough rocks.

"Well, here's where we turn back," remarked Billy, bitterly discouraged nevertheless.

If they were lost in this equatorial forest, what chance did they stand of ever seeing their home and friends again?

As for Lathrop he sat down on a rock overgrown with a kind of monstrous lichen and gave way to tears. But not for long. Lathrop was a plucky enough lad, and as Billy truthfully remarked:

"We are going to have enough water before long without our turning on the weeps."

So Lathrop braced up and the boys looked about them. To their intense joy they soon spied in the rocks, a short distance from where they then were, a dark hole partly overgrown by creepers, which was evidently the entrance to a cavern. At the same instant there began a mighty pattering on the leaves of the dense tropic growth all about them, and a louder growl of thunder announced that the storm that had been heralded a few hours before was about to break.

"Well, me for that African Waldorf-Astoria," cried Billy, grasping his rifle and making a dive for the hole. Lathrop followed him and as soon as they were inside the cave he lit a match from his waterproof box.

"Looks to me like there might be snakes in here," he whispered, awed by the darkness and silence of the place.

"Rats," laughed Billy, although he himself felt by no means sure that at any moment some scaly monster might not descend from the roof; "but I'll tell you what we'll do. Light a fire."

"How are we to get wood?" asked the practical Lathrop.

"There's plenty of it right at the mouth of the cave. I'll get a few armfuls and in a minute we'll have things snug."

The young reporter hastened to the cave mouth and in a few trips had gathered up several huge armfuls of wood-drift of all kinds from under the great trees all about. He was just re-entering the cave when there came a flash of blinding light so brilliant that it seemed as if the sky itself had split wide open. A bluish glare enveloped the forest and the lightning flash was instantly followed by a crash of thunder that shook the ground under the boys' feet.

"Well, they don't do things by halves in this country," remarked Billy as he re-entered the cave after a second of being temporarily stunned by the terrific flash.

It didn't take the boys long to have their wood in a blaze and as the smoke did not, as they had feared, fill the cavern, they assumed that there must be some opening above through which it escaped. This fact they verified shortly when, after the storm had been waxing in fury for half-an-hour, a perfect torrent of water came tumbling in from the rear of the rocky cavern.

"Hark!" exclaimed Billy as the boys busied themselves trying to scrape out a water-course that would divert the flood from their fire. From far in the rear of the cave came a plaintive sound of "Mi-ou, Mi-ou."

"Cats!" cried Lathrop.

"Cats nothing," was Billy's scornful reply; "here, let's have a look."

He seized a blazing brand out of the fire and hastened to the place from which the sounds emanated.

"Come here, quick, Lathrop," he cried. The younger lad scurried back and found Billy bending over a roughly constructed nest or bed. On it lay four tiny, fuzzy yellow things. They were "meowing" at the tops of their voices as the torrent of water that had annoyed the boys dripped into their snug nesting-place. At the same instant the boys became aware of a sickening odor of decaying flesh.

"Come on! we've got to get out of here quick as quick as we can," exclaimed Billy as they hastened towards the fresh air.

"Why, what is it, Billy?" asked Lathrop.

"I don't know; but I think that those are lion cubs—they look like the ones I've seen in the Bronx Zoo," was the young reporter's reply, "and if they are, this is no place for us. Come on—the storm is letting up. Let's get out quick before the old ones get back."

The storm, with the suddenness with which these furious tropical disturbances arise and vanish, had indeed gone and the sun was shining down once more on the drenched jungle, which glittered with diamond like spangles as the rays struck the dripping fronds and branches. But the boys had no eyes for the scene about them, beautiful as it was, for as they emerged from the cave a low growl greeted them.

Crouched on the ground—her tail lashing the earth like a cat's when it is about to spring—was a huge tawny lioness—her cruel green eyes fixed full upon them.

CHAPTER XV

THE FLYING MEN

For a breath the boys stood petrified and then Billy hastily slipped a cartridge into the rifle he had taken from the dead slave-trader. But even as he did so the lioness curved her lithe body, as if her backbone had been a steel spring, and launched her great form through the air.

That minute would have been Billy's last—for in his excitement he pulled the trigger before he had brought the rifle to his shoulder and the bullet whistled harmlessly into the air—but for a strange thing that now occurred.

While the tawny brute was in mid-spring, her cruel claws outspread to maul the unhappy reporter, a great spear whizzed straight at her and buried itself in her heart just behind the left shoulder. With a howl of pain the brute fell short in her spring and, before she could make another attack, Billy had reloaded and sent a bullet crashing between her eyes. As the lioness rolled over dead, the tall form of a. savage sprung out of the jungle and stood for a second gazing at the boys, as much astonished, it seemed, at them as they were at him.

Billy, seeing that the best plan was to be pacific, threw down his rifle and cried:

"Seesenab," (peace); the word be recollected hearing the big Krooman use the day that he attempted to take his unlucky photographs.

"Seesenah—white boys," replied the other, the latter words in fair English and in a deep guttural tone, coming forward with the head of his other spear held downward in token of peace. "From where come the white boys—what do they in our land?" was his next question.

"We are lost," explained Billy, "and we are also, blamed hungry," he added, in a burst of confidence.

The savage smiled and rubbed his stomach.

"That's the idea," cried the irrepressible reporter. "Heap—empty—savee?"

The man leant over the dead lioness and, using his spear-point as a skinning knife, rapidly stripped her of her hide. Then, swinging the pelt over his shoulder he motioned to the boys to follow him.

"I don't know where the dickens he means to take us," confided Billy to Lathrop as they obediently trailed along behind, "but so long as we get something to eat I'm so hungry that I don't care if we get eaten the next minute."

"That's just the way I feel," agreed Lathrop, "and anyhow he seems to be a pretty decent sort. He saved your life, that's one thing sure."

"I guess I'll never make a mighty hunter," said Billy dolefully, "there was a chance to make real Bwana Tumbo shot and I missed it."

The savage stalked along in front of them for some distance till they suddenly emerged on a small clearing by a river bank, in which a rough native camp had been pitched. The tents of grass occupied by the hunters being of a peculiar conical shape, like the pointed caps that used to be labeled "Dunce."

Much excitement was created by the arrival of the two boys and their companion, and the hunters crowded round the chums while their guide explained with a wealth of gesture the incident of the killing of the lioness, and also the fact that the boys were very hungry.

Several of the men instantly filled wooden bowls with something from a pot that simmered over the fires and the bowls were thrust before the two ravenous boys. As there were no forks of course the boys used their fingers. But this did not interfere with their appetite and after they had put away two bowls apiece the savages' opinion of them evidently rose considerably. Among the West African natives a big eater is esteemed as a mighty man. Lathrop was considerably embarrassed, however, while he satisfied his hunger by the attention the hunters bestowed on his red hair. Several of them came up behind him and rubbed their hands in it as if they imagined it possessed some sort of medicinal value. Had any one at home dared to take such liberties with the boy's rubicund locks there would have been a fight right away, but Lathrop felt that the best policy to assume in the present situation was silence, and as the old ship captain said to his mate, "dem little of that."

"I say, Billy," whispered Lathrop suddenly, as, after eating the stew, they watched the hunters piling their belongings into their canoes, "you don't suppose they mean to fatten us up to eat us, do you?"

"Well, we can't starve even if that is the reason," replied the practical Billy, "but so far they seem friendly enough. They have not even taken my rifle away."

"That looks encouraging, certainly," replied Lathrop; "if only we knew where Frank and Harry and good old Ben were we might find this all very interesting, as it is though—"

"We've got to make the best of it," chimed in Billy, "come on. See old job-lots is signing to us to come down and get in a canoe."

"Whatever they mean to do with us they seem determined to make us comfortable," remarked Billy, as the boys took their seats in a canoe in which skins had been piled to make an easy seat.

For most of that afternoon they paddled steadily up the brown river, the savages singing from time to time an unending sort of chant, that sounded like nothing so much as a continuous repetition of:

"I-told-you-so. I-told-you-so. I—told-YOU-SO."

"Hum," commented Billy, "if anyone had told me so I'd have stayed in New York."

At length after what seemed endless hours of paddling and chanting the river took an abrupt turn and the boys found themselves at the foot of a steep cliff that towered up, it seemed, for six hundred feet at least. It was formed of black basalt and was crowned with a fringe of contrasting vegetation, but the most remarkable thing about it was that its surface was literally honeycombed with small holes from which, as the canoe cortege drew up, innumerable heads were poked.

An astonishing thing, however, about the men who scrutinized the lads from their lofty watch-towers, was that they were several degrees lighter in complexion than the boatmen and almost as white as the boys in fact. Their features, too, were different. As the boys looked in wonderment at this extraordinary dwelling-place and its equally strange inhabitants, Billy gave an excited shout:

"Great jumping horn-toads, look at that!"

One of the light-colored men had emerged from his, hole and with as little concern as if he were taking a walk had suddenly launched himself into space. But instead of falling to the ground or into the river, as the boys had fully expected to see him do, he floated gracefully to the opposite bank of the river with as little effort as a settling bird.

"Good land of hot-cakes, Lathrop, do you realize where we are?" almost shrieked the excited Billy.

"In the village of the Flying Men," stammered Lathrop, as, one after another, the inhabitants of the rock holes dropped from their aeries and floated groundwards. As the boys watched they saw distinctly that each man, from his wrist to his side, was possessed of a sort of leathery fiber like that of bat's swing, and that as their arms were of unusual length this fiber supported them in their downward flights like a parachute.

"I'll never call any one a liar again as long as I live," choked out Billy, as one after another these strange beings gathered in a chattering group on the river bank.

"But they can't fly upward," exclaimed Lathrop, pointing eagerly to where some of the gliders, having swum the river, were nimbly clambering up a grass rope-ladder to their homes.

"Oh, gee! if I only had a camera," groaned Billy.

"It will be no use telling anyone about this even if we do get out of here, they'll say that we have had a rarebit dream."

"That's so," assented Lathrop, "and honestly, Billy, are you sure we are awake?"

"Sure," replied the reporter giving himself a vicious pinch, and exclaiming "Ouch!"

But there was no time to talk further. Their guide now came up to them and jumping into their canoe paddled them to where the end of the rope-ladder dangled in the stream. He pointed upward for them to ascend. But Billy's curiosity would not let him mount before he had asked a question.

"Who are these people?" he asked in, for him, an awed tone.

"Very old-time people," rejoined their guide. "We hunt for them, work for them. They the same as fetish."'

The boys mounted the ladder slowly.

Unused as they were to such a contrivance it required all their nerve to keep on going up, as they swung at a higher and higher altitude above the river. Neither of them dared to look down, as they were certain that they would be overcome by dizziness.

With their eyes glued to the rock in front of them, they mounted what seemed to be endless rungs till at last they found themselves at the top of the ladder and facing a large opening cut in the rock.

As they found out later, this was the main entrance to the dwelling of this strange community and from it various galleries and passages branched off to their separate dwelling-places. Each family lived in a rock house exactly adapted to the size of the circle. There were six stories, so to speak, of these dwelling-places, but they all communicated, either by means of stair-ways cut in the rock or inclined galleries, with the main passage at the entrance of which the chums now stood.

Their guide, who was immediately behind them on the swaying ladder, took the lead as soon as the three stood side by side on the summit, and escorted them down the long passage. Before they started he took from a bracket in the wall a kind of torch, made of some resinous wood unfamiliar to the boys. Striking piece of flint against his spear blade he soon produced light and holding the torch high above his head, so that its light shone on the walls, rendered glossy by the rub of uncounted ages of greasy elbows and bodies, he led the way down the passage. The boys could feel that after walking a short distance it took a sudden rise and yet further a cool wind began to blow in their faces.

About a hundred yards from the spot where they first noticed the air stirring in their hair the boys and their guide emerged on a scene whose beauty at first shock almost took the lads' breath away.

Before them stretched a fertile valley neatly divided into patches—each hedged off in squares in which flourished all sorts of vegetables, including sweet corn and potatoes and several other less familiar varieties. In pastures, fenced in with mathematical regularity by hedges of the African cactus thorn, herds of humped cattle were feeding contentedly in the mellow glow of the setting sun, occasionally lowing softly, which latter made Billy, as he expressed it, "long for the old farm."

The Winged Men likewise cultivated, it seemed, fruits of many kinds and had also stockades in which poultry, of breeds strange to the boys, but undoubtedly sprung from the aboriginal African fowl, were abundant.

It seemed as if they had struck a land in which the inhabitants lived an ideal life, surrounded as they were by every comfort and necessity that one could imagine; but that even they were distressed by the raids of enemies transpired when the boys' guide, whose name they had learned by this time was Umbashi, pointed to the west in which the setting sun was now kindling a ruddy glow and said:

"Sometime elephant come—then much trouble."

Of the full significance of those words, however, neither boy dreamed as, after a supper of fresh corn, bitter melon, stewed deer meat and a dessert formed of some sort of custard they sank to sleep on their couches of skins, spread for them by Umbashi's direction in a vacant dwelling in the cliff face.

Their slumber senses carried them back to New York and Billy was in the midst of escorting Umbashi in full war paint through the office of the New York Planet, followed by hordes of joshing reporters and inquisitive office boys, who wanted to know whether he'd match his dusky friend to fight Jim Jeffries, when he was awakened by Umbashi himself, who in a few words told him it was morning and time to get up and dress swiftly, as the King of the Flying Men wanted to see him and his young companion at once.

CHAPTER XVI

FOOLING AN ARAB CHIEF

"Frank, what do you make of it?"

"Harry, I don't know what to think."

"Ain't nuffin fer it but ter keep on hopin' fer the best, as the feller said when they had a rope around his neck fer horse-stealing and was about to string him up."

The three—Frank and Harry Chester and Ben Stubbs—were standing round the charred remains of their once lively, well-equipped camp—where they had arrived that morning at daybreak after a tiresome night spent circling about in the moonlight trying to locate it—and now the reason why they had failed to see the white tents was fully apparent by their blackened sites.

"Billy and Lathrop have been carried off!" It was Harry who spoke.

"Beyond a doubt. I thought at first that the raid must have been made by cannibals, but cannibals do not carry rifles, as a rule, and look here." Frank stooped and picked up half-a-dozen cartridges of the kind used by the Arab slave-traders.

"You know there were no shells like that in our party," he went on, "but I can see by the collection of empty shells in the place where the tent stood that Billy and Lathrop must have put up a hot defense."

"Frank, do you—you don't think, do you—" Harry burst out.

"That they have been killed?" Frank finished for him. "No, I do not. Unless they fell in the fight and then we should have seen their bodies down with the others by the river. No, it is my idea that they have been carried off to be sold as slaves. They would have a high market value you know."

Harry groaned.

"But don't you think there is a chance of our getting them back?"

Frank's face grew grave.

"Of course we are going to try every means in our power, but once in the hands of that scoundrel Muley-Hassan it is doubtful if we ever see them again. There is only one thing for us to do."

"And that is—?"

"To get back to the Moon Mountains at once. But we have no gasoline."

This was a stunning blow; in the excitement their of fuel had not occurred even to the farseeing Frank. They had had, as our readers know, to leave most of their gasoline at the Moon Mountains in order to lighten the aeroplane. Without it they could not move an inch in their air-craft. Harry tested the tank. Only a few paltry gallons remained—not enough to drive the aeroplane ten miles.

As the boys stood, struck dumb by the realization of the disaster that had overtaken them, Ben Stubbs, who had been down to the river bank, reappeared.

"Look here!" he exclaimed, holding out at arms length a long white cloak. One glance at the garment was enough—it was an Arab article of dress. There was no further doubt about it, then. Muley-Hassan and his men had carried off Billy and Lathrop.

"But that's not the most extraordinary part of it," went on Ben; "while there are half a dozen of the Arabs' canoes down there, there are a lot of others, that must have belonged to a bunch of natives from their shiftless look—and I could see the bare imprint of the savages' feet in the mud, coming after the Arabs had trod around there."

This was a new mystery. Apparently, then, a tribe of cannibals had been on the trail of the Arabs who had carried off their two young companions. This could only mean one thing, that they meant to punish the Arab slave-dealers for some outrage and, while this would have been quite satisfactory to the boys under other conditions, as things were it meant that there would be a fight in which both Lathrop and Billy would probably be seriously wounded, if not killed. How wrong this surmise was we know, and it serves to show how very wide of the mark it is possible for the constructors of a theory to steer.

And here for a time we will leave our despairing friends while we go back to the Moon Mountains.

The outline of the Golden Eagle II, in her flight to the river camp, had not faded out on the twilight sky, before, through the jungle at the foot of the Moon Mountains, a strange figure pushed its way. It was Sikaso, but a changed Sikaso from the agile muscular black who had wielded his axe with such terrible effect at the fight of the evening before. His ebony body was cut and scarred with the signs of his battle with the thorns and saw-bladed grasses of the dense forest, across which he had cut in desperate haste, scorning all paths in order to warn the Boy Aviators and their chum Ben of the rapid approach of Muley-Hassan. With that strange instinct that white men in Africa recognize in certain of the natives as a sixth sense, the giant black had read in a fire kindled after the battle, that the boys were at that moment in the Moon Mountains, and had at once set out—exhausted as he was—at top speed on the long journey. Only a man of his adamantine strength could have endured the hardships and it had fatigued even his iron frame, as was evident by his stumbling footsteps as he made his way up the side of the mountain—pausing from time to time as if to listen to the whisperings of his mysterious instinct.

Billy and Lathrop, half inclined to accuse the old black in their minds of base desertion, did him a gross injustice. After he had seen the two boys taken prisoners, the old warrior had realized that he could be of far more use to them at liberty than he would be if made captive by Muley-Hassan. Indeed there was no doubt in his own mind that the Arab would put him to death instantly if he ever got his hands on him. He had therefore built a fetish fire and in it had made out distinctly Frank and Harry and Ben in their air-ship, encamped on the mountain-side, and had set out without delay at the peculiar jog-trot by which the native bush-runners can cover daily as much ground, and more, than a horse.

But the huge Krooman was doomed to as bitter a disappointment as the youths he was in search of had experienced at their return to the river camp. He found the spot on which the Golden Eagle had rested deserted, but still urged on by his strange sense of locality he finally stumbled upon the ivory cache.

"Um, big fight here," he mused to himself as he gazed about him at the mangled bodies of the gorillas which showed black as ink on the rocks in the sharp, brilliant moonlight. The heap of uncollected ivory was the next thing to attract his eye and with a guttural grunt the negro helped himself to a drink of water from his skin-bag while he sat down to ponder. He did not waste much time in reflection. Springing to his feet he vanished down one of the dark recesses of the mountain-side and was gone about an hour. When he returned he picked up an armful of the ivory—a load that would have staggered three ordinary men—and, hefting it easily in his arms, vanished with it into the dark shadows. For two hours he worked steadily and at the close of that period there was not enough ivory left about the cache to make a watch-charm of. Old Sikaso had found a new hiding place for the stuff the boys were compelled to leave.

Then he sat himself once more down on the rock, and leisurely smashing to pieces with his inseparable axe, the wooden cover that had been over the cache, he selected, with a good deal of care one of the dead gorillas. Having found the one that seemed to suit him; he cut off from its flank a hunk of meat with his keen weapon and producing a flint and steel soon had the meat toasting over a blaze. When it was done to his satisfaction he leisurely ate it and washed it down with a draught from his skin-bag. He then cooked several more pieces of gorilla meat which he tucked in his waist-band, and shouldering his axe and humming to himself his grim war-song, he set out at the same swinging dog-trot on his long trip to the river bank. With the vitality common to such men, his brief rest and refreshment had rendered his tired frame as vigorous as ever and there was no trace of fatigue in the steady trot of the ebony figure as it plunged into the dark forest and vanished.

A second later, however, the figure reappeared as a noise of voices was heard drawing nearer down a forest trail. Throwing himself on his face and lying as motionless as a fallen log, the Krooman watched as Muley-Hassan and his followers—almost worn out and sadly diminished in numbers since their fight with the boys and with the cannibals—appeared. True, they had beaten the latter off, but at great loss to themselves, and the few men that now limped forward—urged on only by the fierce voice of Diego and Muley-Hassan—appeared ready to drop in their tracks from exhaustion.

"A hundred pounds of ivory to every man of you if we get there before they have cleaned the place out," the Arab was shouting by way of encouraging his men. Old Sikaso, with a grim chuckle, watched them make their way up the mountain-side and then laughed softly to himself as their imprecations of rage and fury broke out as they reached the cache—and found it empty!

Somewhat cheered by the vigorous Ben, who proposed to paddle down the river to the nearest settlement himself the next day, if some news were not heard of Billy and Lathrop, the boys were preparing for bed that evening—the bed consisting of the floor of the Golden Eagle's stripped cabin—when they were startled by Ben holding up a warning finger.

"Hark!" he exclaimed eagerly.

The boys listened.

"There's somebody coming," were Ben's next words.

Sure enough drawing closer every minute they could hear a soft patter-patter coming down a jungle-trail and evidently, by the sound, heading for the camp.

"Who can it be?" exclaimed Frank in a low tone, not daring even to mention the wild hope that surged in his heart. For a minute he thought that it might be the missing chums, and that even Harry and, to a less degree, Ben, shared his thought he saw by their parted lips and tensely strained eyes.

In absolute silence they listened as the footfalls drew in toward them, but not by even the wildest stretch of the imagination could they make out more than one man's footsteps.

Instinctively each member of the party raised his revolver as the bushes parted and from them tottered a man who was very evidently in the last stages of exhaustion. The figure staggered forward to the aeroplane as the boys and Ben lowered their revolvers, seeing that, whoever the newcomer was there was no fear of violence from him. It was Ben who recognized him first:

"Sikaso!" he cried, as the figure crumpled up in a heap, completely exhausted.

The boys rushed to the fallen man's side as they heard the name. They bathed the huge black's head with water and after a few minutes he opened his eyes and recognized them with a faint smile. After he had been given some nourishment he completely recovered from his spell of weakness which he called:

"Big fool—all same woman," quite omitting to state that he had traveled almost eighty miles since the preceding midnight.

The boys sat late listening to what the black had to tell of the attack on the camp—of Professor Wiseman's treachery and death—and of the carrying off of the boys. Then Sikaso went on to gleefully relate, while they warmly clasped his mighty hands, how he had hidden the rest of the ivory and how he had seen Muley-Hassan pass on his way to the rifled hiding place.