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SERCOMBE GRIFFIN

THE CRIMSON CATERPILLAR

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First published by Sampson Low & Marston, London, 1935

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Dust Jacket of "The Crimson Caterpillar,"
Sampson Low & Marston, London, 1935 (restored)


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Cover of "The Crimson Caterpillar,"
Sampson Low & Marston, London, 1935


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Title Page of "The Crimson Caterpillar,"
Sampson Low & Marston, London, 1935


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TABLE OF CONTENTS



CHAPTER I
THE TRADER WHO LAUGHED

GASTON JAMBONNE rotated his thumbs as he nursed his hands on an ample paunch. He laughed loudly as two youths were shown into his office by a coal-black Kabyle of gigantic stature. Jambonne laughed loudly; but he did not smile.

"Hahaha! Now that we three are quite alone, shut off from all the world, we can talk. It is a great delight to see you—two so gallant youths of the two great races of Europe. Hahaha!"

The Algerian half-caste spoke in French, and laughed like no one else that Tony Mase had heard hitherto.

The English boy, as familiar with French as with English, fixed his dark eyes on the speaker; the laugh might be meant as a welcome, but Tony missed the smile that should accompany every laugh.

Gaston Jambonne shot a glance from out crafty eyes at the English boy, then extended a pudgy hand towards the French youth.

"Shake hands, my brave Henri. You come to sign the contract, yes? It is a great exploit you undertake—a journey that may astonish the world. Hahaha!"

Henri Leprince's eyes gleamed with satisfaction. Cousin of Tony Mase, he was a generous-hearted Frenchman, with all the gaiety and gallantry of his nation. The French youth told himself he had every reason to be satisfied. He had established his strange occupation at length; Jambonne had entrusted to him an undertaking that would establish his fortunes.

"Verily, Monsieur Gaston Jambonne, we will prove ourselves your trusty couriers across the Great Desert," cried the French youth. "And we will prove to you the wondrous worth of ma chère Crimson Caterpillar."

The Crimson Caterpillar of which its owner was so proud was a wonderful little motor car specially built for desert traffic. Only the previous year the Sahara had been crossed by motor cars for the first time—motor cars fitted with chenilles, an attachment to the wheels similar to that used for the Tanks in the Great War. Henri Leprince's car had a caterpillar wheel which would take it anywhere over Saharan sands, would carry merchandise and transact business at a speed that the swiftest camel could not hope to attain. Henri was prepared to undertake any employment that was honest; and this last commission, given by Gaston Jambonne, to cross two thousand miles of desert to Timbuctoo, promised to be the climax of his fortunes.

Henri had decreed that Tony Mase should be his companion on this adventurous voyage to the heart of the Sahara. Henri's and Tony's mothers were sisters.

Tony Mase's father had been an officer in the British Army, and in the Retreat from Mons, during the Great War, had been hidden from pursuing Uhlans by a brave Frenchwoman whom he afterwards married. When peace was signed they had settled in England, where their son Anthony was born. Tony in due course was sent to an English Public School; but war wounds early robbed him of his father, and his mother had a hard struggle to give her boy a fitting education. So early in his teens Tony Mase and his mother had joined their French relatives at Algiers, as there were no near relatives of his father left in England.

"Hahaha! it is a great secret, this voyage across the Sahara," declared Gaston Jambonne, watching the cousins narrowly. "We will startle the commercial world in Algiers. We will see our goods delivered in Timbuctoo in record time. It takes six months by ordinary pack camel to complete the journey to the Heart of the Sahara, but your wonderful little car, mon brave, will do the trick in eighteen days. Hahaha!"

"Eighteen days from Touggourt!" put in Tony Mase, naming the town that was on the edge of the desert, where the Crimson Caterpillar would start her journey after being unloaded from the train. "Eighteen days from Touggourt, Monsieur Jambonne?"

"Hahaha! Yes-yes," agreed the Algerian with his customary gurgles, shooting a glance at the English boy whose persistent gaze he seemed to resent. "Certainly I mean eighteen days from Touggourt. Have I not been liberal with you, Henri my brave one, and have I not promised similar liberality on your return from Timbuctoo?"

Henri Leprince nodded gratefully at his employer's appeal, the French youth turned to his cousin. "To-day the generous Monsieur Gaston has paid into my bank account the equivalent of one hundred pounds of your English money, Tony, and he has promised another hundred pounds to be paid over immediately on our return."

"But what if we are killed?" Tony addressed his query to the trader.

Jambonne laughed loudly as if it were a huge joke.

"Hahaha! Are you the sort of fellows that get killed? No, no, my so brave heroes; you will conquer all difficulties; for I have my agents to assist you in every oasis of the Sahara, and they, knowing the power of the House Jambonne, will bend every effort to further your journey, and to guard you from all dangers of the Desert—from thirst and starvation, from wild animals and fierce winds, from marauding bands of Tuaregs, from all robbers and—"

"But even your swiftest mehari could not keep pace with our car, Monsieur Jambonne," Tony interpolated. "Your camel rider would be left far behind three minutes after the Crimson Caterpillar had got going."

"Hahaha! It will surprise you, English boy, the efficiency of the House Jambonne. And unless your so wonderful Crimson Caterpillar should blow up and go skywards in little bits—"

"Trust ma chère Crimson Caterpillar to win through, monsieur," interrupted Henri icily. Any aspersions on his beloved bus were regarded as a personal insult to himself.

Jambonne was all love and compliments forthwith. "I but suggested the wildly impossible, mon ami, even as our little English hero did when he hinted that the House Jambonne could not protect its agents against the happenings of the desert. Hahaha!"

"We will be back in Algiers by March the Sixth as I have promised, Monsieur Jambonne," asserted Henri Leprince, tapping his chest with a confident Gallic gesture.

"I do not doubt it, my trebly brave hero," the Algerian half-caste responded. "Hahaha! what an epic journey lies ahead of you! And how my friend and agent in Timbuctoo, Sidi ben Baar, will marvel at the swift delivery of the salt bars. Ha! what was that? Is there a listener—an eavesdropper?"

The factor sprung from his chair, pulled open a drawer, snatched forth a revolver and pointed it in the direction of the slight rustling that Tony could only just detect.

The room was half office, half reception room, high up in Jambonne's private house in the Arab quarter. There was only one window looking out over the port of Algiers, and that was a grille of iron bars rather than a window of glass. The iron-studded door had clanged-to behind the youths as the giant Kabyle porter had retired. There was one big table, at which the Algerian sat, and a divan on which he might recline. Rows of ledgers stood on shelves to right and left, and a series of pigeon-holes filled with papers occupied the wall behind him. Two wicker chairs, on which the cousins sat, completed the furniture of the office. It looked impossible for anyone to hide there.

But Jambonne had knelt and pulled upward the draping of the divan.

"There certainly came to my ears the movements of a spy," said Jambonne, as he let the hangings of the divan drop over the vacant space revealed. "Ha! I have it. There is someone boring a hole in the wall through which they may hear our secrets. Ha!"

There was a sound of something scratching or disturbing papers in one of the pigeon-holes behind Jambonne's seat.

"I have you, foul eavesdropper," cried the Algerian as he flung himself against the nest of small compartments, and from one of them tore paper after paper frantically with one hand, whilst with the other he menaced the tiny hole.

Tony was curling his lips at the half-caste's frenzied fear; Henri was puzzled at his employer's sudden onslaught on the pigeon-hole.

"Do not move," Jambonne cried. "I have you covered. I see your eye—it glistens. My bullet will pierce your brain, you double-dyed villain."

A mouse sprung to the floor, and Jambonne collapsed on to his chair.

"Hahaha! How did you like my acting?" asked Jambonne, slipping his revolver swiftly back into the drawer. "Hahaha!"

But Tony Mase knew it had not been acting and wondered at the fear the factor showed over such a small matter as a trading journey.

"Hahaha! Henri my brave boy," continued the Algerian, wiping sweat from his brow with a red silk handkerchief. "It is thus I impress my agents with the urgency of the work they undertake for me. You dear boys, so generous, do not guess how my competitors seek to wrest my trade secrets from me. And it may be that they will place another car to compete with me on this journey across the Sahara."

"There is no second Crimson Caterpillar in North Africa," declared Henri proudly.

"That is why I engaged you, Monsieur Henri Leprince. Hahaha! Yet be as secretive as moles, as silent as serpents, as impenetrable as marble, for, believe me, the future of a colonial empire—of commerce, may rest on your young shoulders!"

"Vive la France!" cried Henri, solemnly saluting.

But Tony bent to do up his boot-lace. He didn't relish heroics and wasn't at all sure that he trusted Monsieur Gaston Jambonne.

The factor, following the mouse incident, recovered his composure with a perfect tornado of laughter, then produced a document for Henri to sign.

It was merely a legal agreement between Gaston Jambonne and Henri Leprince, drawn up in the roundabout long-winded way beloved by lawyers of all races, stating that a consignment of salt bars should be duly delivered by the said Henri Leprince for the aforesaid Gaston Jambonne to Sidi ben Baar in Timbuctoo, and if the aforesaid Sidi ben Baar desired to be delivered to the aforesaid Gaston Jambonne certain goods to be carried by the aforesaid Henri Leprince on the return journey, the said goods must be delivered on or before March the Sixth following. In return for which service, shorn of all its legal verbiage, the document stated that Henri should receive the equivalent of one hundred pounds before he started and a second hundred on his return.

The French youth signed without further ado, though Tony whispered that there ought to be some further consideration of the document first.

Jambonne noted the English boy's caution. "Hahaha! A mere formality amongst friends, Leprince my brave one. I know you well enough, Henri, to realise that you would accept my word. You have known me longer than this English boy who is but new to our colony. I do not hesitate to trust my most private affairs to so valiant a hero as Henri Leprince."

The French youth bowed low. "My utmost service is at your disposal, monsieur. We start to-morrow as you have desired, Monsieur Gaston Jambonne."

But unromantic Tony merely raised the query: "Who pays for the petrol, Monsieur Jambonne?"

"Hahaha! The English infant has the trading instincts of his race. Is it not plainly stated in the contract that all expenses of the journey are paid by the House Jambonne? The House Jambonne has resources that the President of the Republic may well envy."

The hero-worshipping Henri murmured: "You are wonderful, monsieur," seeing in Jambonne a king of commerce, a pioneer who would open the undiscovered hinterland of the Black Soudan, and a patron who would place Henri Leprince on the very pinnacle of industrial fame.

"Hahaha! It is indeed a gay and wondrous journey that lies ahead for you two heroes," concluded the Algerian factor, pressing the push of an electric bell. "To-morrow at ten o'clock, I will meet you at the railway station to see your Crimson Caterpillar duly entrained for the midday departure. Hahaha! Hahaha!"

There was a prodigious tap on the iron-studded door, five times repeated.

Jambonne arose and crossed the floor. "The door to my sanctum once shut cannot be opened except from the inside, and the knock you now hear is a signal which is changed each day. So no intruder can disturb my serenity."

"Except a mouse!" Tony Mase could not keep himself from blurting out.

Jambonne shot a glance that was not kind at the English boy, then laughed uproariously. "Hahaha! these English they are droll, my Henri. But we, my brave one, must take responsibility upon our shoulders, and think only of the goal."

The Algerian half-caste pulled back a bolt, turned a handle, and the massive door swung hack to reveal the same giant Kabyle who had conducted the youths into his master's presence.

There was a swift interchange of words in a dialect that neither of the cousins could understand, then, with a tornado of "Hahahas!" behind them, they were led once more down the stairs by the black Kabyle.

"A great adventure!" exclaimed Henri as the cousins passed out into the narrow street where scarcely a ray of sunshine could penetrate.

"A great venture!" said Tony Mase.

For whilst the French youth was brimming over with confidence, the English boy, remembering the unsmiling eyes of Gaston Jambonne, was not so sure that everything was as straightforward as the Algerian factor would have the cousins believe.


CHAPTER II
THE MAN WITH THE CROOKED NOSE

"ALREADY we are shadowed, Henri," remarked Tony Mase, kneeling to fumble with his boot-lace and to cast a sidelong glance at a tall figure in an Arab burnous who was following in their wake.

"The wonderful Jambonne has deputed a servant to see that we reach our house in safety, Tony, suspicious one," responded the jubilant Henri who was busy building commercial castles-in-the-air of which Gaston Jambonne was the architect.

The cousins had parted from the Algerian factor only a few minutes before. It was the watchful Tony who had spied the tall figure in the shadowed doorway opposite Jambonne's residence. An Arab he seemed; but Tony could not see his face, the burnous cloaked the stranger from head to foot. But he was following them—Tony was certain.

Night was falling swiftly, and the crowd grew in numbers as the steep streets of the upper town were left behind, and the boulevards of the town of Algiers were neared.

"Take this short cut, Tony," advised Henri. "You will see that your fancied spy will not follow us."

The cousins dived into a narrow alley, so narrow that when pack mules passed, the youths were forced to press back against whitewashed walls or iron-studded doors with over-hung casements above.

Came sudden cries of alarm, shouts of warning, and screams of pain.

A bolting, bucking, biting mule sent the Algerian crowd fleeing for safety up the narrow alley. And the mule followed.

Tony and Henri were borne backward by the press of scared natives. A Moor with a broken leg was dragged backwards by two black servants. An unfortunate little bootblack was lifted high in air by the mule's rear hoofs, and the little fellow fell on the cobbles a motionless bundle of rags.

Tony would have pressed to the rescue, but he was jammed by the crowd about him.

"Tackle the beast, somebody," he shouted.

His shout was answered by no other than the hooded man who had shadowed the cousins. "Well spoken, boy. Better a dead mule than a crippled shoeblack."

The mysterious man's massive shoulders had forced a way through the crowd till he faced the bucking mule with a knobbed stick.

Raising his weapon aloft with two hands, the hooded stranger with incredible celerity brought it down with a thud between the mule's ears.

The biting mule stood swaying on its four feet, all the fight taken out of it. Wider and wider straddled the four legs.

Tony laughed aloud at the grotesque appearance of the animal. "That blow has made the mule a perfect ass," he said.

But Henri was too enthused at the shrewd blow of the stranger to heed his cousin's joke. "Bravo, gallant rescuer," he said, clapping the hooded stranger on the back. "You have saved all our lives."

But the man of the knobbed stick had bent to lift the little bootblack.

A skinny old Jew ran up, demanding compensation for his injured mule. Whereupon the crowd turned their attention to the owner of the mule which had caused all the trouble.

A black soldier clapped a great hand about the skinny neck of the Jew, and propelled the protesting Israelite down the alley with forceful knees.

The crowd, forgetting their rescuer, followed the soldier, demanding satisfaction of the Jew who set savage mules on innocent Algerians.

"Ungrateful canaille!" remarked Henri, then turned to the hooded man who was bearing the injured bootblack in his arms. "How can we thank you for your heroism?"

"I seek no publicity," said the stranger speaking in French, as he had done throughout the incident. "But at the midnight hour, Henri Leprince, I will come to the red rose bower in your garden. Fail me not, there is more in this than your wildest imaginings."

Suddenly under overhanging casements a door opened and a light shone forth. The lantern dipped twice and was shrouded.

"Au 'voir!" whispered the hooded stranger. And, bearing the injured cireur in his arms, he disappeared into the shadows.

There came the clanging of a door, and only a stupefied mule remained to prove the prowess of the mystery man who had faded from sight.

"By the Tower Eiffel!" exclaimed Henri. "Who is that magician who knows the red rose bower hidden in the depths of our walled garden? I wonder if he really is in the employ of Monsieur Jambonne. I should like to have seen his face."

"I saw it," said Tony triumphantly. "When he lifted his stick to fell the mule, his hood fell aside. The face was the face of a white man. And certainly I should recognise it again, for our rescuer's nose was a crooked one."

"The man with the crooked nose—we meet him at midnight!" cried Henri, striking a dramatic pose.

"Wait and see!" said Tony, who was always so practical that he annoyed his imaginative cousin.

At the rose bower in the garden of the Leprinces the two cousins awaited the man with the crooked nose.

"If the man who followed us and rescued us from the hoofs of the mule is not a spy of Monsieur Jambonne," said Henri, "maybe he is a trade rival who would worm the secret of our desert journey out of us."

"At least he is no Jew trader," Tony responded. "His face was that of a Frenchman."

"Why not that of an Englishman, Tony?"

"No, Henri, he was no Englishman. His features were too—refined," retorted Tony, anxious to say the right word that wouldn't offend his French cousin, though "refined" didn't exactly express his British prejudice.

The cousins constantly argued as to which was the finest race. Henri Leprince asserted that the British were superior fellows—for politeness' sake! Tony as stoutly maintained that the French were by far the most gallant nation—though the word "gallant" had a restricted meaning to Tony if truth be told. Both asserted loudly that his cousin's countrymen were the noblest, and both were quietly convinced in their own hearts that no nation surpassed his own.

So, whilst awaiting the arrival of the mysterious stranger who had dogged their steps, the cousins launched into the ever-recurring topic. And no stranger with a crooked nose came to stay their argument.

The eastern horizon was greying with the coming of morn when the cousins gave up their vigil.

"It was foolish to heed the word of a stranger; his words may be as crooked as his nose," Henri said.

"He spoke like a true man," asserted Tony. "I trust no ill has come to him. I feel, somehow, that we shall see him again."

At 10 a.m. the cousins met Gaston Jambonne and his giant Kabyle at the Goods Department of the Algiers railway station, as had been arranged.

"Isn't she a beauty?" exclaimed Henri as he and Tony hasted into the yard where the Crimson Caterpillar rested by the truck on which she was shortly to be hoisted.

The Crimson Caterpillar was a compact little car, a Citroën of the 10 h.p. type, with two seats for chauffeur and companion. The rear of the car was fitted with a considerable rumble, leaving ample space for merchandise. But the unique feature that made Henri's car capable of crossing the desert was her chenilles or "caterpillars."

These ingenious contrivances consisted, in principle, of an endless rubber band, a sort of supple moving rail which unrolled as the car proceeded over sand; thus, as it were, laying down her own railway track and picking it up again behind her. There were modifications in her structure that might have puzzled a novice till he was reminded that it was vastly important to protect the Crimson Caterpillar from sand which might invade her bearings. In her construction the consumption of water had been reduced to a minimum by adding condensers and sheaves of lateral wings on the radiators. She was well-named the Crimson Caterpillar, for Henri had ordered her bonnet to be a bright crimson, and everywhere the enamel published part of her name whilst the chenilles published the rest.

"Hahaha!" roared Jambonne waddling up to Henri. "We have already loaded the salt bars." And he pointed to his giant porter.

The Kabyle grinned like one guarding a great secret.

"Listen to me, my hero Henri," continued the Algerian factor. "I desire you to tell my friend Sidi ben Baar when you arrive in Timbuctoo that this—" he pointed to a block of salt at the base of the pile packed in the rumble—"is the best bar—the best bar, mark you, Henri, the Best Bar! Sidi ben Baar always retains the best bar for his own consumption, and I have marked it with a crescent so!"

The Algerian pointed out the sign scratched with a dagger on the soft surface of the bar of salt. Beyond noting their employer's instruction, the youths took little notice of that crude mark on which the whole success or failure of their desert venture was to depend!

"Sidi ben Baar shall be shown the crescent sign, Monsieur Jambonne," declared the conscientious Henri.

"Good! Now, for a space, I go," said Jambonne hurriedly, as he and the Kabyle swiftly passed behind a nearby shed.

The Customs officials were coming.

The official was friendly with Henri and was aware of the business rectitude of the young Frenchman. "This is indeed your car, Leprince?" he asked. "It is not the car of Gaston Jambonne?"

"The Crimson Caterpillar is my very own property, sir," replied Henri. He was going on to say that, though employed by Jambonne, the factor had no share in the car's ownership.

"Your cargo is—?" came the query sharply.

"—is but salt, monsieur," Henri replied.

"And you are sure you carry nought but salt? No smuggled goods, such as firearms?"

"Nothing but salt, sir," declared Henri. "See! there is every inch already occupied with salt and such provisions of food and oil as will be necessary to carry us to Timbuctoo."

The official came close to Henri. "We do not trust a certain Gaston Jambonne. But you are a true Frenchman, and your salt may be passed." Wherewith the official scratched certain chalk marks on the tarpaulin which was forthwith flung over the Crimson Caterpillar by the Customs officers.

"The preliminaries of our enterprise are successfully accomplished, Tony," declared Henri. "The Crimson Caterpillar will be hoisted to the railway truck, and the car will not be touched again till Touggourt is reached. And then it will mean little more than lowering ma chère Caterpillar to the desert sand. In fact the consignment of salt will not be touched till it is unladened by Sidi ben Baar in Timbuctoo."

So thought Henri Leprince, having no foreknowledge of the existence of a certain strange boy called Aa!

"Anyhow it's time we got back to lunch," said Tony, consulting his wrist-watch.

But as they summoned a taxi to take them home for the final farewell, the Customs officials having disappeared, Gaston Jambonne and his giant Kabyle reappeared.

The trader would leave nothing to chance. The Kabyle would remain in the vicinity of the Crimson Caterpillar till it went south by the Biskra express which the cousins were joining at midday.

"I can't understand all this fuss about a few bars of salt," said Tony to Henri as they were borne home to lunch.

Henri smiled in a superior manner. "Salt, my ignorant English cousin, is as valuable as silver in the distant deserts. Without constant supplies of salt Timbuctoo, an ancient city as old as Time, now the capital of our Saharan empire, could have existed but a few years. Twice a year the Azalayi for centuries past has set out from Timbuctoo, under military escort, to fetch some two or three thousand bars of the precious commodity from the salt mines of Taoudenit. All Timbuctoo turns out in festive fashion to greet the returning Salt Caravan with thrum of tom-tom, blare of trumpet and the huzzas of twenty differing tongues—so important to the life of the desert metropolis is the Azalayi. . . . Jambonne says that our little consignment arriving just before the ordinary supplies come in, will mean much money for Sidi ben Baar and much profit to himself."

"And what merchandise are you to bring back, Henri?" the cautious English boy asked.

"My benefactor did not say, for he did not know. Sidi ben Baar might desire us to bring back costly carpets, rare feathers, ivory or gold dust."

The taxi-cab was passing through the Mustapha suburb of Algiers at the moment. Tony sprang to his feet.

"Look!" he cried. "I saw the man's face."

A car was drawn up before a private residence perched high above a flight of steps. A man in Arab burnous had been lifted out, and was being borne on a stretcher through the iron gates at the foot of the stone stairs.

"Who is it?" cried Henri as he signalled the taxi driver to stop.

"The Frenchman with the crooked nose," cried Tony. "Now we know why he didn't keep his appointment at the rose bower."

"Foul play!" exclaimed Henri springing from the cab.

But the car that had brought the wounded man to the gates whisked off in a cloud of dust. And the stretcher passed through gates that clanged-to behind it.

A villainous porter glared at the clamouring cousins.

"Whose house is this, garçon?" Henri demanded through the bars of the gates.

"What business is that of yours?" was the retort. "May not a doctor keep a private hospital without a passer-by wanting to inspect his patients! Indeed, youths have been known to come into danger from this evil habit of curiosity."

The man's manner was menacing.

"But I demand to see your master," cried Henri.

"He cannot come. He is operating on a patient—cutting out his liver," responded the man with an evil grin. "Such is the only cure for curiosity."

Tony was consulting his watch. "Our train leaves in less than an hour," he urged. "And we have yet to lunch and say our farewells."

"But yes," responded Henri, jumping again into the taxi-cab, "we must not desert our Crimson Caterpillar. Though we leave an unsolved mystery behind us, Tony."


CHAPTER III
THE GATEWAY TO THE DESERT

"SOON we reach. Touggourt, mon brave," Henri remarked as the train bearing the cousins and the Crimson Caterpillar neared the end of the journey to railhead. "Before us the illimitable Sahara!"

Tony grinned at the outstretched palms of his cousin. "My dear Henri, the desert ahead is but a mere three and a half million square miles, so you mustn't say it hasn't limits."

"Oh! you prosaic English, you have no poetry," retorted the Frenchman. "But certainly it is a desert big enough to conceal its boundaries, big enough for a regiment to lie down and die in."

"But the Crimson Caterpillar is not the sort of creature to lie down and die in the desert, is she?" chaffed Tony.

"Trust ma chère Caterpillar to win through," said Henri solemnly, his good-humour restored.

"I wish we could have followed up the mystery of the man with the crooked nose," Tony continued, remembering the incident outside the villa in Algiers. "Was he friend or rival? Why should he visit you secretly? And how did he receive his injuries? And whose was the house he was carried into?"

"The Villa Agadaas was the name painted on the gates, thou unobservant one. And I have left the affair in the hands of my father, who has promised to send a wire to the post bureau in Touggourt. He will put the matter in the hands of the police, if enquiries are not satisfactory."

"Anyhow, he will have had time to investigate," said Tony wearily; "it seems years since we left Algiers."

Though much interesting time had been spent studying maps and the prospective route across the desert to the exclusion of all other topics, the cousins' thoughts came back to the alarming affair of the man with the crooked nose, and they were anxious to learn what news awaited them from Monsieur Leprince, senior. According to schedule, they were to spend an afternoon and a night at Touggourt before bidding adieu to civilisation.

As the train steamed into the station where they were to alight, they looked forth on fair prospects of verdure bordered by sand.

"An emerald set in gold," cried Henri fantastically.

"A diving board whence we plunge to a sticky death," corrected Tony, who was wont to damp down his cousin's Gallic exuberance.

"Pah! you illogical fellow, did you not say but an hour ago that ma chère Caterpillar was not the creature to lie down and die in the desert? Certainly we shall win through."

Their first care on disembarking was to see their car safely shunted to a siding. Following which an adjournment to the Hotel Djouf was to be made. Gaston Jambonne had arranged for the youths' reception there. Such was the scheme outlined by Henri as the cousins descended from the train.

Their feet had scarcely touched ground before they were the centre of a clamouring, hustling crowd of touts and interpreters of all shades of colour, jabbering in the tongues of Babel.

"I Tommy-Tom, quite English," announced a coal black Makhazni from the interior, concentrating his attention on Tony. "I spik same you, oh yes."

Meantime an ancient Moor was informing Henri that he—the Moor—was three-quarters French and could speak the language of Paris.

"This is more than a joke," cried Tony, Jerking his knee into a too-adjacent body, the fingers whereof were seeking to find his purse.

The pickpocket doubled up and backed. Only to be replaced by other rogues in that sea of coloured humanity.

"Gendarme!" cried Henri from out his encircling pests.

But no policeman put in an appearance.

Tony yelled to two Zouaves to come to the rescue, when all at once, there was a miraculous change in the situation.

An Arab leaning on a crutch limped forward, said a few words on the outskirts of the scrimmage, and the crowd melted like snow before a solution of salt. So that the cousins found themselves facing one lone cripple.

"Gaston Jambonne bade me take you to the Hotel Djouf," said the miracle worker in the lingua franca of the Sahara. "I am your obedient servant."

"What are your fees?" demanded practical Tony.

"I am already paid," said the crippled Arab proudly. "I am of the House Jambonne."

The Arab stumped ahead of the cousins, and although touts of every degree of rascality bore down on the visitors, at a sign from the cripple they instantly withdrew.

"Your car is guarded," said Jambonne's agent when Henri would have turned to inspect the Crimson Caterpillar. "You can see her when you have dined."

It was a strange city there on the outskirts of civilisation. From Moorish cafés came the shrill squeaks of reed pipes, the tireless tattoo of tom-toms, the ceaseless jingle of tambourines. On curious stalls traders exhibited the trophies of the desert for sale, whilst quite modern emporiums showed European products behind plate glass.

Passing the cousins on the side walk were weird figures from out the desert world, natives to whom as yet Tony could attach no name. There were stately sheiks wearing robes fashionable in Father Abraham's time, there were colonial lieutenants flaunting gay uniforms that would be the vogue on the Bois de Boulogne a year hence. Everywhere there were bright patches of colour, the garish dress of Spahi, Turco and Zouave.

Tired from their journey the travellers were glad to see the sign "Hotel Djouf."

"What a glorious array!" cried Henri as they passed a great clump of blooms amidst a beautiful background of flowering shrubs and feathery ferns within the hotel grounds.

"But there's a queer ornament in the garden," Tony exclaimed, pointing to a cowled figure squatting like a statue amidst the flowers.

"Probably a marabout or saint of sorts," remarked Henri carelessly.

Tony, however, noted that the cowled head turned slowly as they passed, and the English boy felt sure that piercing eyes were following their every movement with more than necessary interest.

The cripple led the cousins to a stalwart Soudanese hall porter. "A servant of the House Jambonne," he whispered.

The Soudanese porter became their devoted slave. The cripple seated himself at the door of the hotel.

After a meal amidst diners not one of whom was white, the cousins set out, under the guidance of the crippled Arab, for the post bureau to see if messages awaited them there.

There was a telegram from Henri's father.

Henri's brow knit as he read. "The Villa Agadaas was deserted when my father visited it," he told Tony, "and the house agents whom he saw later assert that the Villa has had no tenant for six months. The visitors left no clue, and the police pooh-pooh my father's information."

There was another telegram—from Gaston Jambonne. "Depart at dawn—secretly."

The cripple assured Henri that the Crimson Caterpillar was guarded by the agents of the House Jambonne, but Henri could not rest till he had inspected the car which had been unladen from the railway truck and was ready for an early start. A motor mechanic was polishing the crimson bonnet when the French youth arrived.

"Ma chère Caterpillar, at any rate, is ready to comply with our employer's orders," Henri declared, "but I wonder why Jambonne sends this telegram. What new development has made necessary this sudden departure that he commands?"

"There's more in this than meets the eye, as the pugilist said of the blow that knocked him out," remarked Tony. The English boy, though he jested, left nothing to chance; he was curious about the cowled figure that sat In the hotel garden.

"He is a holy marabout from the desert," the Soudanese porter told Tony. "There he has sat for ten days, living on such fare as the hotel flings to the dogs. He does not even solicit alms nor chant passages from the Koran."

As he looked from his bedroom before retiring, Tony saw the marabout still sitting there.

He was determined to probe the mystery, not leave enquiries till too late, as in the affair of the Villa Agadaas.

He slipped out into the garden without Henri's knowledge. He passed close to the cowled figure.

There came a softly spoken question in a tongue Tony did not understand.

"Do you want word with me, holy man?" Tony asked in French.

In broken French came the response. "What do you carry to the city of Timbuctoo?"

"My cousin and I are taking bars of salt, holy man."

"Take you the salt to Sidi ben Baar?" came the query that made Tony grow cautious.

"Why ask that, holy man?"

"Is there nought but salt in thy car?" the marabout asked, and as he leaned anxiously forward, the cowl parted to reveal—a weird white face and curious yellow eyes that gleamed like a cat's.

"I swear we carry nothing but salt, holy man," Tony found himself saying in answer to compelling yellow eyes. "Good night."

"Au revoir!" said the marabout as he drew his cowl about his strange whitish-grey face with the catlike eyes.

Tony quickly found his cousin and told him of the strange interview amongst the flowers of the garden.

"I will speak with the mystery man myself," Henri said.

But when they came to the place where the marabout had sat, the man had completely disappeared, and only the wail of some reed instrument came weirdly to their ears from the verge of the desert.


CHAPTER IV
UNEXPECTED WELCOME TO OUARGLA

IT was early morning when the cousins, following Jambonne's telegraphed instructions, set out from the Hotel Djouf. The proprietor had refused all payment: was he not the servant of the House Jambonne?

The crippled Arab was awaiting them, and bore them company.

"That marabout who sat amongst the flowers—who was he?" Tony asked the Arab.

But the cripple evidently knew nothing certain of the mysterious man who had disappeared; it would seem that the marabout, at least, was not of the House Jambonne. "He was a Tuareg—one of the Veiled Ones," was the only information that their Arab companion could give.

"The Veiled Ones—who are they?" Tony asked Henri.

"The Veiled People, as the Tuaregs are known throughout the Sahara, are the aristocracy of the Desert," Henri explained. "They are of a southern race of Berbers, and, what is a curious fact for an African race, they are white men—almost."

"Our marabout of the flower bed was whiter than a white man," Tony declared, "his face was as white as a bladder of lard. Perhaps he was a leper."

Henri gave a gesture of dissent. "The Tuareg is white and proud of his colour; he is a warrior, and his Berber ancestors twice invaded Europe in the early days of history. He dwells away in the wild mountain fastnesses of the Sahara, whence he is wont to come forth to raid and kill. For the Tuaregs are fighters by heredity and training, though our French Colonial administration is bringing them into something like submission. No, Tony, your Tuareg marabout is not a leper."

"I wish you could have seen his face, though I didn't see much, certainly. He wore a sort of veil almost to his eyes—I suppose that is why the Tuaregs get the name of Veiled Ones?"

"Yes," agreed Henri. "But now let's think of our Crimson Caterpillar and the epic journey before her."

"Humph!" growled Tony, "it seems to me that the Crimson Caterpillar leaves a mystery behind her wherever she goes—the wounded man with the crooked nose in Algiers, the sickly white marabout in Touggourt. I wonder what mystery awaits in Ouargla?"

"Always there is mystery in the desert, Tony, but we travel faster than mystery can follow," laughed the French youth.

"Don't know about that!" retorted the English boy. "Anyhow we can't travel faster than wireless."

Yet, curiously enough, an hour after the Crimson Caterpillar had faded into the blue immensity of the sand plains, came a wireless telegram to Touggourt for Henri Leprince. "Await me at Touggourt," said the message. "Of incredible importance. He of the Rose Arbour."

But by that time the Crimson Caterpillar had left the last Kouba, or Moslem tomb, of the Touggourt district far behind, and was proving the unique value of her "caterpillars" on the sebkra, the dried-up sea of aeons ago. Instead of getting sand-bogged every few minutes, as rubber tyres would have done, the Crimson Caterpillar's wheels raced steadily onward.

She did not need her back wheels cleared from sand, did not require spades and jacks and levers to raise her from pits of her own making, nor camels and mules and a crowd of hauling natives to drag her to firm ground, nor sacks nor boards nor fine wire netting for her front wheels to pass over.

"No no," boasted a proud owner. "Ma chère Caterpillar is no ordinary car, my Tony, she sees the sand, heaps it up in front of her, then planes it down and rolls along leaving her path behind her."

Only once in the first day was there any difficulty with the unique car. In the sand dunes of Temassine, where giant drifts of drinn grew, a pulley got stuck and fouled the caterpillar. Tony and Henri, however, soon put that to rights, and by evening the Crimson Caterpillar came in sight of the place where Henri planned to spend the night—Ouargla.

The slender minarets of the mosque showed above the battlements of the fort where France kept watch over her desert territory.

Soon the motorists were aware that their car had been seen, for a posse of horsemen under a French lieutenant issued from the fort and galloped towards the travellers.

The gallant Lieutenant addressed himself to Henri. "We give you welcome, Leprince, to the Golden Key of the Desert. We beg to be allowed to entertain so enterprising a couple of voyagers. With us we bear two steeds brought for your use. You will take the place of their riders who are skilled motor mechanics. These two may be trusted to take care of your car whilst you yourselves disport yourselves in our papote."

Henri stared at Tony. Tony stared at Henri. They would have liked a private conference: Gaston Jambonne had said they were to travel secretly, but here at the onset of their enterprise they were being given a military reception; here, in Ouargla, a town Henri had never visited, the young Frenchman's name was known and their arrival anticipated.

Henri stepped from the driving wheel to the sand. Bowing to the lieutenant, he said: "It is remarkable that you are aware of our coming, monsieur."

"Always in the desert it behoves us exiles to have as many eyes as a peacock, each eye glued to a field-glass, mon ami. On the morrow, all being well, you and the English boy shall continue your pilgrimage."

"Why should not all be well, monsieur le lieutenant?" Henri demanded with some heat.

The lieutenant shrugged his shoulders in reply. The two mechanics bounded into the seats vacated by the motorists. Two privates, holding the riderless horses, bade Henri and Tony mount, with eloquent gestures.

"Monsieur le lieutenant, never shall I forgive your mechanics if they hurt one rivet of ma chère Crimson Caterpillar," Henri exclaimed.

"They are experts, Leprince," said the officer tersely. "I beg you, if you can ride, to mount your horses forthwith."

Reluctantly Henri, with a rueful glance at his car, sprang to the saddle. Tony, urged by the insinuation that he might not be able to ride, was astride his horse quicker than his cousin.

Towards the battlements the cavalcade trotted, Tony wondering what the papote where they were to be entertained might be like.

Through the palm groves, headed by the lieutenant, the posse of horsemen passed; everywhere there were date palms and abundant water, for the underground river of the Wadi Mya has made Ouargla a place of fertility and importance through the centuries.

The Crimson Caterpillar followed in their rear; but after they had passed into the fort of Ouargla, Tony noticed that the car went in another direction—"to the garage in the town," as the lieutenant explained to an anxious Henri.

The papote proved to be the sergeants' mess, where gathered the non-commissioned officers of a detachment of France's Foreign Legion. It was a strange assortment of soldiers, one sergeant had been a Russian nobleman of Moscow, another sergeant had been an Italian ice-cream seller at Margate, a third officer was a Pole who cheerfully confessed to murder in Munich, a fourth was said to be an Englishman—a silent gentle flaxen giant with blue eyes.

The non-commissioned officers dressed for dinner in white blouses which were belted loosely over baggy, white corduroy breeches. Each sous-officier, apparently, could speak not less than four languages, but the conversation during dinner was mostly in French. Tony was surprised to find how elegant were their manners and how excellent was the meal. Indeed the sous-officiers of the Legion were no less refined than the lieutenant who had ridden forth to greet the motorists.

It was after dinner when Henri grew fidgety. "I must wish ma chère Caterpillar good repose," he said to Tony, and begged the Russian sergeant to conduct them to the garage where the Crimson Caterpillar was housed.

The Russian, however, though vastly polite, made no move to accede to the French youth's request. The Italian, with many elegant gestures, declared he feared the rigours of the Saharan night. The Pole apologised but ventured to think such a visit impractical, and, on being pressed, insisted it was against orders. The corporal of the blue eyes and flaxen hair, turning to Tony, said in English: "Don't take risks, my lad. It is best for you both that you do not see your Crimson Caterpillar to-night."

Henri heard, shrugged his shoulders and made his plans. So they sat talking of the wonders of the desert wastes, of star-spangled skies, and of rose-red dawns, and of pitiless raiders and the unknown lairs where the Veiled Ones hid.

"Beneath the desert sand an older civilisation lies buried," declared the Russian as he smoked cigarette after cigarette of yellow-hued paper and pungent aroma. "Once there were fertile lands where rivers flowed and beautiful lagoons gave life to groves of date palms and luscious tropical fruit; there were cities of wondrous beauty where dwelt a race now conquered by the invading sand."

"There is much treasure deep—deep down under centuries of sand," said the Pole, sucking at his pipe.

"Dig down a mile," said the corporal of blue eyes in Tony's ear, "and you'll find—you're tired!"

"But are there really buried cities beneath the sand?" Tony asked of the English-speaking corporal.

"Haven't a doubt of it," responded the handsome young giant, "but I wouldn't finance an expedition to dig 'em out—even if I had the money. Don't trust the Sahara, my lad, she'll swallow you and ask for more. The English have done well to keep away from her. Good night." And the corporal who wouldn't confess to a nationality or a name passed out of the mess-room, and out of Tony's life.

Shortly afterwards the two cousins were shown to their quarters—a barrack-like apartment with two camp beds.

They were left alone.

Henri examined the fastenings of a prison-like window. "Ma chère Caterpillar will not sleep without my good-night kiss," he said with a wink. Following which Gallic sentiment, Henri set about climbing through the window aperture.

Tony followed stealthily, whilst outside their bedroom door a private of the Legion kept watch.

With the utmost caution they crept towards the barrack gates.

Nearing a sleepy sentry who had received no orders regarding the visitors (the guard at the bedroom door was considered sufficient by those in authority), a bold Henri, and a no less confident Tony, saluted the black sentry, and left him gaping whilst they passed out into the night.

A lean native, nigh naked, rose up out of the shadows. "Of the House Jambonne," he whispered. "Whither shall I lead you?"

"To my car," was Henri's terse reply.

The lean native instantly loped off at such a pace that the two adventurers had all they could do to follow.

By narrow lanes, in the shadow of long, low buildings whence came the hum of voices, the trio passed to another part of the fortified town.

"Thy Crimson Caterpillar is there," said the lean one, pointing to a zinc-roofed shed. "And if I do not see you again, tell Monsieur Jambonne that Yussuf of Ouargla serves him faithfully." And the man disappeared as suddenly as he had arrived.

Before the cousins was a workshop whence flared kerosene lights, and through the open doorway could be seen privates of the Legion busy about the Crimson Caterpillar.

"We'll surprise them," said Henri indignantly. "They appear to be tampering with our goods."

At the words the furious French youth burst into the shed, brushing aside a bayonet that would have barred his entry.

Tony followed, giving the truculent sentry a punch—below the belt, I fear, for the man gasped.

The cousins were astounded to see the rumble of the Crimson Caterpillar emptied of salt bars and stores, whilst superintending the removal was the lieutenant, who, instead of asking the cousins to dine with him, had put them in charge of the sergeants' mess.

"What does this mean?" Henri demanded, striding up to the lieutenant.

The officer smiled, raised his sword in salute, and bowed low, replying with a smile: "A mere matter of custom."

"This is beyond a joke, sir," Henri cried. "Our goods duly passed the Customs officials at Algiers and the official said I need fear no further interference with my goods. Was not the Customs permit chalked on the tarpaulin?"

The lieutenant bowed again and said nothing.

"Why did you take my salt from the rumble, monsieur lieutenant?"

"To put it back again," responded the lieutenant blandly.

Nor could the cousins gain further information than that.

Henri would not move from the shed till he had seen every bar of salt replaced in the rumble, taking care that "the best bar" with the scratched crescent upon it, should take up the identical position at the base of the consignment, as Gaston Jambonne had decreed.

The cousins returned to their quarters under the guidance of a French private, but in the offing Tony caught sight of the agent of Gaston Jambonne who had brought them to the spot.

On the morrow the Crimson Caterpillar was bound to be in perfect condition, and Henri almost forgave the lieutenant seeing how efficiently the mechanics had cleaned, oiled and adjusted all the bearings. "He thought we were smugglers," explained Henri to his cousin, dismissing the subject, and waving a hearty farewell to the officers who saw them off.

"It is great gratification to find you true sons of France," shouted the lieutenant after them.

So once more the two intrepid motorists set their faces to the forlorn spaces ahead.


CHAPTER V
A NIGHT UNDER THE STARS

THE Crimson Caterpillar had not travelled far from Ouargla when Henri suddenly drew up.

The French youth pointed to a flat hill that dominated the sea of sand. "That is Gara Krima," he said, standing up in the car and saluting. "Thence the pioneers of France set out for the Niger. The Foureau-Lamy mission took two years on that journey, which we plan to accomplish in twenty days. Thus rapidly does Man conquer space and time, my brave one."

"Isn't it nearly lunch time?" was Tony's terse response. His cousin's Gallic sentimentality jarred on his own Saxon reticence; like most men of British blood, Tony grew more silent the more his emotion was stirred. Tony would counter Henri's eloquence with trivialities. Hence: "Isn't it nearly lunch time?"

"No, my cousin of stomach and no soul, we may not yet eat," was Henri's rejoinder. "Here we may study our maps."

The French youth, though prone to rhapsodise, was methodical and left as little to chance as Saharan expeditions permitted. He had maps of every section of his journey to Timbuctoo, and had carefully studied the work of the Citroën Expedition who had first accomplished the conquest of the Sahara by car. Each night of the prospective journey was scheduled to be spent at a particular spot so that Gaston Jambonne could follow his movements readily enough. And the Algerian trader himself had furnished information that was exclusive and proved marvellously accurate.

After leaving Ouargla the Crimson Caterpillar's next night was to be spent in the sand dunes of Kheshaaba, and the journey thither was, on the whole, somewhat monotonous.

"We are adrift on a desolate sea of sand," Henri remarked towards noon, "only the island of Gara Karim remains to direct our passage to the unknown wastes ahead where dangers lurk. It is indeed a sea of desolation wherein our gallant ship may be wrecked."

"Behold in the trough of the sea a shipwrecked mariner!" chaffingly cried Tony pointing to something that showed up like a tent on the monotonous sand plain ahead.

Yet was there no need to inspect that casualty of the desert closely. All was over; there was just a framework of bare bones, great curving ribs and a flat skull that reminded Tony of fossils of prehistoric animals seen at South Kensington Museum. The vultures, the jackals, the beetles and the ants had completed their work. Thirst and relentless heat had wrecked that ship of the desert, and its owner, leaving it to die, had continued his journey on another camel.

Soon Tony was to grow accustomed to such desert sights; indeed he grew almost to welcome them, for the skeletons of the camels indicated that the travellers were following customary routes across the wastes.

In the afternoon a yet more tragic relic came to the English boy's notice.

"See yonder, Henri," he said, handing his cousin his binoculars, "yonder is a stone cross."

Henri drew up and referred to a notebook. "Yes it is the grave of two brave missionaries of the Cross," he said, lifting his sun-helmet reverently. "The padres were massacred by Tuaregs, who have since raised this cross to the good fathers' memory. Everywhere in the desert lie the bones of the martyrs of Saharan progress, of missionaries, of scientists, of soldiers, of naturalists, of pioneers who gave their lives for the good of their Cause."

"I suppose we couldn't be classed as martyrs if we were killed," Tony slyly chaffed. "Dead traders aren't counted martyrs."

"I don't know, Tony," said Henri seriously. "Traders bring benefits to the lands whither they come in fair dealing. I believe that I can pray Le Bon Dieu to bless this our enterprise which brings life in the form of salt to a saltless land."

Yet had Henri Leprince known all, he would never have breathed that sentiment.

Strange and disappointing was their next experience.

"Look! Look!!" cried Henri, pointing through the shifting eddies of red sand stirred by the following wind. "A city of beauty in the wilderness, a very Nirvana in the howling wastes!"

Tony stared through the flickering fight. "The city ahead is not marked on our map? And where are the natives of this beautiful oasis?"

But even as the two cousins tried to focus the scene ahead—the purple palm groves, the shining lakes, the clumps of plantain, the fairy-like huts—it dissolved before their eyes. The purple palms merged in the purple of the horizon, the shining lake sank below the sand, the plantain clumps writhed like snakes and were whirled into nothingness, the huts danced to dissolution.

And only one spindly gum tree remained real in that mirage that had deceived them both.

Maybe it was a similar mirage that had lured a party of desert wayfarers to their doom, for not long after seeing the optical illusion of the mirage, Henri caused the Crimson Caterpillar to swerve in order to avoid something white half buried in the sand.

"Human skeletons," breathed Henri. "Seeking water where there was none, the poor beings, maybe white, maybe black, sank exhausted to the sand. See, one lies gazing at the sky from sightless sockets. And there rest two close together, hand still clasped in hand, brothers or chums perhaps."

"Or cousins," said Tony shuddering.

Henri sighed. "It happened long ago, for not a shred of clothing remains to prove their identity, and the bones are bleached white with sun and wind."

They gazed at the poor relics of humanity, then softly the car purred onward, its occupants silent with solemn thoughts.

The Crimson Caterpillar continued onward till nearly midnight, the way was clear before them and the going easy. But by that time the cousins had reached the limit of human endurance.

The tent was quickly rigged under the stars; it was their first night in the open. Tony found it surprisingly cold; the thermometer registered only 39 degrees Fahrenheit.

"I made fun of the blankets you were bringing, Henri," said Tony as he snuggled down into his hip-hole in the sand. "But it would have been no joke without them."

"If fuel were procurable, we would have made a fire, and been only too glad of it," Henri replied from out the depths of his blanket. "And the fire would have been useful to scare off jackals; though, on the other hand, it might have attracted desert robbers."

Tony grunted but did not continue the conversation, for in two minutes he was asleep, and Henri followed in three minutes with a snore.

An hour later, as the travellers lay there in profound sleep, a turbaned head appeared above the adjacent sand dune. He was black veiled so that only his restless eyes could be seen, and was clothed in a blue robe, carrying a long-shafted spear in one hand, a leather buckler in the other.

Below, in the hollow of the sand dunes, a white camel munched at scanty tufts of drinn.

The warrior grunted and crept nearer the sleepers. The stars shone brightly and showed the Crimson Caterpillar outlined against the sand.

The warrior placed his spear and shield on the ground, and, standing erect, revealed the sword, with its cross-guarded hilt, hanging by his side.

With incredible deftness he drew the double-edged weapon from its sheath and raised it before his litham, or black veil. He advanced with the silent step that only the desert-bred can take.

"El hamdulillah!" he murmured softly. ("All praise to Allah!")

A hyena howled dismally in the distance.

Whilst the Tuareg with the double-edged sword drew momentarily nearer the unconscious cousins.


CHAPTER VI
DESERT MOTORING

TONY MASE, when at his Public School in England, had been a Scout, and, therefore, on first rising and prospecting around their camping place, he promptly found traces of their visitor of the night before.

"Hello! we are shadowed still," he cried to his cousin, showing him the spot where the Tuareg warrior had lain.

The French youth saw less than his Scout cousin; and indeed he felt guilty for not having arranged to keep watch throughout the night in turns, so he put the rosiest complexion on the discovery. "If a visitor came, which I much doubt, he was probably a desert policeman who was looking after our welfare."

"Hump!" growled Tony, stooping low and seeking further signs in the swiftly shifting sand.

A slight wind was obscuring the footmarks, but the Scout was able to follow them to the place where the white camel had munched the drinn.

"The spy had a steed," he explained, pointing to unmistakable signs.

"A meharist," was Henri's verdict. "One of the Saharan goumiers, or native couriers on camels, trained by France to guard the wells or convey messages over immense tracts of uncharted desert on their slim-legged meharis. Once they were caravan robbers; France has converted them into caravan protectors. For see, my Tony, how he came and protected us whilst we slept."

"Bet he came and—bolted!" was Tony's explanation. "He was a mere frightened villager from back of the beyond, and, seeing the Crimson Caterpillar looming up in the moonlight, and hearing you snore, thought he had come on a dragon's lair."

But neither Henri nor Tony had given a correct solution of the Tuareg's visit: the agents of the House Jambonne were not all of the mercantile fraternity!

A breakfast of dried dates, bread and condensed milk with water was taken by the travellers, and then Henri proceeded to make observations and map out the day's run by the aid of compass and rising sun, Tony meantime giving the Crimson Caterpillar her breakfast of petrol and water.

So at length the car sped on her way through the immense sand dimes of Kheshaaba, making for Inifel and its fort, which Henri hoped to reach that night.

Spite of an hour's delay in getting clear of the maze of sand dunes, the cousins came to the Wadi Meya in the course of the afternoon.

It was a great relief to eyes grown sore with gazing at the monotonous, heat-radiating sand to look once again on green vegetation, on great gum-trees and clumps of acacia bushes. The Wadi Meya seemed a most beautiful park after the dreary wastes of the sand dunes. At the wells in the valley the motorists made a halt.

A solitary Tuareg on a white camel rode out from concealment, and without comment proceeded to help them get water from the well. Henri tried to speak with him, but the warrior mumbled behind his black litham in a tongue neither traveller could understand.

Tony laughed. "Depend upon it, Henri, that's your goumier who visited us last night."

"He is no meharist of France, he wears not her uniform," retorted Henri. "He is a solitary meharist, a Tuareg out of the Hoggar, looking for baksheesh."

When the French youth, however, offered their helper a silver coin, the Tuareg spurned it, lifted his shield in salutation, and rode off into the silent spaces of the desert. The representatives of the House Jambonne did not seek payment.

The Crimson Caterpillar having been given a drink of water as well as her drivers, the Wadi Meya was reluctantly left, and she faced the desert which had swallowed up their helper at the well.

"Maybe he is in ambush, Henri, waiting to entrap us amongst yonder piles of stone," Tony said an hour later.

But Henri explained that even the swiftest mehari could not have kept pace with the gallant Crimson Caterpillar, and could not possibly be ahead of them now. "As for those stones I don't understand them."

"A Stonehenge in the desert!" explained Tony, as the car drew up alongside a great circle of stones piled at regular intervals.

"No, Tony," contradicted Henri consulting a handbook, "it is historic, not prehistoric. Here the retreat of a Tuareg army, ladened with loot, was cut off by loyal Chaambas. Each brave warrior supplied himself with a small heap of stones, so that when javelins and arrows were exhausted he could still fight on with stones. And to commemorate the great victory achieved that day when the evil marauders were slain to a man, the Camel Guards, when they pass this way, always add further stones to the original tiny heaps of the warriors."

Towards evening the ground caused the Crimson Caterpillar some considerable difficulty. The caterpillars sank deep in the fine marl, and the wheels sent whirling skywards clouds of white dust that must have given notice of their arrival to watchers in Fort Inifel.

But there was no detachment of the Foreign Legion or the Camel Guards occupying the Fort when, at dusk, the cousins came to Inifel. The only occupants of the Fort were two wireless operators.

"There is a mad message awaiting you of the car," announced one of the men.

It was in cipher, and Henri decoded it with little difficulty. It was similar in purport to the message received at Touggourt. "Avoid all white men, and proceed at topmost speed to deliver the salt."

Said Tony lightly: "One would think the delivery of a few bars of salt a matter of life or death."

"It often is—to desert folk," said Henri gravely.

By the light of wicks floating in oil Henri set down the coded message for the wireless operators of the Foreign Legion to transmit to the factor in Algiers.

"The Customs troubled us at Ouargla, but all well and we go on quickly to our goal," was Henri's information which set the half-caste in Algiers stumping up and down his secret room, with the giant Kabyle sitting outside trembling.

Soon the Kabyle was summoned to accompany his master to the wireless depot, and a message was sent to an Arab agent of the House Jambonne in Taman Rasset.

Henri Leprince had been instructed to avoid this place, but must needs pass within some twenty miles. Panicky instructions were sent to the Taman Rasset agent to intercept the Crimson Caterpillar and deliver the following message: "The best bar must be delivered intact to our customer in Tim or fees will not be paid."

Jambonne's agent instructed an Arab, who had never sighted a motor car or seen an illustration of one, to take a written message to the above purport.

The ignorant Arab expected some sort of quadruped that rolled across the desert, an animal which had no legs, and snorted as it emitted its breath from its tail. Whether the Arab actually sighted the Crimson Caterpillar, or whether the man failed to intercept the car, I cannot say, but Henri never received the frantic message.

Certainly Tony, when passing through the district adjoining Taman Rasset, saw a motionless Arab meharist suddenly spring into life to flee incontinently from the shadow car gliding ghostily over the moonlit desert sand.

But this is anticipating the Crimson Caterpillar's progress. We left her at the deserted fort of Inifel, where the two French wireless operators found accommodation for both car and cousins.

It was the soundest sleep that the two travellers had enjoyed since leaving Touggourt, and they slept till the sun was high in the sky.

For the next few days, indeed, the Crimson Caterpillar went onward till late at night, the travellers having learnt that it was best to rest for a long period during the sweltering hours when the sun held sway. Under the light of moon or stars, with their headlights gleaming like silver on the sand, the car could make cautious progress without the engine getting overheated, as it invariably did in the torrid atmosphere of the Saharan noon.

So, by stony plateau, through gorges and defiles, by deserted bordj, through a land of thirst where camel and rider had met death in the past, over a yellow-red plain where the wheels of the car would have sunk hopelessly but for her caterpillars, by Saharan village whose kaid came forth at dawn to wish them Sabbagh el Kheir ("the top of the morning")—on, on to where the land grew greener and irrigation canals proved the presence of man, the travellers came to Insalah, the great oasis of the desert, with its palm groves and crenellated white walls.

There, however, their stay was only long enough to allow a skilled mechanic to overhaul the car and adjust the self-starter, whilst Henri and Tony attended to the purchase of provisions for the onward journey.

The Crimson Caterpillar, reconditioned, with full stocks of water and petrol, gaily swept onward from Insalah across the immense plain ahead, where the pale ochre of the desert imperceptibly intermingled with the bronze blue of the firmament. Twenty miles an hour was the Crimson Caterpillar's average that day and night.

Soon mountains crept up the skyline to the left. On inquiry Tony was told: "They are the mountain ranges of a land bigger than your Wales, mountains that are ten thousand feet in height. A whole country which was put down on the map as an 'oasis'!"

"An oasis as big as England!"

"Undoubtedly," declared Henri. "Your British traveller Buchanan climbed to six thousand feet in these mountains, and has written records of this little known land. Away in its inaccessible interior dwell the Tuareg raiders, who still pay loose allegiance to La Belle France."

"It's a jolly good thing we haven't to cross that country," Tony remarked as the mountains loomed higher and higher to their left.

"We may have to skirt some foothills of the Hoggar and negotiate some gullies before we once more reach the desert proper, my Tony," Henri explained.

Soon the Crimson Caterpillar was cruising quite close to high cliffs, and then she suddenly went gliding down through a narrow defile where the temperature equalled that of an oven.

It was not the sort of place to break down in the heat of the day, but some malign influence seemed to pursue the Crimson Caterpillar at this stage of her journey. First she got jammed at a narrow turn in the precipitous pass, and it took half an hour to get her free without damage to her chassis. Then, with the fearful heat of the inferno between the cliffs, the radiator boiled till it was useless pouring in more water.

"We must stop and cool," declared Henri, sweat pouring in a cascade from his face.

"Can one cool inside a furnace?" queried Tony, mopping his brow with a blanket.

An appreciable lowering of temperature in the radiator presently allowed the Crimson Caterpillar to proceed over the boulders and rocks of the narrow pass.

And then a perished tube caused one of the tyres to go flat.

It was another hour and a half before the cousins had changed tubes.

"This is our worst day yet," said an exhausted Henri as the sun went down and found the Crimson Caterpillar still floundering through the rocky defiles over the boulder-strewn way.

Tony was driving, in order to give Henri a rest, and he tried to force some pace out of the sorely tried car, but midnight found the travellers still struggling with the difficulties of the defiles.

"We must give up the contest for the present, Tony," said Henri as he held his eyelids open to prevent himself falling to sleep.

Tony drew up in the shadow of a rock that was shaped like a negro's head. It was known to the marauding Tuaregs as the Black Goblin Eyrie.

Tony tumbled from his seat, so stiff that he actually rolled to the sand.

"And this, Henri, would you believe me? is Christmas Eve," cried Tony. "Personally I am not going to hang up my stocking or wait to spy on Father Christmas."

"It is certain that we ought to watch in turn, for the Tuaregs descend from the mountains to raid passing caravans at this spot. I did not point out certain gruesome relics we passed an hour ago, mon brave," said Henri, yawning with his head lolling helplessly on his slumped shoulders.

"I would rather be murdered than go without sleep," growled Tony, settling down in the sand.

"Pray the Good Lord that no evil visitor come here this night, Tony," breathed Henri reverently. "It is certain that neither of us can keep an eye open another minute."

And so it was that when, in the grey of Christmas dawn, the Veiled Ones came to the Black Goblin Eyrie, they found two youths deep in dreamless slumber.


CHAPTER VII
THE VISIT OF THE VEILED ONES

DOG-TIRED, Tony and Henri had not pitched tent, but flung themselves down in the sand, where the moon flung the shadow of the Black Goblin Eyrie over them like a shroud.

The cliffs of the rugged gorge rose tier on tier to the sky. But from the Goblin Rock Eyrie to the desert wastes a dozen miles ahead the gorge ran due east.

Over the edge of that distant world of desert crept the harbingers of coming day.

It was the first flicker of dawn on Tony Mase's eyelids that made the English boy stir. He woke from a dream in which Gaston Jambonne had stood over him threatening to brain him with a bar of salt unless he showed the hiding-place of the man with the crooked nose. Even when he woke he could not disabuse himself of the idea that he was menaced—that someone was watching him.

He collected his scared thoughts, and stole a glance through half-opened lids at his cousin Henri. But his fellow-traveller lay face upward to the sky, breathing loudly, still asleep. Henri was not watching him. But someone was!

Tony turned on his side, saw the distant patch of sky far away on the verge of the desert, watched the rays of light deepen in the funnel of the ravine stretching eastward.

Suddenly the golden orb of the sun blazed up over the rim of the desert, shooting shafts of light to the very zenith of the heavens, chasing the last star from the sky.

There came a sudden stir, and Tony looked up to see the ravine palpitate with life—human life. He shook Henri's shoulder, which was silhouetted against the light.

"They've come," the English boy cried.

"Who?" queried Henri sleepily, peering blindly through half-opened lids.

"I don't know," Tony responded, and pointed to row after row of robed and veiled figures grouped before the Crimson Caterpillar.

"Pinch me, Tony, to prove I am not astride a nightmare," cried Henri. And, his cousin acting forthwith, sprang to his feet with a yell. "The Veiled Ones!"

Indeed it was a sight to make the bravest tremble. Immobile figures which had seemed part of the sand in the darkness, now flashed into life as the rays of the rising sun reached them.

"Thousands of them—the robbers of the desert," exclaimed Henri aghast. Which was an exaggeration, though an excusable one.

Certainly a hundred pair of eyes were focused on the waking youths, eyes that looked over the black litham of the Tuareg—the sinister warrior of the Sahara. The black webbing of the litham was wound round and round the lower part of the head and extended in thick folds to the chest, whilst above the brows was a turban, so that only a narrow strip of white face was visible. From shoulder to sandalled feet a robe of faded blue covered their virile forms. Each man wore suspended from his neck a black cord from which hung a cluster of small leather wallets—"amulets of Allah," as the Mussulman termed them, for the Tuaregs were Mahomedans of doubtful orthodoxy. At each warrior's side was girded his sword in a leather sheath. In one hand he bore a shield in the other a spear.

Henri recovered his presence of mind. "Sabbagh el Kheir. Allah karim," was his Arabic greeting to the assembled host.

There came a low chorus in response. It was in Tamashek, the language of the Tuaregs.

Then in unison the Tuaregs stooped to remove their sandals; it was the time of morning prayer.

"What are they going to do?" asked Tony.

"What we ought also to do," responded Henri solemnly.

The Veiled Ones, having removed their sandals, turned their bodies to face Mecca, extended arms above their head, crossed hands over the chest, repeated prayers from the Koran, then, placing hands on knees, they knelt and touched the sand with their foreheads. All of which was executed with the utmost reverence, to the accompaniment of a sort of chant.

"Perhaps it is as well that we imitate the heathen, only in our Christian way," said Henri quietly.

"Right-ho!" agreed Tony shyly.

So in that lonely desert place, morning prayers to their Maker rose from Mussulman and Christian alike.

When Tony opened his eyes again and rose to his feet, he felt that all fear had vanished, and he was ready to face whatever happenings this gathering of armed nomads might precipitate.

Prayer completed, the Tuaregs turned about and filed slowly past the Crimson Caterpillar, each warrior placing his finger tips to his brow as he passed the cousins and strode solemnly back to the bend in the defile where the Black Goblin Eyrie cast deep shadows.

"Doesn't look as if they meant to murder us, Henri," said Tony cheerfully. "They are riding off. Listen!"

There came to the cousins' ears the sound of grunts and swearing, of camels being released from the knee ropes that had tethered them.

"They are preparing to carry us off into captivity, my poor Tony," wailed the French youth. "But I'll punch your head, my boy, if you as much as flicker an eyebrow in fear."

"Where will they take us?"

"Probably to some inaccessible mountain retreat where Europeans have never penetrated, my poor cousin. Oh! Tony, why did I bring you on this journey of terror?"

But Tony had sprung to the driving wheel of the Crimson Caterpillar. "They haven't collared us yet," he cried. "Jump in, Henri." The French youth, however, was not quick enough.

Swiftly four stalwart Tuaregs came riding up on camels, filing by the car, then turning around and completely blocking the pass. From the shadows of the Black Goblin Eyrie came the roll of the tobol, or war drum.

The four riders bore the leather shield, the tapering spear, the girded sword. Henri and Tony grasped the revolvers in their pockets; they could not hope to overcome the Tuaregs, but they determined to sell their lives dearly.

The tobol rolled unceasingly.

One of the meharists, a chief to judge by his noble bearing and distinctive headgear, spoke. His fearless eyes singled out Henri.

"Hast thou anything to say to us, O Frank of the Engine?" he demanded in passably good French.

"Nothing, O valiant leader," responded Henri calmly. "Save only that I travel hence on my employer's business, and permit none to stay me."

These bold words seemed to please the Tuareg chief. "Thou art a man, though but a fledgling in years. Give us but a bar of salt, and you may continue your pilgrimage."

"Nay, chief, the salt is not mine," answered Henri. "It is the property of one Gaston Jambonne, a factor of Algiers, and we deliver the salt to his agent in Timbuctoo."

"Well spoken, O Frank of the Engine. Proceed on thy way." And the Tuaregs, at a word from their chief, filed past the Crimson Caterpillar to disappear in the shadows about the Black Goblin Eyrie.

"Now you see, my Tony, how precious a bar of salt may be, when a Tuareg army beg for a bar," said Henri, seating himself alongside his cousin.

"Tosh!" exclaimed Tony. "If they really wanted a bar of salt, they had only to take it. We couldn't have stopped them."

"There is honour even among Tuareg raiders, Tony," said Henri. "Above all when it concerns so precious a commodity as salt."

"Your explanation isn't good enough," retorted an interested English boy. "I want to see more of our friends the Tuaregs."

And before Henri could prevent him, Tony had jumped from the car to the sand—to go running to the bend in the pass where the camels had been tethered.

The band, however, were already on their way whence they had come. Such as were not mounted were summoning their steeds by name.

"Owrak!"

"Ajarnelel!"

"Tebzow!"

"Aweena!"

"Korurimi!"

And the beautiful, fleet-footed creatures, with their big, brown, liquid eyes, gave answering grunts to their masters' cries.

Releasing the knee ropes, the owner slapped his beloved steed's flank. The faithful camel knelt, and the Tuareg adjusted the slender riding saddle of his kneeling friend. No sooner perched on his saddle was the warrior than the mehari rose and, soft padding, swayed off with long strides after its companions. The riders, with words of endearment and gentle pressure of sandalled feet at the nape of the camel's neck, rose and dipped with every stride of the strange steed of the desert.

The chief was the last to ride off, following the cavalcade before him. He turned about in his saddle and waved a hand at the fascinated English boy who watched.

"All success to the great venture," he cried in French. "Au revoir!"

Henri came hurrying up to Tony. "Now you see how a Tuareg chief regards our conveyance of a cargo of salt as a great venture, my disbelieving cousin," he exclaimed triumphantly.

But Tony was gazing after that disappearing band of men mounted on camels, enthralled by the romance of it, charmed by those weird creatures of the sand wastes bearing their masters to some desert Eldorado amongst the mountains where French or English had never penetrated.

"One lesson you have learnt, my Tony," continued the insistent Frenchman—"how great a value a saltless man may place on a bar of salt."

"M'yes," was Tony's comment, but it could scarcely be termed an affirmation. "Mystery is all about us," he murmured under his breath. "Au revoir, the Tuareg said; I wonder when we shall see him again."


CHAPTER VIII
THE DESERT OF DESERTS

THEIR camp under the Black Goblin Eyrie, their strange visitors the Veiled Ones, their interview with the French-speaking Tuareg—all seemed but the fleeting vision of a night, as the two motorists in the Crimson Caterpillar came out from the gorges that debouched on the Tannesruft, the Desert of Deserts, as Henri termed it.

"Strange sort of Christmas Day," remarked Tony, as the car drew up at a small well under some scarecrow palm trees beside a ruined fort.

"But yes, my Tony," agreed Henri. "And look! we are not without visitors to our Christmas dinner." He pointed to three camels munching the scant herbage under the palms.

"But they won't join us in turkey and pudding," laughed Tony.

"Their owners might," Henri retorted, and indicated three black youths who came running from out the ruined stone building.

Bounding over the intervening ground as if it were rubber, the three young men, in grey-blue robes girt up about their thighs, with nothing on their heads except a woolly mop of crisp curls, stood at attention by the Crimson Caterpillar.

"Who are you?" Henri asked.

"We are of the House Jambonne," responded the three simultaneously in tolerable French.

"Your names?" demanded Henri, descending to the ground.

"I am Abdul to mend the Crimson Caterpillar," said the first.

"I am Baruch to cook your Christmas dinner," said the second.

"I am Constantine to guide you across the Tannesruft," said the third.

And then in triple chorus. "We are brothers, and of the House Jambonne, messieurs."

Tony grinned as he stepped down from the driving wheel. "I believe you," he laughed. "And unless you speak in alphabetical order, I shan't know one of you from the other."

The three black fellows grinned an identical smile, revealing similar sets of teeth, and the same number of wrinkles at the corner of their laughing eyes—Henri averred. It seemed as if they understood Tony's pleasantry about speaking in alphabetical order.

"I," said Abdul, "have been trained in a garage in Algiers in the service of Monsieur Jambonne."

"I," said Baruch, "have cooked under the eye of the giant Kabyle of Monsieur Jambonne."

"I," said Constantine, "have brought my brothers hither, as my master Monsieur Jambonne desired."

"It's evidently all planned by that master mind in Algiers," exclaimed Henri in admiration. "What care does the great Gaston take even in so small a matter as the transportation of a cargo of salt!"

"Can't see how it pays him—though it must!" a practical Englishman commented.

Both cousins, however, were content to follow the grinning Baruch to the tumbledown barracks ahead without further questions, leaving the car in Abdul's care.

Some degree of coolness was found within the stone walls half buried in sand. It was almost dark within, but Constantine contrived to adjust a looking glass in the entry in such a way as to reflect the sun's rays on the one long stone table with its bare stone benches.

"Flood lighting of the banqueting hall!" exclaimed Tony, laughing as he collapsed on the bench and surveyed the table.

It certainly was an unexpected sight—that banquet in the wilderness, the strangest Christmas dinner that two Europeans ever had sat down to eat, Henri declared.

There were dried dates in plenty, but they were built in the form of a mosque with minarets all red. The date mosque was flanked by two syphons of lemonade. ("There was a third but it went pouff! with overheat," Baruch explained.) A dish of almonds and raisins was supported on either side by a tin of compressed beef, each tin with its tin-opener. At one end of the table rose a pyramid of oranges, the summit fruit stabbed with toy flags, the Tricolour of France, the Union Jack of Britain. At the other end of the table was a loaf of bread and a small hatchet. Whilst in the centre was a space outlined with dainty Moorish coffee cups. And over all there was a pervading aroma of roasted coffee bean.

"A master of organisation," cooed Henri, sniffing the redolent air. "A very Napoleon of commerce."

The French youth referred to the factor in Algiers; and, looking round on the good cheer, even Tony refrained from criticising Gaston Jambonne.

Baruch had left Constantine to do the honours as host, and that grinning black boy showed the travellers to an ante-chamber where was a bowl of water in which to wash.

Henri was in an ecstasy as he plunged his dry, sand-seamed hands into the lukewarm, turbid fluid; it was a luxury that only the desert traveller can appreciate to the full. "You deserve the Cross of the Legion of Honour, Abdul, Baruch, Constantine—whichever of you it is."

"Good old A.B.C.!" agreed Tony as he swilled his face.

After that Constantine insisted on performing the age-old ceremony of washing the visitors' feet. The same bowl and water had to do duty, for water is too precious a commodity in the desert to fling away without using to the utmost. Towels were not necessary; the drying Saharan atmosphere did all that a towel could do.

Out in the torrid sunshine Abdul was examining the Crimson Caterpillar with an expert's eye.

In the grilling heat of the cookhouse Baruch was completing the Christmas feast.

Constantine raised the white men's cleansed feet to rest on the stone bench alongside the banquet.

"We recline at meat, as did the Romans," quoth Henri loftily.

"The dinner is served," shouted Baruch from the cookhouse, and almost pranced into the room bearing a steaming Christmas pudding on a big tin plate.

Now a steaming hot pudding in the midst of the Sahara's torrid sands is all the nicer for cooling. So the travellers partook of the other courses before tackling the Christmas pudding.

The bully beef was duly coaxed out of its tin, the loaf of bread was duly divided with the hatchet (the hatchet was not an inappropriate utensil to deal with a loaf that had been "new" in Algiers), and the syphons gave up their contents less wastefully than their explosive colleagues had done.

The Christmas pudding was "just the right temperature," as Tony remarked, when its turn came. And when the pudding had been followed by hot coffee with condensed milk, Henri and Tony were perspiring so freely that they doffed as much clothing as was decent and presently fell into a delightful doze.

When they awoke, Henri informed the gratified A.B.C. that never had been, never was, never would be such a Christmas dinner in the annals of Saharan travel, adding that Monsieur Jambonne was indeed a master of organisation in arranging such a feast at such an outlandish spot.

Not till sundown was Abdul satisfied with the running of the Crimson Caterpillar; and Henri would not hurry him.

"It's three hundred miles before we can count on meeting another human being," said the French youth, "for even the raider won't penetrate the Tannesruft, seeing that in that dead world of sand and solitude there is nothing to raid—no caravan, no hut, no water, no fuel, no human, no nothing."

"Then why on earth do we travel so desolate a way, Henri?"

"Because only by so doing can we hope to reach Timbuctoo in twenty days, my Tony."

So under a sky that might have been purple velvet spangled with sapphires, the Crimson Caterpillar set out on a journey which few men had been known to traverse in the whole history of the Sahara.

On the top of the consignment of salt in the rumble sat Constantine, who had been ordered, he said, to be their guide across the Desert of Deserts. Six months before he had mapped out the way, though so strenuous had been his task that his companions and both their camels had died before he himself had staggered on bleeding feet into Teen Zouaten, the oasis on the further side of the Tannesruft.

"Strange that Jambonne should arrange for your salt journey before ever he had met you," remarked Tony.

To which Henri, in his crushing manner, replied: "It is thus, my ignorant cousin, that the Napoleons of commerce achieve their biggest coups."

Tony didn't argue, he merely remarked "Rot!" to his boots.

Constantine, scanning the stars, gave Henri the general directions that the Crimson Caterpillar must take. The added weight of a full-grown, hefty youth like Constantine caused the Crimson Caterpillar to sink ominously in the soft sand.

Heaped by the wind into turrets, the sand stood three and four feet high with depressions between that were difficult to negotiate, whilst about the track—if such it could be called—rose dunes of sand hundreds of feet in height.

The headlights of the Crimson Caterpillar helped Henri to negotiate most of the ups and downs, but an hour after midnight the car stuck hopelessly in a bog of sand that Tony declared was a pit of soft cement in which the Crimson Caterpillar would abide henceforth.

It was an ominous spot whereon to get lost; a labyrinth of sandhills stretched in every direction.

Constantine and Tony descended, and dug the sand from under the wheels, while Henri sat trying to coax the Crimson Caterpillar to shift.

Sacks were spread for the caterpillars to pass over, whilst white and black boy shoved at the tail-board.

At the fourth attempt the Crimson Caterpillar lurched forward and kept going. But it was a trying journey, and Tony relieved his cousin at the wheel for a couple of hours.

The tired youths welcomed the glimmering dawn with a sandy cheer, their throats were dry, their eyes red with want of sleep and strenuous staring, their limbs were stiff.

Tony staggered to the ground and rolled into the blanket that Henri flung him.

Henri followed suit with another blanket, but Constantine refused to leave the rumble. He sat and watched the dawn.

"It's all right, sirs," he said. "It's all right!"

Had the two Europeans not been so utterly worn out, however, they would have noted that the customary grin was absent from the African's face. They were too dog-tired, and not sufficiently versed in the ways of the desert, to see signs that drove the grin from the sable face.

As they slept a pink mist rose and floated in the air. It continued to rise, turning from pink to an ominous red, rising in eddies and drawing nearer.

Though the sun was higher in the heavens, the day grew darker and the sky took on the colour of raw brick, whilst the rays that pierced the growing fog gave a weird light to the landscape.

Constantine felt the first slap of sand on his face.

He could restrain himself no longer: the sleepers must be warned.

"Awake! awake, my masters," he cried, as he jumped from the rumble to the sand and ran to shake each youth in turn. "Awake! Awake!! Awake!!! The sirocco is upon us, and marks us down for death. Awake! Awake!! Awake!!! lest your blanket be your winding-sheet, and your bed be your grave. Awake! Awake!! Awake!!!"


CHAPTER IX
THE ARRIVAL OF AA

CONSTANTINE'S shrill call awoke the sleepers—that, or the sudden clamour of the sirocco whistling about the Crimson Caterpillar.

Travellers and explorers have alike painted the perils of a desert sandstorm, and voyagers on palatial steamships passing through the Suez Canal will recount the horrors of the sands that assailed them when they were—comfortably penned in their cabins!

Out in the desolate wastes of the desert, however, under an open sky, the sandstorm is a tragedy indeed. Whole caravans, numbering a hundred souls, travelling only on the edge of the Tannesruft, have been engulfed; a solitary camel-rider, on a seasoned mehari, alone surviving to tell the tragic tale. More often a sandy shroud descended on camels and humans alike, their grave only to be revealed a dozen years after, when gleaming white skeletons publish the annihilation of yet another caravan.

"Rather solid air!" remarked Tony, as he woke and wiped his mouth, blinking the sand from his eyes.

Henri and Constantine were already at work endeavouring to protect the Crimson Caterpillar from the inroads of the driving grit and sand, and Tony could see them like wraiths moving about a winged monster.

"Come and help!" screamed Henri, struggling with a tarpaulin. "The sand is invading everything."

Nostrils, mouth and eyes proved the truth of Henri's statement. Tony rushed to the rescue.

The sun, from being a great golden luminary, became an inadequate red lamp hung in the sky, gleaming fitfully through a thick curtain of driving sand. Minute by minute the storm grew in fury, spattering against the Crimson Caterpillar like shots from a machine gun. The carburetor was soon choked with dust and grit. The efforts of all three youths were necessary to make safe the precious car on which their salvation depended. They struggled manfully to cover the car and protect their provisions and water supplies from destruction.

At last all that was humanly possible had been done, and with the sandy air making breathing difficult, the two European youths took refuge in the car, whither Constantine refused to follow them.

The African lay in his blanket on the sand beneath the rumble.

Within the car the youths composed themselves to some sort of troubled slumber when there was a sandy hail from beneath.

Henri bounded from his seat. "What calamity threatens us now?" he cried in tragic tones.

"Two seni-seni come," cried Constantine.

Henri gripped his revolver, stepped cautiously from the car, followed by a sleepy Tony who, deceived by a dream, thought he was on his way to the dentist—something painful, anyway!

"See! two seni-seni, there by the axle of the car," cried Constantine, grinning, whether with horror or delight, Tony could not guess.

Henri valiantly pointed his revolver at the axle, though he could, as yet, see nothing.

And then Tony exploded with laughter, causing two little birds, which Constantine had called seni-seni, to rise and flutter above the holes they had just made in the sand.

The two Black Wheatear (for such is the English equivalent for the species the African had termed seni-seni) had flown for safety to this one oasis in a cruel world of whirling sand, and not even Tony's explosive laughter nor Henri's guffaws of surprise nor Constantine's shouts of delighted discovery could drive the little sanctuary-seekers away. The little birds alighted again and bobbed their heads up and down as if apologising for their intrusion; they fixed their heady black eyes on the humans as if to beseech them not to drive them forth to face again the fury of the sirocco.

Henri whistled in a soothing cadence, and the seni-seni, as if satisfied that the two-legged travellers were not enemies, returned to their sanctuary under the front axle of the car, cowering down in their nest, there to remain till the sandstorm passed.

The seni-seni were not the only visitors to the Crimson Caterpillar that day! Though that revelation was to come later.

About midday, which was no brighter than a moonlit midnight, Constantine managed to convey to his masters some lunch.

"Boeuf à la sable," was Henri's description of the dish. "But more welcome than caviare or turtle soup at a banquet."

It certainly was impossible to get the bully beef into one's mouth without a liberal allowance of sand. It was a meal that called for much ingenuity in dispatching. Only by leaning against the car on the lee side, could the youths manage to bolt a portion of beef without being suffocated with sand.

The visiting birds were not forgotten, and fragments of the lunch were flung alongside the seni-senis' nest. But the little birds were too busy to eat; the encroaching sand made it necessary for them to shift their nest constantly upward to prevent their tiny bodies being buried.

It was after lunch that all three youths sank into a nightmarish sort of stupor, which only turned to deep sleep when afternoon brought a cessation of the storm.

Tony was the first to wake. He stood and stretched himself outside the car.

The sun was shining through a rosy atmosphere. Tony rubbed his eyes: what was that strange mound quite close to the Crimson Caterpillar?

And then his attention was attracted elsewhere. He gasped. Was he still dreaming? He uttered a cry of surprise.

Seated on the summit of the cargo of salt, on the tarpaulin flung over it, was a little stranger. The boy was not black, his skin was a greyish-white, but his eyes were the strangest feature of the strange little face, they were opalescent like those of a cat. He wore a frown on his forehead—and little else! His age might be ten or twelve years, but his serious expression made him look much older.

"Hullo, kid!" cried Tony. "What d'you want? Where on the desert do you come from?"

The boy answered Tony's English in a language unintelligible to either Tony, Henri, or Constantine. The two latter had come running up at Tony's call.

"Let him go and talk to the seni-seni," said Tony with a laugh.

But Constantine informed Tony that the wheatears had flown.

The newcomer surveyed the three youths with perfect composure from his superior seat on the top of the loaded rumble.

Henri, failing to make himself understood in French, tried Swahili, but the boy simply frowned politely in response.

Then Constantine had a go in one—two—three—four—Saharan dialects. It was the last of these that drew a reply from the little boy, and lessened the frown on his brow.

There was some interchange of halting phrases between Constantine and the boy of the frown.

Constantine turned to Henri. "The little djinn understands a few words of the Black Tuaregs, but he speaks it very badly so that I can scarce understand."

"What's his name?" asked Tony.

Jambonne's servant put the question, and the little stranger turned to Tony to reply. "Aa," he sighed. And that was his name, as further questioning by Constantine revealed.

"Whence does the little chap come?" Henri asked.

But this time, spite of much gesticulation on Constantine's part, the questioner found himself up against a blank wall.

And then Tony recalled the sand mound that had first attracted his attention. "Perhaps that may help to explain the mysterious arrival," he said as he seized a spade.

His spade struck something soft.

Tony knelt and scrabbled with his hands in the sand.

A grizzled head with long ears appeared.

"It's a donkey—cold and dead!" cried Tony.

For the first time since he had been sighted atop the salt load, Aa moved perceptibly.

Agile, graceful, with no undue haste, Aa stepped to the sand, and fell prone on the dead donkey's neck, putting his little arms about the grizzled head.

The little fellow made no sound, but when he looked up into the three sympathising faces, two white, one black, there were tears in Aa's eyes.

"Our Cupid came here on the back of that donkey, fleeing before the sand storm, separated from his caravan to find refuge on a Crimson Caterpillar," Henri summed up. "We must return the boy to his parents."

"Perhaps he didn't come alone," said Tony. "But anyhow we can't advertise in the evening paper that we've found a child."

"I did not see him come," said Constantine fearfully. "He is not of this world. He came on the wings of the wind."

However, as everyone was hungry, the discussion was deferred, as a meal was felt to be the most pressing business.

"Perhaps now we shall be able to get a smile out of him," suggested Tony as he watched Aa solemnly consume an inordinate quantity of bully beef and biscuit, swelling visibly before his entertainers' eyes.

But not a smile crossed the solemn little face, neither then nor throughout all the amazing days that Tony spent in Aa's company. Not that the tiny chap was unhappy or ungrateful, for after literally filling himself, Aa stepped up to Tony, bowed gravely, rubbed his rotundity and kissed the English boy's hand. Evidently he regarded Tony as his saviour.

Tony patted Aa on the shoulders, but the little fellow stepped gravely backward and lightly touched himself on the chest four times.

"The Sign of the Cross!" exclaimed Henri in wonderment. "Verily he is a Christian, though I swear he is no European. He has not the white skin of a Western man, he has the ivory skin of the East. His features are—are Jewish, and his eyes are—are—"

"—like cat's eyes," put in Tony. "I bet they shine in the dark, and somehow they remind me of—of—someone I've seen recently. But—I—can't—think—who."

"Constantine, ask Aa why he made the Sign of the Cross," Henri ordered.

Constantine, however, failed to get any explanation. "It is custom," was all the African servant could tell the Europeans.

As for Aa, he curled himself into a ball, and, like a kitten after a full meal, seemed to purr himself to sleep.

Meantime Tony had been pondering the whitish complexion, those shining yellow-white eyes of the little visitor.

"I have it!" exclaimed Tony, grasping Henri's arm in his excitement. "The boy is of the same race as the cowled marabout of the Hotel Djouf at Touggourt."

But though Tony put the boy through a catechism with the help of Constantine as soon as the little fellow had slept off his surfeit, he was unable to connect up Aa with the mysterious monk visitor outside the Hotel Djouf.

Too soon the onward journey monopolised all the conscious thoughts of the cousins; whilst Tony's and Constantine's physical powers were called into action again and again as the Crimson Caterpillar ploughed too deeply in the quicksand.

Hours of monotonous travelling followed, sand—sand—sand their only scenery. For two days they saw nought but sand.

At long last a green line showed up against the evening sky, and Tony gave a great whoop of delight. And there was one line less in Aa's frown. The Wadi Zouaten was in sight.

They had pressed forward through the heat of the day, for water supplies were running low, and the food had to be allowanced. Henri had not calculated on the additional member of their Mess; Aa was a wonderful trencherman.

But Henri had reached the limit of his endurance; he fell forward across the steering wheel. "We can't go further to-night," he gasped. "And you, Tony, couldn't keep your eyes open for another turn at driving."

Tony knew this was true. "Perhaps Constantine can drive," he faltered.

But Constantine preferred camels to cars, and respectfully declined to have ought to do with machinery—that was his brother Adbul's job, he explained. Also he went on to explain that, in any case, he would not accompany the Crimson Caterpillar into Teen Zouaten.

"But why, my faithful Constantine?" queried Henri. "We owe much to your guidance across this trackless Tannesruft, and would like you to join us in the pleasures of civilisation at the French fort yonder."

But the servant of Gaston Jambonne shook his head. "I have promised my master that I will hold no conversation with white men excepting Monsieur Henri Leprince and Monsieur Antonio Mase. So I may not meet the men of the French Foreign Legion in the fort of Teen Zouaten. Also I like not the last-comer to our company. He too may be of the white cattle that my master bade me avoid."

Henri was well aware that the African had been fearful of Aa ever since his uncanny arrival, but he laughed at Constantine's fears. "Surely you are not afraid of a small child, you booby!"

"It may be that the small djinn who arrived on the wings of the wind may do me no harm, but I may not abide longer in his company," said Constantine, grinning for fear rather than for fun. "Also I will now tell you that the small djinn was rummaging amongst our stores in the rumble whilst my masters slept at the last halting place."

The cousins turned their eyes on Aa, who sat like a sphinx in his usual place atop the salt cargo, frowning and gazing dreamily at the distant oasis.

"Aa is certainly uncanny," said Henri.

"But he's a decent kid," protested Tony, who had taken a liking to the scrap of humanity so serious, so grateful. "He was hungry, perhaps, when he hunted in the rumble. Perhaps he had starved for a week before he reached us; he certainly was thin when first we sighted him."

"I watched the djinn," said Constantine, "but he took not one small bean."

"Then if the kid took nothing, why worry?" Tony asked. "All kids are inquisitive, if they have any brains. And Aa has a lot."

"I come not to Teen Zouaten, I go to Ayer," concluded Constantine. "I have business to do there for Monsieur Jambonne."

"Where is Ayer?" Tony asked.

"Ayer is a little-known district of the Sahara, a country like your mountainous Wales, Tony," Henri explained. "Few white men have penetrated to mysterious Ayer. But what about a meal, Constantine? I am dying for food and sleep."

After the meal, Constantine volunteered to take the night watch, and the two cousins were not many minutes dropping to sleep.

The journey was to have been continued in early morn, but the sun was well up in the heavens when Henri awoke.

"Constantine!" he cried.

But no grinning African came in response to the call. A serious little figure seated on the rumble pointed eastward, and then to the sand below.

Tony sprang up, his Scout instincts aroused. "Two camels have been here in the night," he cried, pointing to traces in the sand.

"And Constantine has gone to his work in Ayer without wishing us adieu," said Henri sourly. "Folks would seem to do things differently in the desert to what they do in decent society."

"Mystery still dogs our steps—or rather the ruts made by our caterpillars," laughed Tony, then more seriously, pointing to the little figure on the rumble load, "and a living bit of mystery remains with us."


CHAPTER X
THE MENACE OF THE SOUDAN

CONSOLING themselves for the loss of Constantine by making an extra good breakfast, husbanding of supplies being no longer necessary now that the oasis of Teen Zouaten was in sight, the cousins reviewed the situation as they ate.

"Though Constantine may have deserted us," Henri remarked, "doubtless another agent of Gaston Jambonne awaits us in the haven ahead."

"And we still have Aa."

"Which is a doubtful blessing I hope to shed at the fort yonder," added Henri. "Look how he mops up the commissariat department!"

"He's certainly getting fatter," said Tony, scrutinising the curves of Aa's ivory-grey figure, "but his frown remains the same as ever; he must have a lot on his mind."

After breakfast the motorists drove the Crimson Caterpillar across the intervening desert to Teen Zouaten.

A French officer with native troopers awaited them outside the fort. He seemed friendly enough, but Tony fancied their movements were closely watched, and noticed that their belongings were being thoroughly scrutinised.

Seeing the mark made at the Customs inspection at Ouargla, the officer gave grudging permission for the goods to pass. "It is possible, my friends, for dutiable articles to be introduced between one desert outpost and the next. And I may tell you that we have warnings from Algiers that—but I must not betray official secrets. One is so glad to see a fellow European that one sometimes forgets, that it is one's duty to be discreet."

"My record is a clean one, adjutant," said Henri haughtily. "And I am as true a son of France as any officer in uniform."

"Certainly, my friend, I do not doubt it," replied the French soldier, smiling blandly. "But I must say I don't admire the small servant who sits on your salt as if he wanted to hatch it."

"I'll talk to you about him later," Henri said as he shook the hand the adjutant extended. "Meantime I want to find provisions and petrol."

The two cousins set about their business, and found an Arab who was ready to assist—"of the House Jambonne."

They took their midday siesta beneath some tamarisk bushes within the walls of the desert outpost.

"The desert is getting on my nerves," remarked Tony to his cousin. "Everywhere I fancy eyes are watching me."

"They probably are!" responded Henri, puffing at a long cheroot given him by the adjutant. "It is the population, after the desolation of the desert places, that worries you. Here you have the gallant officers of France, a captain and an adjutant, and a Chaamba platoon, not to mention half a dozen strangers of half a dozen races, and each of these, in this lonely solitude on the verge of an Empire, is deeply intrigued at sight of a newcomer such as you are. All eyes study the stranger, just as your eyes, Tony, are intent on each human being that comes into your ken this morning. Wherefore you find menace where there is only kind curiosity?"

"Look at that!" And Tony pointed to an Arab in a ragged cloak, watching them with unwinking orbs.

"Only an agent of the House Jambonne," explained Henri. "I saw him exchange words with our Arab dragoman of this morning."

"Look at that!" And Tony indicated the black Soudanese sentry walking round and round the Crimson Caterpillar, his white pupils flashing out of the black face, ever in the direction of the cousins.

"France looks after our property," said Henri proudly.

"Well, what about that?" queried Tony, and he pointed surreptitiously at the battlements where the captain of the toy fortress was sitting under an awning, binoculars to his eyes, studying his two visitors.

"Hélas! my Tony, you have not yet learned the value of salt and how all eyes must needs turn to that necessity of life in desert communities," declared Henri. "Nor have you realised the spell that the desert solitude has bred in your brain. . . . Sleep well, for the agent of Monsieur Jambonne is busying himself, providing for our onward journey into the Soudan."

Under the tamarisk bushes the two cousins who had not had much sleep for some days pitched their tent and slept the Old Year out and the New Year in.

Jambonne's agent had done his work well, and the inroads made on the commissariat by Aa were more than compensated for.

As for Aa himself, the French adjutant politely refused to take charge of him.

"My dear friend," the adjutant said to Henri, "were I to accept responsibility for every little wayfarer without relatives, I should have to build an orphanage twice the size of this fort. Children are an encumbrance which the raider of the desert rejects when he carries off the able-bodied as slaves, they are superfluous to the father who cannot find food sufficient for his hungry family, they are a burden to the widow whose husband has succumbed to the perils of this forlorn land. Wherefore, my dear friend, take your baby with you, I don't even know to what race or tribe he belongs."

So it was that Aa, perched on the tarpaulin above the salt, rode over the treeless plains of the Soudan towards the fertile banks of the Niger where Timbuctoo lay.

By way of the Wadi of Zouaten, the Crimson Caterpillar passed out of Algeria into French West Africa.

"A swift meharist has tried to keep pace with us ever since we left the oasis," Tony said, pointing to a distant camel and rider on their flank.

"He wanted our protection, Tony, for in these districts the desert robbers raid and do not hesitate to plunder and kill the solitary wayfarer."

Tony felt a soft touch on his shoulder. Aa was leaning over from the rumble and trying to attract his attention. The boy pointed to a waiting camel-man ahead of them.

With the aid of his binoculars the English boy saw the meharist out of Zouaten ride up to the waiting meharist. "The shadowing goes on," he told Henri.

Had the going been good, the car would have out-distanced the camel-riders very soon, but great masses of stone encumbered the onward way for the machine, though the animal's bifurcated hoofs with their leather wrappings made good progress. Henri had to back and contour continually to avoid damage to the caterpillars.

The day was stifling hot, and Tony took turns at the driving wheel when the track was less difficult, allowing his cousin to snooze.

More than once both Henri and Tony were at a loss as to their direction, and then Aa would gently touch Tony's shoulder and point unfaltering in a certain direction, his forehead creased but a kindly glance in his eye.

Whether it was on account of following Aa's directions or because Henri did not follow them closely enough, towards night Henri had to confess himself hopelessly lost amidst perplexing sand dunes, running in every direction like the strands of a spider's web.

Henri was a little out of humour, and rejected Aa's advice, given by extended finger. "Peste! I will not wind like the spring of a clock, I will go on and over the confounded sandhills. Shall a mere Soudan subdue us when we have conquered the Desert of Deserts?"

"But in the Tannesruft there was Constantine to guide us," Tony responded. "And here—"

"—we have Aa to misguide us. Not to mention the mirage meharists you keep imagining on the skyline of our flanks, Tony. No, I won't stop though I am lost. We must get somewhere, and I hope it will be the wells of Toudaten we shall reach before morning."

It must have been an hour after midnight when Aa lightly touched the cheek by Tony's ear. That is the spot that touched gently brings back a sleeper to consciousness.

"Fireflies," murmured Tony, waking and looking to the east where Aa was pointing. "Fireflies, Henri!" he said more loudly.

Henri jumped in his seat; he had been driving in a state that was not very far different from that of a somnambulist. "Quoi!" he cried.

"Watch-fires," said Tony, correcting himself as he woke to full life.

Henri, too, awoke to his surroundings and deliberately turned the car to face the twinkling lights where he might gain information of their whereabouts. "They may be enemies," said Henri lightly, "but—" The French youth shrugged his shoulders.

As the Crimson Caterpillar drew nearer the welcome lights Tony raised a shout. It was a platoon of Senegalese under a French sergeant sleeping about their watch-fires.

A sentry answered Tony's shout, and soon the lost motorists were seated about the fire whilst a black trooper toasted mutton chops on the end of his bayonet for the benefit of the newcomers.

After the meal a peaceful period of sleep for the two cousins followed, whilst Aa could have slept if he chose.

"What about that albino imp of yours?" asked the sergeant of Henri next day. "When he should have slept, the boy has been climbing under the tarpaulin and fumbling round in your rumble."

"He is one pimple of curiosity," explained Henri. "I wish you could find him a parent."

"But of what race is he?" asked the French sergeant. "I have lived a dozen years in this and similar torture holes, but I've never seen a native to match him. Where did you get him?"

"The sirocco brought him." explained Henri. "And my cousin insists on keeping him, though the cat's eyes of him give me the creeps."

"I should tell the albino imp he mustn't crawl in amongst your goods, mon vieux," recommended the sergeant. "Threaten him with a strapping."

But, seeing there was no one competent to communicate with Aa now that Constantine was gone, the sergeant's kindly meant advice could not be utilised.

The afternoon was spent in changing the rollers of the Crimson Caterpillar with the aid of the Senegalese troopers, and in the evening the travellers went on, with Aa atop the tarpaulin as usual.

The French sergeant gave minute directions regarding the onward way, and Henri sang gaily as he set the Crimson Caterpillar's nose towards the Soudan and the Bend of the Niger.

Henri's song, however, was soon dried up by the torrid heat and the flying sand that an eddying wind flung in the motorists' faces.

Twilight brought some relief from the fierce onslaughts of sun and wind, but both Henri and Tony were terribly fagged.

"See! a menagerie awaits us," Tony cried, as against the starshine queer shapes stood up across their path.

"If animals, my Tony, then of the prehistoric age," Henri explained, looking more closely at the huge rocks of fantastic contour standing up out of desert sand at all sorts of angles.

"Hereabouts one might imagine that Noah disbanded the inmates of his Ark," laughed the English boy, but it was forced gaiety.

Both cousins were too tired to go further, and decided to camp in that spot for the night, as the encircling rocks would form protection should the wind rise again.

There was no fuel for the cooking of a meal, indeed the two gallant lads were too weary to cook one. So their New Year's supper consisted of bully beef, dates and biscuits washed down with lukewarm water.

Aa ate less heartily than usual, and Tony caught him looking repeatedly towards the east in a preoccupied manner; his eyes could see more in the dark than could those of the Europeans.

"I'll keep watch," said Tony, who had done considerably less driving than usual through the intricate country they had been negotiating.

Henri was far too tired to dissent.

Setting his back against a great rock shaped like a lion couchant, the English boy peered out over the desert through an irregular avenue in the surrounding rocks. Henri slept within the car, and for once Aa deserted his eyrie on the rumble and came to seat himself beside Tony.

It was weird in the extreme, with all those uncouth black rocks mistily grouped about them, and no moon visible to lighten the darkness, and presently Tony began to believe that the rocks were coming to life to dance in a midnight orgy like the Whimble Stone was said to dance in that Mendip valley where he had been born.

One black shape, like a camel, certainly grew bigger, seemed to smell its way towards them. And he could detect something like a rider on the spectral camel's back. But was it a spectre? For another loomed up behind it. And yet another behind the second—coming nearer. And a fourth! And a fifth!

With a start that stirred Aa beside him, Tony realised that it was no dream. He might have slept, but he was awake—awake, with his heart beating fast.

A hand was placed in his—that of Aa, as if to reassure him.

A minute later he would have shouted to rouse Henri: there could be no doubt, the meharists and their riders were alive.

But a second little hand was gently placed before his mouth. Aa was very vigilant.

A sibilant call was sent forth from Aa's lips—a fivefold call in a strange tongue.

The five camel-riders came to life amongst the rocks, picked their way daintily till they drew up in a line before Aa.

Tony could see the meharists more clearly now, and what he saw made him shudder. They were clad in Tuareg dress, swathed in robes from head to heel, black litham about their faces, leaving only a narrow slit about the eyes visible. But the Veiled Ones had grey-white flesh like Aa, the same yellow, opalescent eyes!

"Who are they?" Tony asked in his excitement, forgetting that Aa could not understand.

One thing was certain, the newcomers and Aa were able to communicate freely by the spoken word.

They were quite different from any other Tuaregs Tony had seen. He would have awakened his cousin, who was sleeping like a dormouse in winter, but Aa restrained him. Strange the commanding gestures of the small person before whom the visitors bowed!

All the time they sat there, the Veiled Ones interrogated Aa—though interrogating is, perhaps, scarcely the word to apply to the deferential way in which they addressed the naked scrap of humanity.

As each meharist addressed Aa, he salaamed before speaking, raising finger tips to brow; then, as he concluded, the speaker would make the Sign of the Cross on his chest.

It was this reassuring Sign, and the fact that the midnight visitors, apparently, bore no weapons, that enabled Tony to retain his composure. Though he kept a hand on the butt of the revolver hidden in his coat pocket.

An unexpected sight in that wild desert—unarmed men! At least, no single spear, shield or sword was visible amongst those five meharists sitting motionless before Aa.

Aa made a final speech, closuring with the Sign of the Cross.

There was a fivefold gesture of similar nature in farewell.

Out of the darkness and the strange shapes the visitors had come; into the shadows and the weird stones the Veiled Ones faded away.

Aa curled into a ball and was soon asleep, whilst Tony lay awake and wondered till he too slumbered, his peace disturbed by phantom shapes that came and went in the misty land where dreams are born.

When Henri, who had slept without waking till sunrise, was told of the strange visitors during the night, he shrugged his shoulders sceptically. "With these uncouth rocks about one, in the grim night of the menacing Soudan, I wonder at nothing you may have imagined, Tony. It is quite certain, however, that no Tuareg would ride unarmed in the desert. You have been the victim of moonshine, my brave one."

"I wasn't dreaming, Henri," protested the English boy, wishing there was some way of inducing Aa to understand and corroborate. "After all, it is only a repetition of what happened in the desolate defiles beyond Insallah. Though those fellows there were armed, whilst these—"

"—hid their arms under their robes," chaffed Henri. "It may be that all the Tuaregs are merely agents of the House Jambonne."

"Or else," said Tony, tuning in to his cousin's mood, "Aa is a mascot shielding us from all misfortune."

But at that Henri grew suddenly serious. "Not a mascot," he said, "but a corpse-light luring us on to death." And he glowered at the whitish-grey complexion and the opalescent eyes of Aa who had returned to his perch above the salt.


CHAPTER XI
WITHIN EIGHTEEN DAYS

FOLLOWING the night when the five mysterious Tuaregs were seen by Tony, the Crimson Caterpillar was driven by Henri at her topmost speed across the sombre Soudan towards the wells at Tabancourt. Henri would do his utmost to reach Timbuctoo within the eighteen days specified, for the time was running short.

Indeed it seemed as if others were anxious about the car's progress, for before ever Tabancourt was in sight, from the direction of that oasis two Tuareg camel-riders bore down on the motorists, waving rifles and pointing backward on the track they had come.

Henri would have drawn up, but the meharists showed unmistakable signs of disapproval at his slowing down, and waved the car vehemently forward.

So Henri drove on at top gear, and the two Tuareg riders were left behind, specks in the desert, still waving the car onward.

"Evidently there is great need for salt in Timbuctoo," Henri said, but with less conviction than usual.

"Salt or something else," retorted Tony.

And for the first time the French youth did not argue the point with his English cousin.

As the vegetation about the wells of Tabancourt gave some life to the landscape, a second couple of excited Tuaregs rode down on the Crimson Caterpillar.

Again the riders would not parley, but waved the motorists onward.

When Tabancourt was neared, a French sergeant with a camel troop of black fellows rode out to meet the desert motorists, giving them no very friendly reception.

Henri was eager to hasten on, but needed further supplies of petrol, provisions and that scarce desert necessity—water. Besides, they needed sleep before the final stage of the journey.

The sergeant, having ousted a reluctant Aa from the tarpaulin, and having noted that the rumble bore nothing but salt and a few remaining bully beef tins, changed his behaviour towards the travellers.

"The desert makes us very suspicious, mon ami," he explained to Henri. "Also it is unnerving to see a mechanical caterpillar crawling over the sand. Yet, seeing you are bona-fide traders, we will do what we can to supply your needs. Petrol, however, is something which we have not got."

"But I'm down to my last pint, and I was told by my employer I should find some here," exclaimed Henri, aghast at the possibility of failing on the very threshold of accomplishment.

The sergeant shrugged his shoulders. "Come and eat. Afterwards we will think of petrol."

Henri garaged the Crimson Caterpillar in a sort of shed under the walls of the fort, two black troopers remaining to guard the car—two black troopers, and Aa.

Aa had returned to his tarpaulin top and refused to budge.

So Tony saw the small boy supplied with food and drink, and then followed his cousin and the sergeant, who was glad to entertain them in exchange for news of the great world out of which he had stepped five years before.

Henri tried to persuade the sergeant to accept the gift of—Aa.

"But no, sir, I care not for the look of your van boy," responded the sergeant. "His eyes make me think he hides claws."

"We must find a home for him in Timbuctoo," Tony declared. "But I shall miss the interesting little imp."

"He is such a charming conversationalist," remarked Henri in tones sarcastic. He did not like Aa, and would have liked him still less had he known what the mystery boy was doing at that very moment.

The meal with the sergeant ended, Henri insisted on setting out to the feeding of the Crimson Caterpillar. "I must have petrol," he said.

The sergeant said there was not the slightest prospect of supplies, "but you might see Solomon."

The cousins were guided to the emporium of Solomon in the native quarter.

Solomon was a coal-black gentleman who claimed to be a Jew, and spoke French and Arabic.

"You have a wonderful store, Monsieur Solomon," said Henri, as he stepped down into a basement full of odds and ends—from a vacuum flask to a bearded goat. "You have some petrol?"

"Not a single drop, Monsieur Henri Leprince," was the surprising answer, seeing that the visitor's name had not been mentioned.

"You know me?"

"I am of the House Jambonne," was the reply. "And the petrol that I had is now in the belly of the Crimson Caterpillar."

"Our Napoleonic patron does not fail us," Henri triumphantly declaimed. "Now, my Tony, we may return to the sergeant's hospitality and sleep well."

Their slumber, freed from anxieties, was a prolonged one, and when they woke, they were fit and eager to be gone.

The cousins found Aa curled up on the top of the salt in the rumble, fast asleep.

"Never seen the kid looking so cheerful," remarked Tony, looking on the little face whose frown was less marked than usual.

"He's sleeping off his meal, the young glutton," was Henri's comment. "There's not a crumb left of what you gave him, and I reckon it was sufficient for two grown men."

But Henri was unjust when he accused Aa of gluttony. A cup of water and a couple of dates was all that Aa had eaten; and two grown men, the black troopers, had consumed the rest of the meal, their connivance in certain plans of the small boy bought by this bribe and the commanding glance of those uncanny eyes of his.

Tony roused Aa lest the shaking of the rumble precipitate the sleeping cupid to earth as the Crimson Caterpillar, duly supplied with petrol as Solomon had said, set off amidst the huzzas of the black troopers and the eloquent gestures of the French sergeant.

After four hours of good going the Crimson Caterpillar was given a rest on a grassy plain, where her drivers could feast their eyes on the wonders of the bush. Wondrous indeed! after the desolation of the desert.

There were gazelle and other small deer to be discerned in the distance, and as the cousins sat quietly taking refreshment, a white oryx, chased by a lynx, burst through the undergrowth almost within revolver shot.

A griffon vulture swooped down as if he would pick Aa from his perch.

Tony promptly fired his revolver at the loathsome bird, and it flew off, croaking discordantly.

"Shouldn't like Aa to be brought up in a vulture's nest," Tony said with a laugh.

"Personally," responded Henri, "I don't care how the kid goes—as long as he does go. I never did like mysteries on two legs."

"You are prejudiced against Aa, Henri, but I can't help feeling that Aa is bound up with our fortunes, and that we may be glad of his help before we get back to Algiers."

"His help!" retorted Henri. "What help can a grey kid with cat's eyes, of no known nation, who can't twig a word you say and can't speak a word that's understandable, and who has the appetite of an ostrich—what help, I ask you, can such an incubus be?"

"I can't explain," said Tony stubbornly, "but I don't relish turning Aa adrift without a single friend."

At which remark Henri bridled somewhat but replied nothing, and a few minutes later set the Crimson Caterpillar careering forward over the fertile plain.

At night they came to the fort of Bourem.

"The Niger!" cried Henri, drawing up and pointing to a silvery expanse lit by moonlight, sparkling and dancing on the face of the water. "I breathe it. It animates me. The goal is in sight. We have accomplished an epic journey, my cousin. In two days we shall deliver the salt in Timbuctoo, into the hands of Sidi ben Baar."

"Unless the Crimson Caterpillar breaks down," interpolated the English youth, who was inversely gloomy as his French cousin effervesced. "And unless Soudanese robbers raid us between Bourem and Timbuctoo; and unless Sidi ben Baar is dead; and unless—"

"By the Tower Eiffel! you English misérable, how dare you prophesy disaster when ma chère Caterpillar is just palpitating to carry us on.... Yet, let us feast our eyes, my unpoetical one, on that historic highway which the Arabs call El Bahr, the sea!"

The cousins stepped from the car, and, standing in the shadow of the mud walls of the little fort, looked out over the track leading onward by the Bend of the Niger to the city of Timbuctoo.

Aa stood at Tony's elbow. He was frowning more intently than ever, and the eyes of him shone with metallic lustre. He tapped Tony's knee, gabbled something in his strange tongue, and gazed earnestly into the English face which he had learned to trust.

Tony stared in surprise and consternation. "Hark! Henri, Aa mentioned the name of Sidi ben Baar." He turned to the little fellow at his elbow: "Do you know Sidi ben Baar?" he exclaimed.

"Sidi ben Baar! Sidi ben Baar!!" repeated Aa. And he deliberately spat in the sand, his eyes gleaming with something like hate. Then, pointing in the direction of Timbuctoo, he shook his head vigorously.

"Aa, at any rate, doesn't want us to reach Timbuctoo," Tony declared as he watched the mysterious mite, turning about as if to run back the way the car had come, and grabbing hold of Tony's hand as if to drag the English boy with him.

"Sidi ben Baar is no favourite of Aa's, it would seem," said Henri. "I wish the boy could communicate his thoughts to us. I am beginning to think with you, Tony, that there is more in our journey than mere salt. There's black magic somewhere, and I believe it is concealed in that grey atom at your elbow."

Tony turned to the frowning, tugging kiddy. "I bet there's no wickedness in you, Aa, is there, laddie?"

The answer wasn't exactly reassuring. Aa almost snarled "Sidi ben Baar!" and again spat in the sand with the utmost signs of dislike.

"We'll deliver that salt—and Aa as well—in Timbuctoo," said Henri gazing with something like fear at the little fellow frowning so frightfully.

It had been planned by the cousins that they would have an hour's sleep at Bourem, and then drive on through the night as long as one or the other could keep awake to drive. Henri was to sleep for the first hour, whilst Tony watched; then Tony was to have his turn of sleep.

Everything went according to plan in those two hours. All the time, however, Aa slept not one wink; he sat on the tarpaulin above the salt and stared ceaselessly towards the city where the cousins would fain be.

And then came the first hint of disaster to all their well-laid plans—a wind had risen whilst they slept, and the eddying sand must have worked into the bearings of the Crimson Caterpillar. But whatever the reason, the car, when Henri would have started her, refused to budge.

Although there came to their rescue a black man—"of the House Jambonne"—from out the darkness, this time the Algerian factor's agent was rather worse than useless; for when Henri would have been busy at lubrication of the car, the black would keep jogging his elbow, urging him to go on by waving arms wildly in the direction of Timbuctoo.

"It's all right, my black semaphore," protested Henri with heat, "you just leave me alone or I won't promise not to hit below the place where you would wear your belt—if you had one."

It was Aa who finally rescued Henri from the attentions of the black man. He circled about the newcomer in the darkness with a pointed stick, jabbing it at the interfering agent of Jambonne until the persecuted black grew wild with rage and made rushes at his tormentor. But the black man might have grasped a rainbow sooner than get a grip on the elusive little grey atom.

The tormenting of the "House Jambonne" went on through the night together with the lubricating of the Crimson Caterpillar. Henri worked like one possessed, refusing to allow Tony to touch the car. The French youth, usually so buoyant, was suddenly stricken with a sudden fear that the Crimson Caterpillar would never enter Timbuctoo.

But long before dawn Henri had the satisfaction of getting the car going, at a better speed than she had shown since setting out from Touggourt.

"The Crimson Caterpillar must reach Timbuctoo this coming night," Henri declared between clenched teeth, "or we fail to fulfil our contract."

The cousins drove on through that day without a halt, taking turns at the wheel and at sleep. Yet whenever the Europeans looked up at that tiny grey figure on the tarpaulin, they saw him with eyes intently fixed on the track ahead as if he were momentarily expecting something—or someone! Thrice, at different times when passing a distant clump of vegetation, he was heard to give a fivefold whistle, low and shrill.

It was dusk when the walls of Timbuctoo were sighted.

Yet before the gates of the city were reached, there came a posse of horsemen galloping madly down on the car, discharging rifles in air and brandishing long Tuareg spears.


Illustration

They were all veiled, and the leader's piercing black eyes glued themselves on Henri, who did not halt.

"Here you must wait, Capitaine Leprince," the newcomer cried in tolerable French.

"For whom?" shouted Henri, not slackening the speed of the Crimson Caterpillar.

"For Sidi ben Baar, who will come to you here," the Tuareg screamed above the purr of the engines.

"I was told to deliver the salt in Timbuctoo," shouted Henri, "to Sidi ben Baar himself, and no other."

A dozen rifles were pointed at the Crimson Caterpillar.

Had he himself been threatened Henri would have probably gone gallantly forward, but he could not contemplate the catastrophe of a shot in the vitals of the Crimson Caterpillar.

Henri drew up the car with a jerk.

Tony glowered at the Tuareg pointing a rifle at his head; it was maddening to be held up on the very threshold of success.

Aa, crouching low on the tarpaulin, sent a shrill, fivefold whistle echoing over the desert sand.


CHAPTER XII
SIDI BEN BAAR ARRIVES

HENRI glared haughtily at the Tuareg riders who dared to stay the onward dash of the Crimson Caterpillar.

"How soon does the Sidi ben Baar honour us with his presence?" he asked. "Why may I not meet him in the public square of Timbuctoo—the Place Joffre?"

"That can never be," said the Tuareg leader. "Yet have patience, Capitaine Leprince, even now the Sidi is on his way. Look yonder to the city itself and you will see him being borne hither."

Henri and Tony used their binoculars forthwith and were able to see a procession of horsemen surrounding a palanquin issuing from the castellated grey brick gate of Timbuctoo, with a distant background of quaint mosques and stumpy, crenellated minarets showing above the city walls.

"It looks like a town of old Egypt," remarked Henri. "I hope we rest within the walls to-night. All seems to be shaping well, though I don't much relish this secret meeting with the Sidi outside the walls, as if we were engaged in something not quite straight."

"There was mystery when we started on this journey," declared Tony, "and I guess there will be mystery right up to the finish." But little did Tony imagine where their adventures would finish!

Henri was all excitement and elation as the gilded palanquin drew near. "Behold the Sidi ben Baar arrives, my Tony, and we will deliver to him the salt bars that ma chère Caterpillar has borne from Touggourt to Timbuctoo within the eighteen days specified. We have earned the second hundred English pounds sterling promised us by Monsieur Gaston Jambonne. Our mission is accomplished, mon brave."

But Tony was watching the approach of the gilded palanquin with as much apprehension as Aa; on Aa's face was a look which was difficult to diagnose, a look in which triumph and hate and fear mingled.

Swiftly the stalwart black bearers bore Sidi ben Baar to the spot lit by the headlights of the Crimson Caterpillar.

The Veiled Tuaregs on their spirited Arab steeds still menaced car and drivers.

The black bearers set the gilded palanquin alongside the most modem invention in cars; it was a strange contrast!

A turbaned head appeared from out the silk hangings, fierce eyes in a bearded face glowered upon the cousins.

"You come from Gaston Jambonne, roumis?" was the harsh query in Arabic.

"We come from the Algerian merchant, Monsieur Gaston Jambonne," responded Henri proudly. "Are you the Sidi ben Baar?"

"I am that prophet," came the haughty response. "Are you the Frenchman, Leprince?"

"I am Monsieur Henri Leprince, servant of France," responded the French youth, and he was no less haughty than the Arab. "And I come to deliver to you the salt at Monsieur Jambonne's desire."

"Have you the best bar—the best bar?"—this in Arabic, and then in French the autocrat in the palanquin repeated: "Have you the best bar?"

"It is safely stored at the base of the pile in the rumble," replied Henri. "I will hand it over to you now, only asking that you will sign the note that it has been delivered," and Henri produced a small note-book.

The fierce Arab in the palanquin barked an order, and the Tuareg horsemen sprang from their steeds as one man.

Sidi ben Baar, helped by obsequious servants, stepped from his primitive carriage and signed to the Tuaregs to unload the salt from the rumble.

Aa clung to his perch to the last moment, but was forced to come down by the dragging of the tarpaulin from the top of the goods in the rumble.

The Sidi's keen eyes were glued on the salt bars as they were lifted to the ground, one by one, to be borne to the Arab's feet.

"Sidi ben Baar looks for the crescent that Gaston Jambonne scratched on the best bar," said Henri in an aside to his cousin.

"And see how the old tyrant makes them turn over the bars to see if the sign is on the under side," added Tony, watching closely.

A torch was held aloft by one of the Sidi's men; the sub-tropical evening was hastening the desert into darkness.

When there were only two bars of salt left in the rumble Tony caught sight of the crescent symbol that Gaston Jambonne had said was to indicate the "best bar."

Sidi ben Baar had sighted it too. He breathed an order, like one who sights a sacred object.

The bar with the crescent upon it was laid reverently on the sand, with the sign uppermost.

Then, to the cousins' astonishment, the Sidi and all his followers fell to the ground on their knees and bowed reverently before it.

The salt bar was then borne to the gilded palanquin, wherein it was placed with great care, all the worshippers following in the bearer's wake.

A white horse was brought forward for the Sidi to mount.

"Your signature?" demanded the business-like Henri, holding out his note-book for the Sidi to sign.

The fierce leader seemed tamed, and gently brushed the note-book aside. He thrust his hand into the folds of his white robe. He brought forth a resplendent manuscript in Arabic lettering, as Tony took it to be.

"Take back this letter to Gaston Jambonne as swiftly as may be, O worthy Frenchman, and if any ask thee the price of capsicums, answer them that capsicums will be on the market by March the Eighth. Repeat those words, Henri Leprince," commanded the Sidi ben Baar.

The fierce black eyes compelled response. "Capsicums will be on the market by March the Eighth," Henri repeated like a child echoing its teacher. "Is there no merchandise to take back, O Sidi ben Baar?" he queried after a pause.

"Nought but yourselves, roumis, and the message I have now delivered to you." And, putting his horse to the gallop, the mysterious Sidi followed the palanquin which was being borne at a run towards the city, the Tuaregs following after.

"Salt doesn't seem to be in such terrific demand after all," remarked Tony, ruefully regarding the salt bars lying discarded on the ground.

Henri heaved a great sigh, and his eyes wandered wonderingly to the rumble, empty except for the one remaining bar that had not been removed when once the symbol of the crescent had been revealed on the last bar but one.

Aa, however, seemed to regard the remaining bar as the last stone to his salt throne, for he seated himself thereon and sent his shrill, fivefold whistle echoing over the desert at regular intervals.

No living person was near the trio who, a few minutes before, had been the centre of a jostling crowd of men and horses. They might have been lost in the desert but for the twinkling lights that were springing up in the centuries-old city in the background.

"Rather a different reception to what I had expected," Henri said gloomily. "Hullo! What's the next move in this mysterious mission of ours?"

Aa had leapt to the sand and was uttering shrill cries.

An identical cry, if deeper in tone, answered him from out the darkness.

The thud of hoofs drew momentarily nearer.

Aa's eyes burned like living coals, whilst the unwinking eyes of the Crimson Caterpillar shone weirdly on the distant mud walls of Timbuctoo.

Two strange horsemen in the Tuareg dress bore down on the Crimson Caterpillar to the welcoming cries of Aa.

The horsemen drew rein, and even as they sprung to earth Aa's arms were about the elder of the two strangers' knees.

The strangers barked certain queries in an unknown tongue, and Aa made swift reply, pointing to the one remaining salt bar in the rumble.

The two strangers nodded vehemently, and acted as if there were much to be done—and done quickly!

One of the two stepped up to Henri, whilst the other hoisted Aa back into the rumble, talking rapidly.

"The death of yourself and your cousin is certain," was the startling information flung at the young Frenchman's head in broken French. "You must flee at once."

To which Henri made reply: "Who are you, sir? What credentials do you present? Are you of the House Jambonne?"

In reply the Tuareg spat in the sand as Aa had done at the mention of the Algerian's name. "Escape while you may," he said.

"It is possible to put ourselves under the protection of the French Commandant of Timbuctoo," Henri said calmly.

"Your cousin and yourself will not reach the Commandant alive. Between you and the city is a pavilion where the palanquin will halt, and there your deaths will be decreed, and within a few moments your murderers will be on their way hither." The eyes of the speaker gleamed with a catlike brilliancy in the darkness, and he pointed to his companion who, with Aa, was turning over the salt bar on which the small boy had been sitting so tightly.

Tony had followed at Aa's beckoning. The English boy saw that the salt bar was the focus of interest.

On the reversed surface was inscribed a rough crescent.

Tony whistled. "Henri, come quickly, the Sidi may not have taken the best bar after all!"


CHAPTER XIII
THE UNCLES OF AA

THE salt bar at which the cousins stared was the one that the Algerian Jambonne had inscribed with the secret sign of the crescent, and on another salt bar Aa had duplicated the sign; it was the latter bar that Sidi ben Baar had borne off. Such was the explanation rapidly given in bad French by the two Tuaregs.

"Fly at once," the first stranger cried, and knelt in the sand with uplifted hands.

Alongside of him knelt the second stranger, making the sign of the Cross.

Aa joined the two suppliants.

A triple entreaty!

"I won't bolt," asserted Henri, "till I have discovered the explanation of all this mystery and mummery."

"You will discover only death," answered one of the Tuaregs, whilst Aa said something that probably meant the same.

But the small grey boy did not stop at entreaty, he sprang to his feet, ran to Tony's side, and with tears trickling down his face tried with his puny strength to push the English boy into the driving seat of the car.

The two Tuaregs stood. "You will go," they said, standing one on each side of the French youth.

Henri whipped out his revolver to brandish it before the two apparently unarmed strangers.

"I go to Timbuctoo," he cried obstinately.

"You will go as Tuareg then," cried one, unwinding his litham and flinging off his robe.

Unsupported by any weapon, there was yet something compelling in the earnestness of Aa's confederates.

Henri flung aside his solar topee and his coat. Then flung about him the robe of the Tuareg and his litham. Henri's colour would not betray him, for the two Tuaregs were almost as white as Henri himself; besides, the veil of the Tuareg hid all but a narrow slit of face.

"I will stay and solve the mystery, Tony, my brave one," the French youth cried as he sprang into the saddle ridden a few minutes before by the man whose clothes he wore. "Escape in the Crimson Caterpillar to Bourem with this half-dressed friend of Aa, whilst the other one keeps company with me, as he seems anxious to do. Au 'voir, mon vieux."

Tony sprang to the driving seat, for the hoofs of the murderers' horses could be heard pounding the sand. The half-clothed Tuareg seated himself alongside the English boy. Aa was seated already on the salt bar in the rumble.

There came the thunder of hoofs close at hand. Sidi ben Baar had discovered the trick played upon him, and had come to find the authentic bar with the sign of the crescent inscribed by Gaston Jambonne himself, or to exact the penalty of death on the roumis for their supposed treachery.

Back to the desert once more raced the Crimson Caterpillar, her headlights dimmed that she might elude possible pursuit. At first Tony kept to the trackway to Bourem, but soon his companion urged him to turn aside and follow a course that he would indicate.

Meantime the Tuaregs and Arabs of Sidi ben Baar's following arrived at a gallop to find the salt bars they had flung aside being scrutinised by two stranger Tuaregs—as they seemed to be.

Sidi ben Baar shouted threats at all and sundry, not forgetting a specially deadly curse upon the departed fire-car of the roumis. He sprang from his saddle to go on his knees and hands to examine afresh the salt bars lying on the sand.

"The Sign! The Sign!—where is it?" he screamed in great rage.

"The Sign? The Sign?" queried one and another, stooping over the discarded salt bars.

"The Sign of the Crescent! Where is it?" cried the stranger in Henri's company.

Whilst Henri himself, bending low over the bars, feverishly reversed one after the other, murmuring, "The Sign! The Sign!! The Sign!!!" in the Tuareg dialect.

"Are all the bars here?" screamed Sidi ben Baar, purple with rage and bending, trembling with agitation because no crescent-marked salt had been found.

One of the Sidi's followers recalled that a bar had been left in the car.

"That is the 'best bar' for a certainty," shouted the infuriated Sidi. "And scruple not to kill both roumis if they resist."

The Sidi could not ride as fast as some of his followers, nor any of them as fast as Henri and his companion on their fleet Arabs. So it was Henri and the stranger Tuareg who led the pursuit of the Crimson Caterpillar.

The French youth had no very definite plan, but he was determined that, if need be, he would stand between the pursuers and Tony—not to mention "ma chère Caterpillar!"

But the car had a safe start, and the Crimson Caterpillar was at her best that night. Of that wild journey through the dark, traversing bush country, avoiding straggling thorn trees and low, dense scrub, Tony had but a nightmarish realisation. A dozen times he escaped disaster by inches, but ever the compelling individual at his elbow urged him on.

The thudding of hoofs in their rear grew more and more indistinct. Henri and his companion had misled the pursuers purposely.

When Sidi ben Baar galloped up he found his followers casting round but finding no trace of the escaping car. He marked the two strangers, and little recked that one of them was the very Henri Leprince whose death he had decreed.

"Drive off those two stranger Tuaregs," he screamed. "Not yet would we publish to all the world our purposes."

Henri's companion bowed. "We go, O Sidi," he said quietly; "but it is sad that true believers are not needed till the time is ripe." His compelling eyes focused on Henri for a second.

The two of them rode swiftly off back in the direction of Timbuctoo.

"Follow them and report to me," said Sidi ben Baar to his most trusted spy.

Thinking themselves clear of the Sidi and his followers, Henri and his companion reduced their progress to a trot.

"The car will escape," said the stranger Tuareg to Henri. "My brother Yacoob knows the way, and will take your cousin and Aa to the Secret City where all the Tuareg of the desert will not find them."

And that was the first mention made to Henri of that strange city that no European had yet set eyes upon, of that Secret City to which the cousins were to come. But not yet!

"I go to Timbuctoo if you think we can be sure of the safety of the Crimson Caterpillar and those she carries," Henri declared. "But tell me, friend, why does Sidi ben Baar so highly value that salt bar?"

"Then you did not know! It was as Amadhou declared: you have been dupes of that thrice-cursed Jambonne," said Henri's companion. "It was my nephew Aa that detected the salt bar that would have set the desert aflame. Yacoob and I, Esaf, were at this end to thwart the evil plan of wicked men, and—the night is very beautiful, my brother."

Henri turned to see that a stranger had drawn alongside them—dressed as a Tuareg like themselves.

"Fellow-travellers," said the newcomer in Tuareg tongue, "do you also ride with Sidi ben Baar?"

"Even now we have come from the company of that prophet," Esaf answered. "We haste to the city on important business, not unconnected with Sidi ben Baar, and we must not stay to gossip." He put spurs to his horse, Henri following.

But the Tuareg spy of the Sidi was also well mounted.

It was not very long before the lights of the city loomed up before Henri, and soon he was nearing the narrow gate. It was so different an entry to what he had pictured, and Henri felt sorry for himself and looked down with disfavour on his Tuareg robe. Instead of steering the Crimson Caterpillar in triumph through an admiring crowd, he drew up his horse to his haunches as a French private barred the headlong progress of the two Arab steeds.

"Why so great haste, my chickens?" the soldier demanded, barring the way with an extended rifle. "Is this the way for nomads to force their attentions on the Mother City of the Desert? 'Tis disrespect to our great Republic, that it is!"

"But did you not yourself, only an hour ago, permit us to go forth, O honourable sentry?" queried Esaf quietly. "It is high time we return to our family."

The sentry waved his rifle, indicating the ring of camp fires without the city where the Tuareg were herding their cattle and goats. The lowing and bleating came plainly to the listeners' ears.

"Your family are on the plain, you truants; you come to take the pleasures of our city. Is there not a religious festival on yonder plain where you would be better employed? Many of the Tuaregs have gone in and out of yonder pavilion, there is a certain Sidi conducting a mission, I'm told."

"We have business of great import in the city," said Esaf to the garrulous sentry, and his grave manner impressed the sentry as it had done Henri himself at the first meeting.

"Pass, Tuaregs, pass," said the sentry. Which shows how complete was Henri's disguise.

"And now whither?" Henri asked. "Shall I go and complain of the Sidi's behaviour to the French Commandant?"

"What will you tell him, friend?" questioned Esaf. "It may be that you have committed a crime against the Republic, and may find yourself in prison. I do not think you are aware of the affair in which you are involved. To tell the truth, I fear that fellow who spoke to us just now outside the city was a spy."

"We are surrounded by as strange a crowd as ever I saw," said Henri, looking about him.

In the Place Joffre there were samples of most of the races of Savage Africa. From the veiled Tuareg of Ayer to the hooded Arab of Tunis, from the fuzzy-haired native of the Soudan to the shaven-headed labourer of Ashanti, from the barbaric elegance of the Timbuctoo lady to the primitive simplicity of her Haussa slave, from the Fulah countryman on his leisurely ox to the Chaamba courier on his cantering steed, from the Moroccan Kaid riding his slow-pacing dromedary to the half-caste negress squatting on a mat selling sweetmeats.

To Henri's ears, above the hubbub of conversation and the rumble of traffic, came the dull beating of drums, the strident notes of a Tuareg stringed instrument.

Henri's senses were confused by the strange sounds and sights about him, so that was why he did not note a Tuareg horseman who drew close and, using the pressure of traffic as an excuse, lurched against him.

There was a swift movement at Henri's breast, and his Tuareg disguise was torn aside.

Henri cried out to Esaf that a pickpocket had attacked him. But before Esaf could turn his horse round and come to the French youth's assistance, the strange Tuareg had incorporated himself with the crowd and disappeared.

Out through the city gates galloped a Tuareg spy a few minutes later, spite of the bayonet of the French sentry extended ten seconds too late to stay the rider.

So it came to the ears of Sidi ben Baar, seeking the trail of the Crimson Caterpillar, that beneath the dress of one of the stranger Tuaregs he had driven from the salt bars were the garments of a white man—those of the treacherous agent of Gaston Jambonne.

"See that he die," said that relentless leader. And four Tuaregs were deputed to carry out the murder forthwith.


CHAPTER XIV
THE BAR OF SALT

"WHITHER do we drive?" Tony asked wearily as the Crimson Caterpillar careered onward towards the sunrise.

"To the safety of the Secret City," Yacoob replied, and, making the fourfold finger touch upon his breast, he added reverently: "By the Sign I conjure thee not to stay your flight."

"But my cousin—he will never find us," protested Tony. "Even now he may be fighting for his life in Timbuctoo against the mysterious foes that are springing up on every side."

"Your cousin is in my brother Esaf's hands, O white stranger who hast been good to Aa, so fear not," pleaded Yacoob. "In due time when the business in Timbuctoo is concluded, we shall all meet in the Secret City. . . . Onward! lest our enemies on swift meharis, or by the message of the drums to desert watchers, entrap us before the city be reached. Onward!"

"Onward!" echoed Aa from the rumble, imitating his uncle's urgent word.

As the pink glow of mom lit the wilderness of the sand dunes Tony drove on, hearing in imagination the thud of pursuing hoofs, the shouts of camelmen thirsting for his blood. He wrenched every ounce of power out of his engines, driving onward till he drooped from sheer fatigue.

The compelling eyes of the strange Tuareg at his side, however, kept urging on the English boy, even after Tony's physical strength had ebbed away.

Lower and lower, eyes strained to pick the path over the dunes, Tony slumped over the steering wheel. And dropped asleep athwart it.

The Crimson Caterpillar came to a standstill.

Yacoob called to Aa, and together the two, uncle and nephew, helped the semi-conscious English boy to a resting place in the shade of the car on the sand itself. They gave him a drink of water, which he drank feverishly before falling into the dead sleep of exhaustion.

Tony awoke in a truculent mood. The sun was high in the heavens. What folly had he committed in thus running away at the word of a mere stranger? Why had he left Henri to face the fury of Sidi ben Baar? What a dreadful funk he, Tony Mase, must be to do this mad thing! Yet—yet that murderous band of the Sidi's, waving aloft rifles and spears, shouting vengeance, certainly had been an incentive to flight. Nevertheless now that he could think clearly, Tony felt that duty called him to return to Timbuctoo.

Aa and his uncle were completing preparations for a meal.

"We go back to find my cousin Henri after we have eaten," Tony barked as Yacoob bent to hand him a cup of coffee.

"We break our fast," said Yacoob quietly. "The heat is very great."

All three were glad to recline and enjoy their meal in the shade of the car, Aa nestling gravely alongside Tony.

"When the sun starts to descend the sky," said Yacoob presently, "we resume our journey."

"—To Timbuctoo," said Tony firmly.

"—To the Secret City," responded Yacoob not a whit less resolutely.

"I insist that we return to Timbuctoo," Tony cried.

"Then you disobey your cousin's command," said Yacoob gravely.

"He told me to go to Bourem."

"Were we within a mile of Bourem at this moment, we should be lifeless—corpses left in the sand by raiders whom France would strive in vain to bring to justice. If you insist on driving us back to Timbuctoo, you take us and yourself to a bloody desert death, and you set free the hounds of war in the Sahara. And Algiers herself shall hear the baying of the dogs at her very gate."

"O dry up your drivel, Yacoob!" cried an exasperated young Englishman. "If you can't explain all this mysterious tommy-rot about a salt bar, we park in Timbuctoo to-morrow."

"There lies the reason," and Yacoob indicated the salt bar in the rumble whereon Aa sat.

"A bar of salt!" exclaimed Tony irritably. "What of it?"

"Amadhou commanded that it should be brought to the Secret City," Yacoob said.

"Who is Amadhou? And why did he command it?"

"Amadhou commanded that the bar of salt marked with a crescent should not be allowed to reach Sidi ben Baar," responded Yacoob. "And his command has been obeyed by the High Priest's son himself."

"Not quite so fast," implored Tony. "I'm getting dithered. As far as I can follow, the salt bar is the centre of the mystery. Gaston Jambonne, a trader of Algiers, marks it with his sign manual; a Frenchman with a crooked nose is mightily interested and gets nearly killed for his interest; French officers, a leprous marabout, Tuaregs with weapons, Tuaregs without weapons, Sidi ben Baar and his Arabs and Tuaregs, your Amadhou—whoever he may be!—all struggle for that bar of salt. And we have it! But what's the import of it? Why all this bother about a salt bar? Tell me, who is Amadhou? And who is the High Priest's son?"

"Amadhou is the blind physician who is the guide of our race," responded Yacoob. "Even now your cousin and my brother are probably dwelling in his house in Timbuctoo. Amadhou is so blind that he sees more than mortal eyes can see, and sends his messages to our Secret City and out over the desert without the aid of wires. A man more than mortal is Amadhou, who walks in the gardens of magic."

"Amadhou is, apparently, the Secret City's wireless operator in Timbuctoo," commented Tony. "As to the command that has been obeyed by the High Priest's son, who is the High Priest's son?"

"He sits beside you," responded Yacoob.

Startled, Tony turned to gaze on Aa, on the solemn little face looking with unwinking eyes across the immensity of the desert. "So Aa is the High Priest's son. From the moment he came to the Crimson Caterpillar during the sirocco, sent there by Amadhou's orders, perhaps by Amadhou's servants, he has been exploring amongst the baggage to unearth that special salt bar, which, when found, he intrigued how he might keep it from Sidi ben Baar; and, by duplicating the mark on another bar, has left us with the doubtful blessing. What is to be done with this fateful bar of salt?"

"It goes to the High Priest," responded Yacoob, "to the temple and the city beneath the sand."

"So your Secret City is subterranean, Yacoob?"

"Partly above and partly beneath."

"Yet why all this intriguing," asked Tony, "when at any time the Tuareg warriors might have taken the salt bar from us by force?"

"We Grey Tuaregs use no force, and employ no weapons," responded Yacoob.

"But the Tuaregs who came upon us in the night at the Black Goblin Eyrie were triply armed, and—"

"They were not Grey Tuaregs, white stranger, they were the raiding Tuaregs of the desert who believed you were agents of Jambonne, the enemies of our Faith, whom Amadhou, at the prayer of the High Priest, would fain circumvent. We of the Secret City of Ichaf have ever warred against war, being followers of the prophet who left us his Sacred Sign." Yacoob reverently made the Sign of the Cross on his breast. "We of the Cross would thwart the followers of the Crescent who would bring red war to the Sahara. In Algiers we have our watcher who tells Amadhou all that the evil Jambonne plans."

"Why should I not go and tell Henri my cousin all this?" Tony asked.

"Because my brother Esaf will have already done so," replied Yacoob, "and because between you and the city of Timbuctoo lies the vengeful force of Sidi ben Baar, and not even the power of France could save you from the Sidi's revenge."

"Humph!" said Tony, recovering his spirits. "It looks as if Henri and I have a coconut to crack between our teeth. Do you swear that Esaf will bring Henri to the Secret City, Yacoob?"

Yacoob hesitated. "Undoubtedly," he said, and Tony failed to note the hesitation.

"How far off is this Secret City of yours?"

"Two or three days' journey by mehari, white stranger. Yet, on the fire-car it may be—"

"A few hours' run," Tony said calmly and climbed to the driver's seat.

The few hours' run, however, proved to be a trying journey of many, many hours. Up one mound of sand and down another till Tony wondered how the caterpillars of the car could stand the strain. He shivered as he thought how dreadful would be his predicament, without Henri's expert knowledge, if the Crimson Caterpillar broke down here in this labyrinth of jaundiced sandhills, amongst these ominous billows of sand, shale and gravel which seemed to be rolling down on the car as she sped on under Yacoob's direction.

At top gear Tony sought to plough through the clogging sand and grit till the water in his radiator boiled, and he was forced to halt and supply more of the precious water, the stock of which was running low.

In the late afternoon came the first change in the monotonous landscape. The Crimson Caterpillar ran by her own weight into a huge basin surrounded by dunes of sand. Instead of sand there was a slate-like surface which threatened to rip the tyres to shreds.

At sundown Tony found himself climbing out of the basin to the sand dunes, but before the car could climb further it was necessary to supply more petrol. Also the human beings were in need of revictualling, but water was denied them by Tony's urgent appeal; he reserved the last pint for the Crimson Caterpillar.

"Unless we reach wells within an hour," he said, "the car is useless."

"The Secret City is at hand," said Yacoob, without much conviction.

Tony climbed one of the highest sandhills, using his binoculars in an attempt to sight a haven. But so far as the binoculars enabled him to see there was only a wilderness of sand. And night was fast descending over the desert.


CHAPTER XV
THE SACRED CITY OF THE SAND DUNES

THE last glimmer of light had faded from the sky. The headlights alone enabled the Crimson Caterpillar to proceed.

"We are lost," cried Tony, bringing the car to a standstill.

"We are even now close to the Secret City," said Yacoob.

As if Aa were aware of the same fact, that small youth had leapt out from the rumble, running off into the darkness.

The Grey Tuareg leapt to the desert sand. Shouting: "Follow, white stranger," he ran after Aa.

With one despairing glance at the Crimson Caterpillar, Tony rushed after Yacoob, fearing to lose him in the darkness.

The English boy cannoned into the Tuareg, and together they trudged upward over a sand dune.

"See! There is the Secret City of Ichaf," cried Yacoob.

Tony's eyes, however, could not penetrate the darkness; he could only stumble on after his guide. Down in a deep depression they went, and the Englishman must needs fumble with his hands to maintain communication with Yacoob.

Tony tripped. His head encountered something solid and hard.

"Are you blind, white stranger?" Yacoob asked, wondering. He himself possessed the power common to all Grey Tuaregs of seeing in the dark. Generations of underground life had developed that catlike quality in the Grey Tuareg.

Tony was stunned, and stammered out: "What have I hit?"

"The city wall," responded Yacoob, lifting him.

The Tuareg had been skirting the city wall, looking for the one narrow entry in the outer battlement of Ichaf. Aa's hail told them they had reached their objective.

Through a hole that scarcely gave room for a grown man to pass the two crawled to find Aa on the other side.

The trio traversed a broad, dry ditch, to come to a second line of high black wall like the first. It was unscaleable and hard as cement.

Again they skirted the wall till a second hole like the first was reached. Yacoob and Aa were as certain of the way as if it were floodlighted, but to Tony it was all utter darkness.

"Have a care, white stranger, seeing you are blind o'nights," cautioned Yacoob.

On the inner side of the second wall Tony's feet encountered steps leading downward.

Cellar deep the city lay, protected by its circle of double ramparts and deep moat. Ichaf was a rabbit warren of narrow lanes and barricaded dens. By labyrinthine alleys Aa led unhesitatingly; nowhere was there room for two to walk abreast. Tony merely clung to Yacoob's shirt and passed through narrow slits of streets bordered by high black walls. Rats scampered across his feet. Now and again he was aware, through the medium of touch, of stout, wooden doors, barred and locked.

To one such door they presently came. Yacoob produced a key. There was the sound of a lock turning, and then Tony found himself stumbling on again in darkness that was profound, clinging to Yacoob. On the morrow Tony was to learn that each house was a series of dens, each with its palm-plank door, each barred and bolted.

Through an ant's nest of compartments they passed till at length a final door was reached, and Yacoob unlocked it to reveal a tiny courtyard with a patch of sky in lieu of roof. But even now, as throughout the weird progress on foot, no single human being appeared to be inhabiting the city.

"It is here I thought best you should rest till the High Priest decrees his will," said Yacoob. He pointed to an outside stairway leading to a roof.

The moon was rising from out the desert, and, stumbling up the steps, Tony looked forth on one of the strangest sights a European might see—a city built entirely of salt. The salt was set as hard as the hardest concrete, and was black with the filth of ages. Rain seldom visited Ichaf, perhaps thrice in a citizen's lifetime, and the rest of his lifetime the sun was at work petrifying the salt into indestructible stone. This much Yacoob told the weary Tony.

After one tired glance round on all that mysterious city that lay above ground, Tony asked to be shown the Crimson Caterpillar.

"She is there, behind those twin hillocks of sand," Yacoob said. "Aa has gone to his father to enquire his will concerning the fire-car."

"Don't let them harm her," Tony begged, and then lurched sideways into Yacoob's arms.

On a bare bench of solid salt Yacoob laid the exhausted boy, flung over him a rug, and left Tony to sleep as soundly as if he were in his mother's house in Algiers.

It was high noon when he awoke. Yacoob had erected an awning over the bench of salt to temper the rays of the flaming sun.

A lump of dried dates and an earthenware cup of luke-warm water was Tony's breakfast.

"There will be meat from the tin and biscuits from the car for your lunch," declared Yacoob, as he stood looking down in kindly fashion on the English boy. "Aa is fetching such delicacies from your fire-car, white stranger; we who live in Ichaf content ourselves with dates and water chiefly."

"While we are on the subject of water," Tony chaffed, "where is the bath room?"

"We will visit the bath pool after you have broken fast," Yacoob replied.

As he munched his dates and washed them down with the tepid water, Tony looked out over the Secret City of Ichaf. Here and there on low roof tops he saw signs of life: a woman spreading robes to dry in the sun, a child tethered to a post crawling in a circle, and high up in the heavens a couple of carrion vultures—the natural scavengers of Ichaf. Beyond the unbroken circumference of the walls of the city of salt, for the two crawling holes were not visible, Tony saw a grove of date palms, watered, as Yacoob told him, by a subterranean river, on which Ichaf depended for very existence.

Blocking every horizon was sand, sand, nothing but a wilderness, out of which Tony wondered if he would ever escape.

But he fought his fears and turned his thoughts to the landscape. "What are those pits yonder where bare-limbed men wade and draw up something in shallow scoops, Yacoob?"

"Those are the salt workings," explained the Tuareg. "There all Ichaf finds its living, making the salt cones which are fetched by caravan monthly. The traders wait on their camels in the desert, a league from the Secret City, bringing food supplies and clothing for the much-desired salt. To those same salt pools I will take thee, white stranger, to have your bath."

"But what about the Crimson Caterpillar—is she safe?"

"The High Priest has set a ban upon her, and no one dare touch the fire-car, unless he have permission from yourself," Yacoob explained.

Which explanation brought forth a volley of questions from Tony, all of which Yacoob parried. One fact only was made quite clear, the High Priest was the brother of Yacoob and Esaf, and the father of Aa.

Tony, however, was insistent. "Where is the church?—the mosque?—the temple?—or whatever you term it? What is your religion, Yacoob?"

Yacoob made the Sign of the Cross. "It is an older faith than that of Mahomed. Our religion is that of Christos Who came from Allah and told men to love and not to fight."

"That is my religion," cried Tony wondering, and staring at the Grey Tuareg wearing the customary litham and robe of the desert men. "We are both Christians."

Yacoob shook his head. "The white stranger's religion may be a good one, but it cannot be the religion of Christos Whom we Grey Tuaregs worship. Christos came to bring peace on earth and to tell men to cease from killing other men. But the white strangers, whom I have seen in Timbuctoo and Algiers, all you roumis, fight even as Mussulmen fight. Do you not yourself, O white youth, wear a killing tube in your belt?" And Yacoob pointed to the revolver at Tony's side.

"But—but—" Tony did not know what to say; he didn't claim to be a saint, but, hang it all! the man of the desert had a cheek to say that he—Anthony Mase—was no Christian! "Tell me," said Tony in triumph, "don't you defend your city of Ichaf if raiders come?"

"Seldom do the Mussulmen Tuaregs violate the Secret City, nor would they find within much to make a raid worth while," replied Yacoob. "Yet if raiders come to Ichaf, we do not resist them. We follow the commandments of Christos Who said if a man take away thy litham, thou shouldst let him have thy robe also, and if a man smite thee on the right brow, thou shouldst let him smite thee on the left also."

"But your holy book, Yacoob, does it forbid you to fight?" asked Tony, amazed; there seemed something familiar in the words Yacoob had used. "Would you not resist a raider?"

"The Grey Tuaregs have no holy books, only the words that come down through our High Priests, father to son. They tell us that in the Days of Peace that are to come the lamb and the lion shall lie down together, and the spear shall be beaten into pruning hooks for harvesting the dates all the world over."

Tony could only stare and recall Scripture lessons at school. Yacoob was repeating words similar to those Tony had learned in the Bible. "But—but, Yacoob, why do you think I am no follower of Christos?"

"No follower of Christos may murder his brother man, even though he murder ten at a time with a shot-machine and call it war. Nor may a Grey Tuareg who is a follower of this Christos go forth to raid the Tuaregs who follow Mahomed, or like the roumis who bring armies to wage war, O young white stranger."

Tony was bewildered. "But we roumis, as you call the foreigners, are Christians, followers of Him you call Christos!" the English boy protested.

Yacoob smiled condescendingly, pointed to Tony's revolver, and shook his head. "If you roumis followed Christos, you would have built for yourselves cities which needed no weapons to defend them, like our Secret City of Ichaf. And you could not bring armies of raiders to kill other men if you followed our Christos, O very young white stranger."

"I think I'll have that bathe you talked about," said Tony. "I shan't get out of my depth in the brine bath as I do now in conversation."

Yacoob smiled in kindly fashion on the heathen boy—for so he considered Tony to be!—then, pointing to the environs of Ichaf, turned to the steps that led from the roof.

Down into an eerie gloom, by closed doors which had to be unlocked after spying through tiny holes no bigger than a penny, on through a rabbit warren of rooms to a narrow lane they went.

At that time of day the sun shone in shafts on the twisting, wall-bound alleys that seemed to Tony to be endless. But at length they came to the crawling hole through which they had entered the city the night before.

Tony found himself outside the frowning black walls of Ichaf. "Can this moat be filled with water?" he asked, pointing to the broad depression between the two lines of blackened parapets.

"Unless El Bahr* were turned this way there would be no water sufficient to fill the moat about our city," Yacoob said. "Yet it may be that, before the sand overwhelmed the Sahara, there was here a fertile country with much water. The Ancient Ones who built our Secret City may well have defended Ichaf with a ring of water, since they might not defend her with murderers' tools. It is certain that this great dry moat now forms no defence against raiders, for when the raiders came with the caravan seventy moons ago they entered the Secret City in the same way as you entered it last night, white stranger."

(* The Niger)

"Did they plunder Ichaf? Was no one killed, Yacoob?"

"They found no single living being within the city, save only three old women and two bedridden men, and they found no booty worth the carrying away. There were three men killed, for the raiders came at night, and in the darkness of the narrow lanes they grew confused, and spearmen killed spearmen, mistaking their fellow-raider for enemies in their fear and bewilderment. Always Ichaf has borne the reputation of being bewitched, and our raiders went away certain of it, saying the inhabitants had taken the form of rats and moths and insects—to return to human form when danger was past."

"But where were the inhabitants of Ichaf hidden?" asked Tony.

"In the city beneath the sand," replied the Grey Tuareg.


CHAPTER XVI
THE BLIND PHYSICIAN AMADHOU

ESAF was much alarmed when Henri cried out that a pickpocket had attacked him. The Tuareg closely enquired what had occurred.

"He desired not your money," Esaf groaned. "He was no doubt a creature of Sidi ben Baar, seeking a chart or desiring to penetrate your disguise. Doubtless he is now galloping across the desert to the Sidi who will send back murderers to make an end of you."

"How very interesting!" remarked Henri ironically. "What do you suggest? Shall I go at once and claim the protection of my country at the palace of the governor?"

Esaf considered, as the horses paced slowly through the throng of the street. "It may be you have brought trouble to Timbuctoo, Capitaine Leprince, for which the commandant may award close imprisonment till explanations be given. And the High Priest of our Secret City desires the salt bar to be taken there, not that it should fall into the hands of France. There is more in this matter than you even guess."

Henri grew irritable. "By the Tower Eiffel! How can it be that I have brought trouble seeing it was salt the Crimson Caterpillar brought to the Soudan!"

"I see but darkly," responded Esaf, "but Amadhou, the blind physician, perceives all things.... Yet hush! there are spies about us; speak not on private matters as we ride."

Growing more and more impatient, Henri racked his brains for the true explanation of all this mystery and plotting, and rode with tight lips after Esaf.

Across a Place that reminded the Frenchman of Algiers, by strange streets bordered by mud hovels and crenellated walls that reminded him of Old Cairo, the two steeds carried the strangers. To the black folk who stepped aside to let the horses pass, Henri and Esaf were members of that desert aristocracy the Tuareg.

Presently Esaf reached a square upon which frowned down a strange erection of grey mud walls with a curious squat minaret decorated with dead branches. Henri asked whether it was a fort.

"Nay, 'tis a mosque of the Mussulmen," answered Esaf, "the Mosque Djameh Sankoreth first built ages ago. Within its shadow is that which I seek—the dwelling of Amadhou. There we may find sanctuary lest Sidi ben Baar cut our throats."

"But why should the Sidi desire to let out our lives through our throats, Esaf, for have I not brought the salt he wanted?"

"The salt bar that the Sidi wanted is now on its way to the Secret City with my brother Yacoob and thy cousin, Capitaine Leprince," explained Esaf. "Hush! Follow swiftly, asking no question."

Passing close under the walls of the ancient mosque, the two steeds cantered cautiously, and suddenly Esaf's steed swerved sharp right, to pick its way down a narrow lane till it reached a doorway set in a high mud wall.

Five times in quick succession Esaf tapped the lintel.

From a narrow grille above the door a face looked forth—a sallow face with yellowish eyes that gleamed in the dark.

Followed an interchange of sentences in a tongue unknown to Henri.

It was nearly three minutes before the door cautiously opened, and the sallow-faced youth ran forth to gather the bridles of the horses in his hand and disappear in the darkness with the steeds.

Swiftly Esaf entered, followed by Henri.

And though Henri saw no one, nor heard anyone except themselves move in the shadows, he half-expected a dagger to sheath itself in his back, so swift and sinister had been their entry. For the door crashed suddenly behind them.

Though it was pitch dark for Henri, Esaf evidently found no difficulty, taking Henri's hand and leading him along what might have been a subterranean tunnel, for it sloped steeply down and then trended upward again.

Esaf halted. There was a fivefold knock on wooden panels. A door swung open before the visitors.

When Henri's eyes had adjusted themselves to the gloomy interior, lit by wicks floating in earth-nut oil, he saw how uncanny was his place of refuge.

Every inch of the apartment was crammed with articles which the curator of a museum might have coveted. A stuffed crocodile was suspended from the ceiling, which was decorated with cabalistic signs, circles and crosses and small fish. A mummy in its case seemed to be leering from one corner at a skeleton hung on a gibbet in the opposite corner. There was a big table with a marble top and legs of petrified mud fashioned like snakes, and every inch of its surface was crowded with mysterious flasks and cabinets of scented wood. A long stone coffin occupied one side of the compartment, and heaped in it were things that made Henri's spine creep. There were human bones on which a skull stood grinning, bats mounted on small boards, skins of lizards shrivelled and dried, horrible things preserved in bottles, instruments that might have belonged to surgeon, dentist or torturer, rusty fetters of massive make, and what Henri took to be an executioner's block, for a great two-handled sword lay atop it.

But the creature who sat high up, cross-legged, on a huge stool, dominating all, was the uncanniest exhibit there, Henri thought. The man was of massive proportions, skin of whitish-grey and eyes of yellow that flickered ceaselessly in their sightless sockets. A living snake of vivid green was wreathed about his bare shoulders, and a black tail-less cat sat at the base of his stool. He wore a lion-skin about his middle and a round black cap upon his white hair.

"I feel you are a good man, O youth of the roumis," said this strange being in perfectly enunciated French; then, turning to Esaf, spoke in another tongue.

At the first pause Esaf turned to Henri. "Physician Amadhou is blind but he sees you are meditating no evil. He therefore takes us under his direction and will counsel us what to do. We may rest in this room for the night."

"In the stone coffin?" queried Henri, meaning his remark for a joke.

"In the stone coffin," echoed Esaf gravely. "There is room for both when we have removed the contents. Here alone in all Timbuctoo we may sleep soundly, for no man, even if he knew how to come hither, would have the hardihood to face Amadhou the magician, who is the Timbuctoo adviser of the Secret City, where he was born, and which he ever loves."

"Doctor Amadhou is the acting Consul for your Secret City here in the capital city of savage Africa?" Henri enquired.

"That may or may not be, Capitaine Leprince," Esaf replied; "but there is no man in the Sahara or the Soudan equal to Physician Amadhou who works magic."

Henri nodded and felt suddenly tired, as if the musky smell of the uncanny room were drugging him. "I must lie down," he murmured.

The Frenchman had leaned back against a great war drum decorated with the horns of goats, and his eyes had closed.

Swiftly Esaf, helped by Amadhou, cleared the stone coffin of its queer contents. The blind giant seemed as though possessed of all his faculties, and laid goat-skins in the coffin whereon the sleepers might lie.

Henri awoke next morning to find himself in the stone coffin, wrapped in his Tuareg robe.

Amadhou was seated on his enormous stool, boiling a red fluid in a retort, the vapour distilling drop by drop in a condenser of glass. The tail-less black cat sat upon his shoulders, and she mewed as Henri looked about him.

"You have slept well, Frenchman?" the blind giant asked, slightly inclining his head in Henri's direction.

"I have dreamed somewhat," the French youth responded politely. "Where is Esaf?"

"He was thy bed companion, but has gone forth to gain tidings of those who seek thy life," Amadhou said; then suddenly cried: "Down, Satanas!"

Henri could scarcely repress a yell as the great green snake came rustling in over the edge of the coffin as if he wished to fill the place lately occupied by Esaf.

"Down, Satanas!" commanded Amadhou and whistled shrilly.

The snake lifted its head and swiftly slid over the coffin edge to coil itself at the foot of the stool on which its master Amadhou sat.

"You are hungry, O Frenchman," said Amadhou. "The breaking of your fast is nigh—even at the door."

With which remark the heavy door of the compartment swung open and the sallow-faced youth with the yellow eyes entered, bringing on a platter fish from the Niger. It had been fried in earth-nut oil, and was served with rice cake, followed by a cup of goat's milk.

"Who is this Sidi ben Baar, Doctor Amadhou?" Henri asked, when he had finished his breakfast.

The blind magician was still engrossed with his distillation, but answered at once. "Sidi ben Baar claims to be a holy marabout from the Eastern Soudan where the English rule, and he aspires to do here what the Mahdi did in Khartoum, though I am laughed at when I dare to make the statement. You roumis have no imagination and the followers of Mahomed are prone to be deceived by a pretension to holiness. Wherefore I am a voice crying in the wilderness, as our High Priest says. And almost alone I have to fight the machinations of wicked men. Yet without the salt bar the Sidi cannot succeed."

"What is there so sacred in a salt bar marked with a crescent?" Henri asked.

"That is a matter that I cannot mention," said Amadhou, stirring the snake with his foot. "My twin brother Houama is even now enquiring closely into the matter, and is looking out over the battlements of Ichaf expecting the arrival of Aa."

"How do you know all this?" demanded Henri.

"We communicate with each other," said Amadhou simply. "My mind is attuned with Houama's, and I will enquire even now if your cousin Antonio has arrived at Ichaf."

Henri was amazed. "But this is telepathy—the real brand. I have read of it but never believed it possible."

"It is a very old science, and it is vastly improved upon by the discoveries of you roumis. For it is told me that a man speaks in Paris and a thousand may hear his voice in Algiers. Though Houama speaks from Ichaf to me, it is only I who hear his thoughts."

"But wireless is possible only with delicately adjusted instruments helped by the power of electricity," asserted Henri, "whilst you use no instrument at all, Amadhou."

"I carry the delicately adjusted instrument of my brain," declared Amadhou, "and it is attuned to the instrument of my twin-brother's brain."

"Can you tell me whether my cousin is safe and well?"

"Perchance, though the hour is not one when Houama and I are wont to communicate," responded the man of marvels. "However, if he should be at leisure, I will call him."

Wondering if the man was a charlatan, Henri watched Amadhou blow out his lamp and carefully set still and condenser aside, tossing the cat to the coils of the snake.

The blind magician folded his arms on his bare breast, gathered his lion-skin about him, and set his sightless eyes staring, unwinkingly, eastward.

No single word escaped his tightly compressed lips, but in a few minutes his face lit up as when one friend meets another. He appeared to listen intently, and his head nodded several times.

He turned towards Henri like one awakening from a trance.

"You are there, Frenchman?" he asked.

"Yes, Amadhou, and what news have you of Tony?"

The blind giant might not have heard Henri's remark for all the attention he gave it. "Aa has not yet reached the Secret City with the salt bar," said Amadhou. "But my brother and I think similar pictures; we see three sleeping in the desert under a strange steel tent of crimson colour."

"The Crimson Caterpillar!" exclaimed Henri. "Tony, Aa and Yacoob are resting in the shade of the Crimson Caterpillar."

"A Crimson Caterpillar—how big it must be!" exclaimed Amadhou. "Is it the grub of a day flying or a night-flying insect?"

Henri chuckled: it was refreshing to find that magicians were mortal and might make mistakes. "The Crimson Caterpillar is the name I have given my motor car, Doctor Amadhou."

"Aha!" laughed the giant, opening cavernous jaws to reveal toothless gums. "I sent Aa to solve the secret of the salt bar in the fire-car, but I did not know the roumis called their cars caterpillars. Always there is much to learn, ever on through the ages. I trust my spirit may learn more and more. But this caterpillar of thine—tell me more about it."

"It is a special car built for desert travel, and—"

"Ah! Now I know. The Crimson Caterpillar is a Citröen fire-car fitted with flanges which carry rubber wheels over all obstacles. Not twenty moons ago there came gallant explorers for the first time across the Sahara on such machines, and I went to the Place Joffre and saw them with my hands, as the kindly young French engineers allowed. You roumis are men of magic. That wireless magic which you named; it is marvellous than an untrained child can hear the voice from afar. Houama and I spent many years acquiring the art of giving off and receiving thoughts from afar." Amadhou's face suddenly clouded, his body stiffened. "There is danger in the air," he said.

Amadhou sat still as a statue, only his yellow eyes flickering in their sightless sockets.

Henri was about to speak but made no sound.

"Silence!" hissed the brooding giant. "I am ascertaining whence the danger comes."

There was another period of silence.

"It comes—it comes from—from the desert," droned the blind physician Amadhou. "Death and destruction to all our plans!"


CHAPTER XVII
THE SALT MINES OF THE CITY

IT was a strange group of workers, standing knee deep in brine, that stared as Tony approached on that first morning after his arrival in the Secret City. Not one of the salt-workers had gone further than a mile into the desert that surrounded his home, not one of them had seen a European before.

Yet they gave no extravagant expression of their curiosity as the Englishman, so different in feature and dress, waved a hand in welcome.

The salt workers responded with their customary salutation, a fourfold tapping on their chest, the Sign of the Cross. They wore neither Tuareg veil nor robe as they worked, though they did so at other times. They were stripped except for a loin cloth. Some bore baskets, others what looked like fans.

Tony turned to Yacoob. "Ask them to go on working as if I were not here," he begged. "I want to see how the salt is collected."

Yacoob addressed his fellow-citizens, and at once they divided into groups of three, wading in shallow basins flooded with water of rusty red. Two of each group delved with their fan-like scoops and brought them up piled with glistening salt which had crystallised out of the supersaturated solution in the pool. Both tipped their catch into the basket of the third, who hurried off as another basket-bearer came to take his place.

"They collect the salt mighty quick, Yacoob," Tony remarked, astonished at the procession of basket-bearing workers.

"Where the workers now delve was once the ocean bed, white stranger. We dissolve the adulterated salt in water and add natron to send the sand-mixed salt back into clean crystals, which are now being carried to the moulder, who makes the finished bar or block."

"Please let me see a moulder at work, Yacoob."

They climbed upward from the basin of dissolved salt, over mounds of débris, the outworks of an industry half as old as time, and, reaching a hillock glistening with salt crystals, came suddenly on a group of workers setting the salt in moulds.

The basket-bearers kept running up to tip the wet salt by the moulders' feet.

Mixed with an equal portion of dry crystals, the wet salt was tightly packed in a mould half as high, as the Grey Tuareg who moulded it.

The actual mould was so encrusted with salt externally that Tony could not gather how it had been made, and asked Yacoob for information.

"The mould is made of palm sticks dried in the sun and bound with camel hide to the required shape and size," explained Tony's guide.

The mixed salt was tipped into the mould and the moulder used a wooden ramrod to press the crystals down into shape.

"I have an idea," cried Tony suddenly. "It would he quite easy to introduce something solid into one of the salt shapes. Where is our salt bar, Yacoob, the one we brought across the desert from Timbuctoo?"

"The salt bar marked with the crescent lies at the feet of Padaa, the High Priest, the father of Aa."

"Where is Aa?" Tony asked, and, turning at a slight noise, found Aa at his elbow.

The boy with the creased forehead spoke rapidly to Yacoob who translated.

"Aa says that the magic car is now housed under an awning, and he wishes you to know that your cousin slept in the house of Amadhou, secure from all danger, in the city of Timbuctoo."

Tony scanned the horizon in the direction of the Niger Bend. "You have no telegraph poles and somehow one doesn't expect you to be in wireless communication with Timbuctoo."

"This Secret City of the desert has talked to the great city without any need of wires," responded Yacoob, "as long as man can remember."

"Wonderful!" exclaimed the English boy. "There must have been a desert Marconi before the Marconi whom the Western world knows."

Yacoob nodded vaguely.

Tony's thoughts returned to the salt-workers before him. "What becomes of all these pyramids of salt, Yacoob?"

"At full moon, white stranger, the Tuareg of the Beyond, our brothers who share our secret, come from afar, bringing rice, millet and cotton, and such things as we need from the outside world. In exchange for these necessities we give them the salt. Thus has the Secret City existed through the centuries."

"And through the centuries, you dare to tell me, Yacoob, that the men of Ichaf have never fought?"

"How can they do so, white stranger? No follower of Christos may kill a fellow-man."

"But this religion of yours—whence came it?"

"The High Priests tell us that in distant ages, long ago, there came to this oasis a holy hermit out of Alexandria, the holy city of Egypt. He found here a fear-ridden remnant of the Semitic race who fought desperately against the fierce raiders of the Sahara. The hermit preached to them of Christos Whom the Romans had crucified, and said that those who followed Him must fight no more. So here they built a refuge where men might pray and work, and the hermit married a woman, one of the Semitic race, and their son was our High Priest. Indeed, the descendants of the hermit have been our High Priests down to the present day, and Aa is our High Priest-to-be. It was he alone who could be relied upon to solve the trouble of the salt bars of Jambonne, and our Tuareg of the Beyond brought him to you on the wings of the storm seeking the salt bar which might drench the Sahara in blood."

"But who told you Grey Tuaregs of the salt bar, Yacoob?"

"In all the cities bordering the Sahara, white stranger, we have a citizen of the Secret City, and he—by wireless, did you not call it?—sends messages to Houama here."

"So Houama is your wireless operator?"

"Houama is what you call the wireless operator," agreed Yacoob. "We will visit him when you have bathed."

"Golly! I quite forgot my morning bath. I've been so mightily interested I forgot I came out for a bathe."

Yacoob led to a pool, a disused salt pit.

Glad to find some refuge from the scorching sun, Tony was soon afloat on the water. The bathing pool was of great depth, but to sink in it was impossible, owing to the large amount of salt in solution.

The English boy splashed and tried in vain to dive in the swimming pool. The fierce rays of the sun on his head soon compelled him to return to his clothes and his sun helmet.

He was sparkling with salt crystals almost as soon as he was out of the water; there was no need of towel, the sun did the necessary drying, and Tony dusted the salt crystals from his skin with his hands.

"Now, Yacoob, let's get back to lunch," said Tony, looking round for Aa.

But Aa had already run off, and was superintending the preparation of a meal for Tony in Yacoob's quarters.

Entering the city again by the crawling holes, again Tony was struck by the air of mystery in the deserted lanes, the barred doors and the lack of living persons in the Secret City.

In Yacoob's courtyard, under an awning of dried palm leaves, Aa had set the meal, tinned goods from the Crimson Caterpillar, all that now remained of the stores that had been supplied for the journey to Timbuctoo.

When the meal was finished Aa knelt at Tony's feet and spoke rapidly in the unknown tongue of the Grey Tuareg.

Yacoob translated: "Aa says his father is grateful for all you have done, white stranger, as he considers that you did not know the evil you brought with you. Padaa invites you to see the temple and the city beneath the sand when the time is ripe."

Tony patted Aa's head. "I am still dithered about the whole business," said the English boy, "but of one thing I'm certain, you folks of the Secret City are a decent crowd."

Yacoob acted as interpreter and Aa said he must absent himself for a while, as he must "go below."

"Au revoir!" was Tony's response.

So, with his young forehead creased like an old man's, Aa ran off, whilst Tony joined Yacoob in a siesta which lasted till evening.

It was customary for the citizens of Ichaf to sleep from midday till four in the afternoon. Usually about six the work of the day resumed, continuing till ten. During the times of full moon, day was turned into night and night was turned into day—as far as work and sleep went.

In the cool of the evening Tony asked Yacoob to take him to see the Crimson Caterpillar and the wireless expert of the Secret City.

Through lanes whose doors shut suddenly as he passed, where wayfarers whisked off through unseen portals, Tony came to the crawling hole out of the city to the moat, and again by the second crawling hole of the outer wall to the sand hillocks where the Crimson Caterpillar had been left the night before.

There she stood under an awning of palm leaves, and on a tablet of sand erected by the car were words in a language not known to Tony.

"The edict of the High Priest," announced Yacoob, "declaring that he who touches the car, save by the permission of the white stranger, shall receive the punishment of Exile."

"Exile—what may that mean?" Tony asked.

"There is only one punishment inflicted by the High Priest, who carries out all the administration of justice in Ichaf. It is very seldom that the sentence of Exile is pronounced, and only then if the offender remain obdurate. He who is condemned to Exile is driven forth into the desert without steed or food."

"And what if he return?"

"He never returns, knowing his sentence to be just," Yacoob said solemnly. "He walks outward from the city till he can walk no more. Then he sits down and waits for death."

"Look here!" cried Tony. "I'm not going to have anyone driven to death in the desert merely because he has touched the Crimson Caterpillar."

"The law of the High Priest may not be disputed, white stranger."

"But, hang it all! somebody will have to touch the car. I want someone to help me polish up the old bus. Henri will be as wild as a wolf if he finds the Crimson Caterpillar dirty."

"Your permission, white stranger, relieves the one who touches from the dire consequences of his act." Yacoob pointed to the salt tablet.

"We'll have an overhaul of the bus to-morrow, Yacoob. Now we may as well look up your wireless operator and see if we can get a message through to Henri."

Yacoob nodded. "Houama will communicate with Amadhou in Timbuctoo without wires."

Wondering what sort of wireless station he should find, Tony followed his conductor back into the city of narrow alleys.

At length, as darkness fell like a pall on the mysterious city of the desert, Yacoob brought Tony to a doorway and rapped thereon five times.

Something sounded like a whistle.

In response Yacoob put his lips to a round hole and blew.

The door flew open, without human assistance as far as Tony could see. Even then Tony could discern nothing. Through the darkness Yacoob led the English boy.

There came a halt at a barrier of brick, breast high.

A voice spoke out of the darkness. "I cannot get through," came a wailing voice. "I cannot get through."

Tony grew aware of a tiny oil lamp and a figure looming up the other side of the brick barrier.

"I don't think much of your Broadcasting House, Yacoob," Tony said. "I can't say I'm struck with the furnishing of it."

Yacoob seemed puzzled. "Houama says his brother must be ill. He cannot speak with him."

"Tell him to try again," begged Tony, getting anxious: anything might have happened to Henri in that city of Timbuctoo with that villain Sidi ben Baar out to murder him. "He must get through."

There was a silence of minutes.

Then a startled exclamation out of the shadows where the figure loomed.

"What does he say?" Tony cried.

"Be quiet," commanded Yacoob, "or Houama will not get his thought through."

Suddenly there was a wailing cry from out the shadows, and a cataract of words!

"What does the wireless operator say?" cried Tony.

"He says that Amadhou has been stricken with dire illness so that darkness was over his mind. Amadhou knows not how long the stroke of darkness has lasted, but he says death and destruction are on their way to the Secret City—that Sidi ben Baar is at our very gates."

"But—but I thought Ichaf was a Secret City," stammered Tony.

"She was!" cried Yacoob in tragic tones. "But the spoor of the fire-car is unmistakable."

Tony bit his lips with vexation and despair. "What a fool I am! Of course the Crimson Caterpillar has left a trail that our enemy can see plainly written on the desert sand. What can be done? What can be done? I have betrayed you all to that ferocious mad dog, Sidi ben Baar."


CHAPTER XVIII
ON THE HEELS OF SIDI BEN BAAR

THE blind physician Amadhou had not ceased his droning cry, prophesying death and destruction to all his plans, when there came a drumming on the door of the magician's den, making Henri reach for his revolver.

Amadhou, stiffening to attention, waited for a fivefold tap, then pressed a finger on a disc on the table.

The door swung open—to reveal Esaf in a state of great agitation. "We must set out for the Secret City at once, Capitaine Leprince. The enemy are here and they are also there!" He pointed his forefinger eastward. "I have set the murderous emissaries of Sidi ben Baar on a false trail, and we must escape before they discover they are lying in wait for a man they do not want. It is the blood of Capitaine Leprince they seek to shed; his head they would take back to Sidi ben Baar."

"Tell us all you have unearthed, Esaf," Henri cried, whilst Amadhou sat rocking on his stool, both hands to his head, a picture of utter despair.

"I went forth in the early morning before ever you were awake, Capitaine Leprince," responded Esaf, "and the deeper to conceal my identity gave out to gossipers that I sought a man of the roumis. Soon it came to my ears that, throughout the night, four Tuaregs had been combing Timbuctoo seeking a French youth who had played traitor to Sidi ben Baar. One of these four was caught trying to sneak into the Reginal Palace, thinking to find you, Capitaine Leprince, under the protection of the Commandant. Two others are watching a house near the mosque of Djidji Riba, where I have caused them to think Capitaine Leprince is in hiding. 'Tis the biggest den of cut-throats in Timbuctoo that hide there, and if the two Tuaregs force an entry they will get cracked skulls for a certainty. But the fourth Tuareg is still roaming the city seeking us, Capitaine Leprince, and out on the desert are other Tuaregs who would prevent us from following their master and the car he intends to capture."

"Shall I go to the French Commandant?" cried Henri, turning to Amadhou.

"He has orders to detain thee in prison," answered the blind physician, "and has sentries placed with orders to capture the fire-car immediately it enters the city gates."

"But why?"

"I cannot learn," cried the distracted magician. "The air is full of messages and my brain is sick. Yet this much I know: ye must escape from this place and seek the Secret City, for there you may avert the tragedy that threatens to envelop us all."

"Come!" cried Esaf. "I have made all arrangements for our departure."

From a cupboard concealed by the mummy case Esaf drew forth two Arab robes. One of these he flung over Henri's shoulders, the other he adjusted to his own shoulders.

"Where are we going?" demanded the French youth; "and how can we escape the chain of Tuaregs who would prevent us following the Crimson Caterpillar and those who threaten to destroy her?"

"We go to the canal of the River Niger," replied Esaf. "I have seen a friend of the Secret City, and our barge awaits our coming."

Esaf spoke words unintelligible to Henri, bidding Amadhou farewell.

Henri looked with pity on the blind giant swaying on his stool. "Have no fear, Amadhou," the French youth cried, as he followed Esaf. "We will save the Secret City and the Crimson Caterpillar."

That was the last sight of Amadhou that Henri ever was to have—that blind magician rocking in despair, hands held to head. For three minutes after the fugitives had fled Amadhou crashed to the floor in a deathlike swoon.

Slinking forth into the sunlight, seeking the deepest shadow, Henri and Esaf were glad of the high walls surrounding the mosque Djameh Sankoreh. By obscure lanes the two fugitives hastened to the canal which connects Timbuctoo with its port Kabara. Nine miles south of the town lies the Niger.

A barge with large cabins amidships, belonging to an agent of Amadhou, was in waiting, and no sooner were Henri and Esaf aboard than the Laptots, black boatmen using pole and paddle, thrust off, making the utmost speed to reach the river.

Kabara was reached without mishap, and soon the barge was afloat on the broad bosom of Mother Niger.

Hidden in the cabin, however, the two fugitives saw little of that great African river flowing through the continent for two thousand five hundred miles, nothing of the thorny bush country bordering its banks beyond Kabara, of the high grasses where birds abounded, of the crocodiles basking in the mud, of the little villages where blacks watched the barge's passing, of distant sand dunes watching there like the outposts of an army planning to inundate the great bush land of Central Africa as they have done the Saharan land.

Once, when the barge collided with a hippopotamus, Henri ran forth to see the river, a wide expanse, fiercely lustrous with the sun's rays.

Esaf ran after him and hauled Henri back into the seclusion of the cabin. "Even the river banks may conceal the watchers of Sidi ben Baar, Capitaine Leprince. We are breaking through the enemies' outposts and must not be seen; we are outwitting those who keep close watch on the desert. When the sun sets, we come to the place arranged, and land in the darkness to find our steeds awaiting us. Thence we gallop to the desert, having come in between those who would stay us and the force of Sidi ben Baar."

It was a misty evening on the Niger's bank when the Grey Tuareg and his disguised companion landed.

From afar came the throb of a solitary tom-tom.

High reeds masked the movements of the barge, and no stranger saw Henri and Esaf land.

Led by the beating of the tom-tom the Tuareg sped to a spot amongst the sand dimes where a sallow-faced youth waited with two horses and a sturdy pack mule.

A slight repast of dried dates, washed down with a little water, and Esaf, leading the pack mule by a rope attached to the bridle of his own horse, declared they must be going onward. Waving farewell, with a fourfold tap on his breast to the sallow-faced boy of Amadhou, Esaf set his horse's head to the sand dunes on the sky line.

The moon was shining brightly and the Niger, a silver-spangled streak between misty banks, was soon lost to view as the Arab horses galloped hard on into a land of desolate sand hills.

At length Esaf gave a cry of satisfaction. "See there! Many riders have passed. It is the force of the Sidi ben Baar hot on the trail of the car that publishes its going on the sand. Here we must rest an hour; our horses demand it."

Already the pack mule had planted its fore hoofs deep in the sand, refusing to budge without compulsion. The two Arab steeds, their flanks lathered in sweat, their breath coming from them in what seemed smoke, settled on their haunches as soon as their riders dismounted and settled down to sleep.

Esaf passed Henri a handful of dates, but the French youth was too fatigued to eat, though he accepted with great satisfaction the cupful of water the Tuareg handed him.

Though Esaf seemed to drop to sleep instantly, Henri lay awake, full of anxiety for his cousin Tony and his beloved Crimson Caterpillar. He was feverish and kept picturing the breakdown of the car, his cousin's futile endeavours to repair the damage, the triumphant arrival of the relentless Sidi ben Baar at an unprepared city, the capture of the much-wanted bar of salt by the enemy, and the total destruction of the Crimson Caterpillar.

Although Henri, however, was in a fever to get on, he made no attempt to awaken the sleepers, human and equine. They knew the desert and its ways better than he!

The French youth had dropped into a light doze when the bustle of departure awoke him to full consciousness.

"We ride on through the night," Esaf said grimly. "You must take some food, Capitaine Leprince, or you will fail before the morning and so delay us."

Henri took the proffered dates, forgetting those already in the pocket of his robe, and soon was following Esaf through the night.

The veiled riders, for the Arab disguise had been left behind on the barge, rode onward, the drumming hoofs of their steeds the only sound that broke the stillness of the desert.

With necks outstretched the four-legged heroes plugged forward through the heavy sand, needing no spur, knowing that haste in that world of sand was necessary to life.

French and Grey Tuareg strained eyes ahead, looking for Sidi ben Baar's force or for stragglers from his company.

That relentless warrior, however, had twelve hours' start of the two who followed after. The Sidi spared not his horses, his camels nor his men; he was in mad haste to possess the salt bar on which the whole success of his enterprise hung.

The skies of the eastern horizon grew pallid with dawn, then purple, then pink, then saffron, till the great molten disc of the sun peered over the myriad billows of the sand dunes.

"We sleep now," Esaf said as he drew up his horse and lurched from the saddle to the ground.

Henri's steed followed suit, but Henri did not dismount. The French youth was asleep, or as near asleep as a man may be who still clings to the saddle.

Henri was lifted from his horse, and instantly fell fast asleep when Esaf lowered him to a hollow in the sand. He slept so long that, as the sun mounted the sky, Esaf reluctantly roused him.

"We must ride on," he said. "The Secret City needs us."

"Yes, the Crimson Caterpillar needs me," Henri agreed sleepily, and gratefully accepted the draught of water Esaf offered.

There was a fearful ordeal ahead for Henri, riding on and on through that blazing world of sand. Henri was no horseman, and after two hours' hard going sand-devils with pronged spears danced before his imaginative eyes, shimmering waves of heat hit him in the face so that he gasped aloud, and mirages of palm and pool rose on the horizon to mock him.

Henri Leprince, however, was every inch a gallant Frenchman, and strove to keep up with the Tuareg, who had been born to the saddle. His head was throbbing as if it would burst, and he was wondering which of the six Esafs before him ought to be followed. Every single bone in his body seemed to develop an ache, and every muscle seemed wrenched out of place.

He shouted as he felt his senses leaving him, and he was glad to see that all six Esafs were coming to his succour.

The next thing Henri remembered was the trickle of lukewarm water down his parched throat, then a strong arm around his shoulders, a reassuring voice in his ears.

"Courage, Capitaine," urged Esaf. "After you have taken a little more water you must rest. We all must rest."

Once again Henri sank into deep dungeons of sleep. He woke only when the cold of the desert night nipped nose and ears.

Esaf had covered the French youth with his own robe and was sitting, leaning against his horse for warmth, staring out into the night.

"I have seen no sign of the Sidi's camp fires," said Esaf sadly when he saw Henri was awake. "He rides in frantic haste, and we must needs follow."

But Henri found he was too stiff to stand, and his brain was reeling so that Esaf seemed to waltz before him. "I fear I have fever, Esaf," he faltered.

"Yet must you ride, Capitaine Leprince," said the Tuareg quietly. "I cannot leave you here to die."

"Ride on," said Henri wearily.

To Esaf death in the desert was no new thing, death by thirst and starvation was as everyday an occurrence on the desert as a taxi-cab crash in a Parisian street. "You must mount, Capitaine Leprince, and follow me as quickly as you can. I will ride only a short distance ahead."

Henri was propped in the saddle and, calling all the resolution of his nature to his aid, he tried to follow his companion onward through the night.

They reached the huge basin bounded by sand dunes where the surface was slate-like and treacherous, and there they met the crowning catastrophe.

Esaf's horse stumbled and flung its rider clean over its head.

Henri slid from his horse, pain racked and almost delirious. This was the end of all things!

Esaf lay motionless, and, turning him over with difficulty, Henri found a red gash on the Tuareg's forehead. The horse had bolted and the pack mule had followed.

Henri managed to hobble his horse, fearing it would bolt after its companions. Having some knowledge of first-aid, he felt his comrade's pulse and found it still beating. With a strip torn from the Tuareg robe he bound up the bleeding head.


CHAPTER XIX
THE CITY BENEATH THE SAND

IN the cell of Houama, where Tony had learnt the fateful news that Sidi ben Baar was hot on the Crimson Caterpillar's track, there was a hasty consultation between its strange owner and Yacoob.

Yacoob turned to the English boy. "The Sidi and his men cannot be here till three nights have passed, white stranger, wherefore grieve not before it is time to grieve. Much may happen before the villain reach our holy city."

Tony brightened. "There's plenty of time to put the city in a state of siege, to mount guns and sharpen spears."

Yacoob looked earnestly at Tony. "Have you forgotten that the followers of Christos may not fight?" he asked reproachfully. "We cannot resist the invaders with weapons, for we cannot kill."

Tony muttered under his breath: he didn't want to be rude to his hosts, but—

Yacoob continued: "More than one raid has swept our Secret City, but the sweepings did not pay to take away."

"But your citizens cannot all escape, surely, Yacoob."

"The raiders saw few of our citizens. The few old men and women left above ground were able to pass by winding lanes and to laugh at their pursuers as they took refuge behind barred doors which, when forced, yielded no captures, for the citizen had passed through other barred doors, or, escaping to the roof, sought the security of other apartments. If too feeble to flee, then they were of no value to the raiders as slaves. Besides, seeing the aged citizens did not resist, there was no need for the raiders to kill, unless in wanton rage. And the raiders of the desert are not wild beasts. As for the women, children and young men, whom the raiders might desire to take into captivity, they were not even sighted."

"Why?"

"Because they were below," said Yacoob. "Come and see for thyself, for as we talked a few minutes ago Houama told me Aa had secured permission for you to come to the underground temple—to our city beneath the sand."

Tony was eager to explore, and quickly followed Yacoob as he passed from Houama's cell out into the winding alleys.

Houama's cell, Yacoob pointed out, was built into the inner wall of the city of Ichaf, but they had to penetrate to the city's centre before the "way below" might be found.

More than one barred gate was opened by the password used by Yacoob, but the uncanny thing to Tony was that no sentry was once seen, gate or door was unbarred as if by magic.

"It is custom that a man should not show himself," explained Yacoob. "The porter hides behind the door or in a compartment beside the gate difficult to detect."

They came to a mere hole in a wall, and, following Yacoob, Tony found himself in a considerable courtyard at whose centre was the mouth of an ancient well.

"Look and wonder!" cried Yacoob. "I show you that which no white stranger yet has seen—the main entrance for passengers to the Sacred City beneath the Sand. Our goods are lowered at another well. And there are six such wells within the city above."

Tony stared with amazement at the great beams about the well's mouth, tough, hard wood worn into grooves by the friction of ropes, and so deep were the grooves that Tony calculated that only centuries of use could have made them. Even the rock face itself, for the shaft was sunk through solid rock, was marked with long grooves disappearing into the darkness below, grooves made by the friction of so soft a thing as a rope.

"Aa has gone down there?" Tony asked, in an awed whisper, as he gazed down the well.

"He has descended to his father, Padaa, the High Priest who permits your descent, white stranger," Yacoob replied.

"Shall I go down first?" Tony asked without much enthusiasm.

Yacoob bent over the well mouth and uttered a fivefold cry in his own language.

In the space of two minutes a youth's head hove in sight. He was climbing hand over hand up a rope, and did it with an agility that Tony had never seen equalled. The boy was not unlike Aa; there was the same whitish cast of countenance, the same yellow eyes which shone weirdly out of the shadows at the well mouth.

The newcomer from below climbed out over the seared beams and stood before Yacoob. He appeared to ask certain questions, looking askance at Tony.

Then, as strangely as he had arrived, he descended into the depths again.

"He is a faithful lad," said Yacoob. "He will not abet the intrusion of a white stranger into the hidden city beneath the sand unless he has the personal permission of Padaa's own self."

While the boy was gone Tony took the opportunity to ask several questions.

"Do you mean to tell me, Yacoob, that men and women are living away down that well in a subterranean city?"

"Yes, and few of them come up oftener than once a month or when they take their turn at the salt pits, which is about once in six months. As for our High Priests, they never leave the underground city."

"When Aa steps into his father's place, do you mean to tell me he will be a prisoner for life in that city below?"

"It is our custom, and a High Priest is always proud to serve his race," replied Yacoob.

"How far is the well sunk?"

Yacoob seated himself on the grooved timbers at the head of the well, signifying that Tony should do the same. "The wells sink far into the rock till they reach the level of the city of the Ancients. For know, O white stranger, that when the world was young the Sahara was a pleasant land, with an inland sea and fertile countries about it. And there were beautiful cities and palaces which the sand overwhelmed."

"And how is your city lighted, Yacoob?"

"We use palm oil lamps sparingly, but we can see in darkness when you white strangers are blinded by it. From of old the eyes of the Ichafians have accommodated themselves to darkness, and we can see in the dark like the lion or the puma can see."

"How far does the city stretch, and what—"

"I will tell you more another time," interrupted Yacoob. "The signal has come for us to descend."

A big bucket came into sight and swayed at the mouth of the well.

"Step in," said Yacoob, and the two of them stood in the bucket whilst they were lowered into darkness by means of a windlass manipulated from below.

For what Tony reckoned to be about eighty feet the bucket was lowered, and he came to a standstill with Aa's voice to greet him.

Aa held in his hand an earthenware lamp, such as Tony remembered seeing in a collection of Roman remains, a sort of cup with a narrow spout.

"Aa will take us to his father," Yacoob said.

Tony could see little in the meagre light of the one oil lamp, and he felt in his pocket for the flashlamp he always carried. But Yacoob forestalled him. "Don't use that," he cried, "you may need it badly when Sidi ben Baar comes."

So Tony groped his way along what was, as far as he could see, a thoroughfare of some dimensions, and he felt rather than saw the passing folks.

"The High Priest will be pleased to see you," Yacoob said. "My brother knows how kind you have been to his son Aa, and so he gave consent to your descent to the city which white stranger never yet has seen."

The roadway was bordered by low stone buildings that looked like part of the sandstone into which they were built. Here and there were larger edifices which might have been public buildings. And in all the curious houses were latticed spaces that did duty as windows.

They came to cross-roads where were several big lamps, enabling Tony to note the grey features and yellow eyes of the inhabitants, all clothed in the characteristic Tuareg dress. He saw, too, big sleighs drawn by porters along the sandy road, bearing cones of salt and other commodities. He wondered at it all, and his brain was full of questions.

But Yacoob broke in on his thoughts. "We reach the temple where the High Priest lives. Aa enters to announce our arrival."

Before Tony stood a building, severe in its architectural simplicity, apparently built of white marble. A door of ebony gave entrance, and on either side of this door was a cross inlaid, blood red in colour. Apart from this decoration Tony could discern no ornamentation, only two latticed spaces rather bigger than those to be seen in the ordinary dwellings of the Ichafians.

Aa had gone in as the door opened in response to a five-fold rap. He now came out, bearing a lamp, and beckoned Tony to enter.

Down four steps the English boy went, to pass into a cool interior, with the sound of running water coming to his ears, the fragrance of some sweet-smelling incense delighting his nostrils.

He gazed about him, and in the meagre light sensed a plain stone hall of huge dimensions, the ceiling of which he could not see, so far above him did it stretch. Three walls were to be seen, the white stone reflecting back the light, but on the fourth side, facing the narrow portal by which they had entered, there was a background of sheer blackness, a void out of which echoed the sound of running water.

But against this blackness was that which at once struck the worshipper in this strange temple. On a raised platform was an altar gleaming white, and above the altar, as if hanging in air, a white cross. Later Tony was to learn that the cross was of white marble, mounted on an ebony pedestal which could not be detected against the void above the river which constituted the fourth side of the temple.

A row of six lamps burned at the altar's base, flinging up altar and cross in bold relief against the pervading blackness. No other decoration could Tony detect in that austere temple beneath the sand. To the right was a small doorway leading to the private apartments of the High Priest.

From this doorway came a Utter borne by four youths clad in white robes. On the litter was one clothed all in white, the hair of his head and beard white, though the gleaming eyes did not appear to be those of an old man.

"Allah be with you!" was the greeting of the High Priest as his litter was set down beside the visitors. "Your goodness to my son is known full well to me. Though I know not with what evil intent your fire-car brought that to the desert." Padaa pointed to the altar, and on it Tony could detect what he had no doubt was the identical bar of salt on which Jambonne had scratched the crescent sign.

"Henri, my cousin, and I are perplexed about the matter," replied Tony in French, in which language the High Priest had spoken. "But I assure your holiness that we had no evil intent in our minds."

"That much I have already read in your face," replied Padaa. "But before we speak further will you not take a draught of our beautiful river?" And the High Priest pointed to the darkness whence came the sound of running water.

On Tony replying that he would be honoured by such hospitality, a golden goblet was brought to him and he drank from it water with a distinctly saline taste.

He handed the golden goblet to the youthful server who had presented it, but the boy held back and would not take it.

"The goblet is yours," said the High Priest. "Aa would wish you to understand our gratitude for all your kindness to him, O son of the roumis."

Tony turned to Yacoob. "It looks like gold," he whispered. "I don't like taking it."

"Don't hesitate," replied Yacoob in Tony's ear. "'Tis solid gold, the work of the Ancient Ones. But we have many such, chambers below"—Yacoob stamped the floor—"crammed with gold and treasure. But of what value is it in the desert? Here life-giving salt is vastly more precious."

But Tony was growing anxious; these folk seemed to be making no preparation for resisting the oncoming invader of the Secret City. "Holy sir, do you know that an evil warrior comes to take back the bar of salt upon the altar?"

Padaa smiled. "Never will the Sidi ben Baar discover Ichaf, excepting such of our city as is above ground. The city beneath the sand will remain the secret that it has remained down through the ages. But there is one small matter about which I am concerned."

"And what may that be, holy sir?" asked Tony.

"My son Aa tells me the fire-car on which you came here is too large to lower to the Secret City," Padaa replied. "May it be cut into bits and lowered in sections, or shall we conceal it by building over it a mound of sand?"

Tony shuddered at the thought. Henri might have done something to dividing up the Crimson Caterpillar into its various parts, but he—Tony—could not tackle the job. As for the car being buried in sand, that would be the ruin of the engines, it seemed to him. Yet what otherwise could be done to conceal the Crimson Caterpillar from Sidi ben Baar, who would be mad with rage when he found no salt bar in the rumble?


CHAPTER XX
LIFE IN UNDERGROUND ICHAF

TONY MASE slept in the High Priest's apartments on his first night in the city beneath the sand. Aa's mother had died when he was an infant, and those who waited on Padaa were the four youths who had borne his litter.

Yacoob had returned above ground; he had much to do in superintending preparations against the coming of the raiders.

Aa showed great delight in acting showman of the subterranean city; his solemn little face grew quite animated. Tony was so interested that he bubbled with questions, and Aa was full of explanations; but as each spoke a tongue unintelligible to the other Tony did not learn much.

The underground river was of the utmost interest to the English boy. It flowed between banks of rock topped with a low parapet. Tony judged it to be eighty feet across, deep and swift flowing. Its course, Padaa told him later, was in a mountainous region similar to the Ahoggar, and it discharged its underground waters into the Niger.

The river certainly brought refreshment and life to the city beneath the sand, and the English boy learned that it acted as a ventilating shaft; the six wells and the inflow and outflow of the river were all part of a system whereby the underground atmosphere was renewed.

By the banks of this river Aa brought Tony to an enclosed pool.

Aa handed over to Tony the lamp he carried, then flung off his loin cloth.

Tony turned at a noise behind him—some other boys of Ichaf were approaching.

He heard a splash. Aa had disappeared. But, on lifting high his feeble lamp, Tony detected the oily surface of the pool disturbed by the ripples caused by Aa's dive.

There came a shout of delight, a sentence which was an invitation. Tony peered in the direction of the shout and saw Aa's frown appearing above the water.

There were a couple of splashes a few feet off. The three Ichafian boys had joined Aa in the swimming baths of the underground city.

Soon Tony joined the happy boys in the baths, but it was rather weird swimming in the darkness—a darkness just made visible by the one lamp Aa had brought and which Tony had left by the river's side.

After the swim Aa took Tony further along the river banks, and there, not far from the spot where the river took its plunge under the underground city, he saw some sort of system of drainage being carried out, whereby the sanitation of the city was controlled.

More than one bridge spanned the river, and Tony caught glimpses of low buildings and walled spaces, but it was a dismal enough prospect with no sky overhead, no vegetation, no colour, and a semi-darkness that was eternal in that city beneath the sand.

No wonder that the Grey Tuaregs of Ichaf were so pallid. No wonder that, like Aa's, most of their foreheads were creased.

Even at this crisis the inhabitants whom Tony met went about their business calmly and confidently, though aware that a ruthless raider was riding hard with his followers down upon their undefended city.

The inhabitants were, indeed, of an unemotional nature, never laughing and seldom crying; they lived content with their lot, their religion breeding in them a faith serene and hopeful. Yacoob explained to him later that the people who lived below saw a thousandfold more in the darkness than Tony could even guess at. And recalling the yellow eyes of Aa and his relatives, and the gleaming eyes looming up like cat's eyes in those subterranean streets, Tony could realise that he was a blind man amongst a multitude who saw.

Turning from the river, the two boys came to the bazaar. Women sat at stalls or by baskets selling spices, capsicum, raw cotton, but mostly dried figs. Men stood at booths measuring off cloth. But as each stall and booth was lit only with one mere pip of light, the busy market was rather like a fitful dream to Tony, as soon as his eyes fixed on one tiny glow of interest it faded out as he passed on to further little circles of interest. All the marketing, apparently, was carried on by a system of barter, but in small transactions salt seemed to be used as the medium of exchange.

"Jolly nice when you want to buy some sweets," remarked Tony to Aa. "You just run to the mines, pick up some salt, and come back for a pennyworth of chocolate—or whatever goody you sell in this strange bazaar."

Not understanding one word that was said, Aa, in reply, explained how the goods reached the bazaar through the Tuaregs of the Beyond, who came each month to trade for salt.

At which explanation Tony, who understood not one word, said it was all very intriguing and would Aa take him to the next place of interest.

Beyond the market was a big stone barn into which Tony was allowed to look, as he was in the company of the future High Priest of Ichaf.

In it were being stacked cones of salt similar to those Tony had seen being made at the salt mines. The cones were coming down an inclined plane, doubtless through a "well" in the city above. Bar after bar was stored away. Though the salt seldom came to the subterranean city for storage, there was every provision made for removing the wealth of the oasis out of the reach of a raider.

By another "well" there descended household goods, lowered by their owners for safety's sake, for no one could tell how thoroughly Sidi ben Baar would ravage the city. Though it was believed by the High Priest that the raider could not remain at the Secret City very long, seeing he would not have victuals for feeding his force. Even the old people who remained above were only allowed three days' ration of dried dates—and these they hid.

It was as strange a siege for which Yacoob and his fellow-citizens prepared as a man of the modern world could well imagine.

The sight-seeing finished for the time being, Aa took Tony to his apartment in the temple, a simple room with a stone bench as bed, a stone table and stone chairs, all replete with goat-skins.

Below in that subterranean home Tony slept and ate. He was treated as an honoured guest, but was not permitted to return to the upper city, all the shafts being closed except for such of the citizens and their goods as were descending.

The High Priest, who spoke French fluently, was Tony's only source of information now that Yacoob was busy above ground, hastening on the passive resistance to the raiders who were expected to arrive that night.

Tony awoke from sleep, but whether it was day or night he did not know. His watch had stopped, clogged with sand, and he had no indication of the passage of time. The Ichafians used nothing answering the purpose of clock or watch.

The English boy begged the High Priest to allow him to ascend and ascertain the condition of the Crimson Caterpillar, but Padaa would not give consent.

"All is being done that can be done; my brother Yacoob is a man of ability," the High Priest said, as four youths, clothed in white, came to the living room in which he and Tony sat conversing. "Permit me to invite you, O son of the roumis, to join us in adoration of Christos Who taught that men should always pray and not faint, pray and not be anxious for the morrow, pray and not fight."

Tony followed the kindly Padaa as he was borne forth on the litter by the four youths to the altar under the white cross that appeared suspended in air.

It was very strange, that religious service in the subterranean temple, and to Tony it seemed more like a dream than solid fact.

Silently the Grey Tuaregs trooped into the temple and knelt.

There was no chanting or singing. The High Priest repeated certain prayers in the Tamashek dialect used in Ichaf, and then all joined in.

Aa sat on the altar steps, Tony remained with the four youths and the litter.

The only part that Aa took in the simple service was to stand erect at its conclusion, whilst his father placed his hand on his curly locks.

The people, still kneeling, as one man breathed the one word, "Aa." It was the Ichafians' recognition of Aa as their future High Priest.

Tony watched, almost with irritation, the calm demeanour of the worshippers as they filed out into the street, showing not the slightest sign of fear.

And yet, out of the desert, was swooping down a ruthless leader and his wild followers who would stop at nothing to secure the salt bar lying there on the altar—undefended!


CHAPTER XXI
A HOPELESS CHASE

THE chill of the zero hour which precedes the dawn stirred some semblance of life in two human figures stretched on the desert sand.

It was Henri Leprince who was the first to sit up and look around. His first thought was for Esaf, who had been flung from his horse and sustained such a sad wound in his forehead.

Esaf was muttering words unintelligible to the young Frenchman, but the bandage about his head was in order and there seemed to have been no further bleeding from the wound.

Henri's second thought was for their steeds. These, he was pleased to see, lay close to their masters, though they had not been hobbled the night before.

Henri tried to arrange his muddled thoughts; fever was still in his brain. It seemed weeks since they had sneaked off from Amadhou's house in Timbuctoo to hide aboard the barge that had carried them some way down the Niger. And from the time of landing until the present moment all was a fearful nightmare in Henri's recollection.

The French youth waited till some sign of consciousness showed in the Grey Tuareg's eyes. "Esaf, we must break fast and ride on," he said presently. And repeated the remark three times before his companion comprehended.

"Yes, Capitaine Leprince," was the drowsy response, "we must ride on and seek the Salt Bar."

Dried dates were the only nourishment the riders would allow themselves, the little water remaining in the goat-skin was reserved for their steeds, on which so much depended.

"There is no well," said Esaf, "till the Secret City is reached—if, by the mercy of God, we do reach it."

As the pink and gold rays out of the East stole over the sandy wastes that stretched on every hand to distant horizons, the two sorely-tried travellers took heart. Esaf's wound was healing rapidly and Henri's fever had abated.

As the day drew on a stiff breeze blew over the surface of the desert, and, as far as Henri could see, the tracks of the Crimson Caterpillar and of the pursuing Sidi and his followers were obliterated.

"Do you not think this wind will cover up the marks of the caterpillars, Esaf, so that the Sidi will lose all trace of the car?" Henri asked hopefully.

Esaf pointed to the sand. "The marks are all there plain to see, Capitaine Leprince. And the Sidi will reach the Secret City during the coming night."

Henri sighed despairingly, if Esaf's desert-trained eyes could detect the tracks of the Crimson Caterpillar and of the camelmen and horse of the Sidi, his city eyes certainly could not. If Esaf collapsed, Henri knew he would he lost and helpless.

"How soon shall we reach the Secret City, Esaf?" Henri enquired anxiously some hours later, for the Grey Tuareg was swaying in his saddle like a senseless man.

There was no answer, and galloping a trifle ahead Henri shouted back: "How soon shall we reach the Secret City?"

"When the enemy have already violated the sanctity of Ichaf," was the gloomy reply; "and when the Sidi has captured his salt bar."

"But, my brave one, you are not yourself," Henri urged as the horses slackened to a canter. "Hitherto you have been full of hope, and now—"

Esaf crossed himself on his breast. "It is my head wound that tampers with my faith and fortitude," he wailed. "Yet I will be brave henceforward."

The day was a repetition of the preceding one, a dreary progress across endless sand dunes, a plunge into the trough of the sand sea, then a laborious stumble upward to the summit of another sand billow.

Esaf, closely watching the signs that he saw in the wind-driven sand, told Henri that the Sidi's warriors had not kept always to the tracks that the Crimson Caterpillar had made. Aided by his scouts, the Sidi's party had avoided the detours that it was necessary for the car to make. The Sidi had taken short cuts across the sand dunes, and, if ought had gone wrong with the fire-car, it might be that the Crimson Caterpillar was already in the Sidi's hands.

"It's a hopeless chase and a mad one," cried Henri. His throat was burning and his tongue was swollen; he was suffering the first torture of a man denied water. "And indeed what can two men do? The gates of the city will be guarded by the Sidi's sentries, and—"

"Doubtless the crawl-holes of the city will be guarded by the Sidi's sentries, if he has got so far, for no resistance will be offered him. But there is a way into the city known to a few of us, Capitaine, and by that way we will go."

"If we don't die of thirst first."

"We will have a last cupful of water," Esaf announced as he slumped from his steed. "And here we will leave our pack mule who is rapidly failing and will not survive another gallop. There is little left for it to carry, and its allowance of water may save the lives of the other two quadrupeds."

"Will you shoot it?" Henri asked as he held out his revolver.

Esaf frowned deeper than usual. "Have you not learned, Capitaine Leprince, that no Grey Tuareg disobeys the command of Christos? We may not take life."

The animal lover was indignant. "Then you will leave the poor beast to die of starvation and thirst in the desert! I shall shoot it."

Esaf shrugged his shoulders. "Each man must give an account of himself to Allah," he quoted.

In the torrid heat of the day Henri's fever returned, and only the spirit of the young Frenchman kept his body from giving up the almost hopeless effort of reaching the Secret City.

The heat that day seemed a thousandfold worse to Henri than any that had preceded it. The sun blazed down from the brazen vault of the heavens as if it would bum up all life that braved the desert journey. The sand sent heat waves upward as if from the heart of a blast furnace.

The travellers' eyes burned in their sockets, and for a couple of hours Henri suffered from sun-blindness, following doggedly after Esaf by sound and not sight.

Their progress became a painful crawl. Henri longed for nothing on earth except Esaf's permission to lie down: he would die willingly rather than continue in this torment. Only—only there was his cousin's face hovering in the heat haze ahead, and—and the bonnet of the Crimson Caterpillar!

Blessed night came down with the horses proceeding at a funereal pace. Esaf had freed the pack mule from the empty goat-skin water-bag; somewhere, a mile or two behind, the dying animal tottered after its companions. Henri was quite unconscious of its plight.

"We go on till we drop from our saddles," said Esaf grimly. His lips were cracked and his throat crinkled for want of moisture; he had denied himself the midday drink, unknown to Henri. The Grey Tuareg could survive without water when the French youth, unused to desert privation, would die.

A certain amount of easement came to Henri with the going down of the sun, but it was cruel work plodding on when every nerve in his body cried out for sleep.

Out of the darkness ahead, when they had travelled on for what seemed to Henri an eternity, came Esaf's voice.

"We are close to the Secret City now," he said in a low tone. "Stay here whilst I creep forward to reconnoitre."

Henri rolled from his horse and almost instantly dropped into a state of unconsciousness.

Esaf hobbled the two horses and crawled forth into the night.

The next thing of which Henri was conscious was a voice in his ear.

"Come," it said. "The Sidi and all his force are within the Secret City."

"And what of Tony?" Henri asked, sitting up in the sand.

"They must be within the city beneath the sand—my brother and your cousin."

"And the Crimson Caterpillar?"

"That also is not to be seen. But it may be with the camels and the horses of Sidi ben Baar in the zareba where the sentries watch without the walls of Ichaf," Esaf explained. "That side of the city we must avoid lest we be discovered and slain forthwith, as the Sidi has commanded."

"But what is happening within the city?"

"That I cannot tell; Ichaf might he a city of the dead for all that comes to my ears, Capitaine Leprince. All that remains for us to do is to enter the city by the way of Houama's dwelling and to learn what is afoot."

Henri was much refreshed by his sleep and sprang to his feet, ready to follow Esaf into the Secret City of Ichaf.

"I shall crawl as silently as a serpent," Esaf said, "and you must creep no less silently. A careless action may create noise that will betray us to the Sidi and ruin us all."

"Will you not take the revolver, Esaf, as you go first?" queried Henri, taking the weapon from beneath his robe.

"Have you not understood yet that we of the Secret City murder not?" indignantly exclaimed Esaf.

"I will be close beside you, Esaf," said Henri, fingering his revolver suggestively.

Esaf sat down on the sand and folded his arms. "Unless you leave the murderer's tool behind you I cannot show you the way into the city. It is against the religion of Christos to murder—even an enemy!"

Henri protested, but Esaf would not budge. "It is against the religion of the Secret City," the Grey Tuareg kept saying, pointing to Henri's firearm.

Until at length, the French youth buried the revolver in the sand. After which, standing erect, he ordered Esaf to lead on.

Ten minutes later, Henri, crawling after Esaf, came in sight of Ichaf's outer wall.

Esaf pointed along the wall, and against the starshine Henri could detect the silhouette of a sentry. The Sidi's soldier was guarding the crawling-hole of the outer wall.


Illustration

The wall of petrified salt rose some twenty feet in air, and Henri could see no possible way of scaling the smooth surface.

Esaf, however, working like a mole in the sand at a spot indicated by a small cross scratched on the wall, revealed a hole through which they both could crawl.

The outer wall passed, Esaf led the way across the dry moat to the inner wall.

Again Henri failed to see how it might be scaled, and the buildings inside the wall gave little hope of a second tunnel like the one they had just used.

Esaf whispered to Henri to climb upon his shoulders and then to feel with his fingers for a hollow. Within that inconspicuous hole, Esaf said, Henri would find the end of a rope which he must lower for his companion's use.

Henri climbed as directed and found the rope end. He pulled at it and a coil of rope unwound from within.

Dropping to the ground Henri watched Esaf climb upward by the rope which remained attached within the hollow. Clinging like a very monkey, Esaf stretched upward till his fingers found purchase at the summit of the city wall. Tightly Esaf clung and signalled Henri to ascend by the trailing rope.

Henri reached Esaf's feet.

"Conceal the rope in the hole, then climb into the city over my body," Esaf whispered.

It seemed impossible that Esaf could support him, but the strength of the desert man was equal to the strain, and Henri found himself asprawl the city wall.

The French youth obeyed his companion's orders to lie close to the wall and to roll secretly thence to the adjacent roof.

There he awaited Esaf's coming with a thudding heart: would the Grey Tuareg have sufficient strength left to raise himself to the level of the city wall? Henri could scarcely restrain himself from crawling to see how his comrade fared, but remembered the strict injunction to lie low lest he be detected by one of the Sidi ben Baar's men.

"We are on the roof of the physician Houama, who can speak with his brother Amadhou in Timbuctoo," came a voice in Henri's ear. The Grey Tuareg had climbed so noiselessly that Henri had not heard him approach.

Esaf felt round and Henri could just detect a trap-door at the spot that the fingers of his companion stayed.

Five times Esaf tapped on the door.

Without visible help the wooden door opened quietly inwards, and Esaf dropped into the dark interior.

Henri, leaning over, felt his hand clutched. He was drawn swiftly after the Grey Tuareg.

The trap-door swung back into place, and not one glimmer of fight was there to be seen in that house of Houama. But Henri followed Esaf's leading.

Certain stairs were descended and they came to a halt in a cell-like compartment.

Henri could detect, though not by sight, that he stood by a wall, breast high. Though he did not know it, he was standing in the very spot that his cousin Tony had stood not long before!

Out of the darkness a tragic voice spoke.

"You have come too late, Esaf. The Sidi ben Baar is here and has found the secret ways to the city beneath the sand. Ichaf is doomed."


CHAPTER XXII
THE TRIUMPH OF SIDI BEN BAAR

SIDI BEN BAAR, riding furiously, drew up at the place in the sand dunes where his scouts were gathered, completely nonplussed. All traces of the Crimson Caterpillar were lost.

In response to their leader's angry question one of the scouts cried: "Verily we have come into an ambush, and dare not proceed."

"Verily desert fighters have been here," cried another, "and they are men of great guile who have swept palm leaves over the tracks that the fire-car made."

"Then follow the tracks the desert men have made," shouted an angry leader.

"They tread lightly and the wind has blown over their footmarks till no trace remains," pleaded the first scout.

"The darkness defeats us," cried the second.

"Follow me," cried Sidi ben Baar, who was not lacking in courage. "If men have been here on foot, their home must be at hand." And he galloped to the summit of the sand hills, peering north, south and east.

The Sidi gave an exclamation, and pointed to a distant line of wall revealed by the star-shine.

The outer wall of the Hidden City was seen by all that savage band of marauders.

The scouts, anxious to redeem their reputations, were not long in discovering the crawling-hole through the outer wall.

Crossing the dry moat by their leader's orders, they were not long before they located the crawling-hole into Ichaf itself, during which time Sidi ben Baar had formed his force into a zareba amidst the sand dunes.

The scouts came with their news to Sidi ben Baar.

"Silently we make preparations, and such as are weary may snatch an hour's sleep," announced their redoubtable leader. "At dawn we storm the city and put its inmates to the sword if they resist and will not deliver up the Salt Bar I must have."

The warriors, in the circle formed by their camels and horses, refreshed themselves as the Sidi ordered, and soon the zareba was silent except for the soft tread of sentries set to guard against surprise.

At the first show of light the Sidi led his men to the hole in the outer wall, and on foot the greater portion of his force gathered in silence within the dry moat.

"Verily it must be the city of the Grey Tuaregs," the Sidi said to his chief warrior, "that secret city which men have thought a myth. It is certain they are careless, for no sentry shows along the wall and no alarm has been raised. On, warriors, on; we will surprise them as they sleep."

Bearing rifle, sword and spear, the fighters crept through the narrow entry into Ichaf. Those to enter last pushed forward those who entered first, for there was little room to form in fighting array within, and the sinister silence preyed upon the spirits of men who feared no foe but believed in djinns and ghostly denizens of desert places.

"'Tis a warren of rabbits," growled the foremost man, pushed forward by his fellows, and a second later, failing to notice a step, crashed into the crystalline salt wall of the winding alley.

"And the rabbits be safe earthed," cried another Arab as he hammered at a barred and bolted door.

"I'll ferret 'em out," cried a third, producing his axe.

The door was battered down, and, swarming into a small compartment fit by a tiny oil lamp, the warriors found—three date stones on which one of their number slid backward.

Another door was battered down, and in the darkness nothing was to be detected but another door. And beyond that again a third door.

This the man with the axe promptly demolished. And the Arabs swarmed into a courtyard where was a well.

But there was no time to stop and refresh themselves now; it was prey they were after. They rushed forth, little guessing that the "well" might have solved several problems.

"On! On!!" shrieked Sidi ben Baar, who did not relish this dismal kind of warfare. "Doubtless the foe will be gathered in the city square, guarding the precious Salt Bar I so greatly desire."

The fierce fighters pressed onward, uttering fierce challenges to which there came no counter-challenge. And the alleys did not converge on the city square their leader sought.

It was distinctly disheartening to a full-blooded, howling dervish of a fellow to be met with a blank, stony silence.

"Unsheath your swords—when there is room to do so," cried an exasperated leader, "and cut down every rat of this accursed city of ghosts."

"Ghosts!" echoed more than one warrior with a shudder.

One nervous spearman, slipping on the uneven alleyway, prodded his leader with his spear point, and narrowly escaped a sword cut aimed at him by the enraged Sidi ben Baar.

At length a door was discovered with a voice behind it. It was a harsh masculine voice, but when the warriors beat down the door an old woman bade them begone for rude shamers of decent women. And when they hesitated because of the press behind them in the lane the old lady rose from her bed, seized her broom—she was sure the High Priest wouldn't reckon it as a weapon under the circumstances—and drove the warriors off with damaged pates.

Nor was the marauders' next discovery more satisfactory!

It was the Sidi ben Baar himself who noted the light that gleamed from above a certain door. He charged that door with his great brute strength; all other doors encountered in the Secret City had been bolted and barred. But this door was not even latched, and the Sidi went asprawl into the room, two of his followers atop of him.

Calling down curses on all, the Sidi extracted himself, determined to take vengeance on someone.

By the light of a palm-oil lamp the exasperated leader saw an old man lying on a pallet, green foam coming from his mouth, a look of death upon his face.

"You are good to come to my succour," gasped the Ichafian in the Tuareg dialect. "All my friends desert one who has the green plague. Will you, of your mercy, go to the physician Houama? Ask him—"

But the trio of strangers went out almost as quickly as they came in, and with a knowing smile the old Ichafian spat a fragment of soap from his mouth and wiped surplus chalk from his face, then turned to enjoy the sleep of a healthy man.

As it happened Sidi ben Baar came to Houama's cell. A warrior bearing a light preceded the leader and revealed the silent figure sitting there.

"Who are you, carrion of this cursed city?" barked the Sidi.

"Not what thou sayest," was Houama's response. "I am a physician."

The fierce leader recoiled. "Do you attend those suffering from green plague?"

The merest flicker of a smile came to Houama's eyes. "There are few to attend," he replied. "'Tis said that only one in a hundred recovers from the green plague, and he hands it on to a hundred others of whom ninety-nine—"

There was a second hurried exit; Sidi ben Baar feared no man, but who could stand against a scourge like this green plague?

Yet was the fierce leader a man not easily thwarted. "The fire-car must be found," he shouted to his followers, "and the boy of the roumis tortured till he disclose the hiding place of the salt bar marked with the crescent."

A fuzzy-haired warrior replied. "I have found a well big enough to take the fire-car. The fire-car has been hoisted over the city wall and lowered down the well which I will show you."

The Sidi and his warriors crowded after the fuzzy-haired one who had spoken. All were set on following up the slightest clue if only they might the sooner leave the uncanny city and return to the healthier atmosphere of Timbuctoo.

The fuzzy-haired warrior brought the crowding warriors to a courtyard where the biggest well in Ichaf was to be found. In his excitement to demonstrate to his questioning comrades that so big a car could descend so narrow a shaft he leaned over too far and toppled down the well.

He shot down the centre of the shaft, touching nothing till he collided with a lady of the subterranean city who listened below.

Neither the fuzzy-haired one nor the lady were seriously hurt, but the latter let forth such a howl that the Sidi and his warriors were for the moment scared out of their wits, and all but fled pell-mell.

Above, Sidi ben Baar, after his first fright, smiled in triumph; his astute brain saw in the accident the solution of his problems: the Secret of the City was out!

Below, Aa came running to hush the howling woman, and—to be seized by the fuzzy-haired warrior!

Sidi ben Baar leaned over the low parapet and demanded to know what was happening.

The fuzzy-haired one shouted back that he held the boy of the roumis captive.

But a shrill voice echoed up the shaft so that all heard: "I am Aa, the High Priest's son. Let the Sidi ben Baar descend and I will lead him to the Salt Bar he so much desires."


CHAPTER XXIII
THE TRAPPING OF SIDI BEN BAAR

STRAIGHT from the scene of the tragic mishap in the history of the Secret City beneath the sand ran Tony Mase. He had heard Aa's astounding offer.

"Yacoob! Yacoob!!" he cried, as he sighted that Ichafian. "Your nephew has promised to hand over the Salt Bar to the enemy."

"He has promised to lead the Sidi ben Baar to where the Salt Bar lies," corrected Yacoob. "One has reported to me Aa's words."

Yet, though Yacoob spoke calmly enough, he hastened forthwith to the shaft by which the enemy were entering the Secret City beneath the sand.

It said much for the courage of that treacherous wolf, Sidi ben Baar, that he was one of the first couple to descend "the well" in the bucket which grounded where the fuzzy-haired warrior held Aa prisoner. Four stalwart Ichafians, bearing lamps, stood silently watching but making no effort to rescue the High Priest's son.

"Greeting," said Aa solemnly as Sidi ben Baar stepped from the bucket. "We use no arms in Ichaf, wherefore it is no unfair thing to ask you to lay aside your weapons. Indeed no man may enter the temple where the Salt Bar lies if he carries sword or spear."

With a sly wink at the Arab who had descended with him the Sidi laid his sword aside.

Five stalwart citizens, unarmed, came hurrying up; they received the weapons of the marauders as the latter landed below. The Sidi commanded his men so to do: when he had secured the Salt Bar there would be plenty of time to regain their weapons and put the city to the sword. He had heard rumours of this tribe of Grey Tuaregs who would not fight, and he thanked his lucky stars which had brought him hither, as he thought.

"Whilst your men descend," Aa said to the Sidi, "I will go to my father and make due arrangements."

"All is well, little brother," responded the delighted leader. But he would not have said that had he known what "due arrangements" Aa contemplated.

Tony, at Yacoob's suggestion, had hurried to the temple to learn if Padaa were aware of what was afoot. But it was difficult for the English boy to find his way in the dark alleys, and before he reached the High Priest Aa had already told his father all and was gone again on the urgent business in hand.

Padaa was calm though his little world was threatened and the Salt Bar likely to be captured.

In answer to Tony's alarming report he replied: "The fiercest warrior is a fool when he cannot see. And we in Ichaf trust in Christos Who will not let the wicked triumph over us."

"But all the Sidi's men are coming down the wells," cried Tony, "and how can we escape?"

"How can they escape?" was the grave response. "At every shaft our men await to take their weapons, and presently, at a signal that Houama will make, the enemy will be in the toils."

Even as he spoke he bent and blew out the lamp upon the table of the living apartment where Tony had found him. At the same time he gave directions to his four servants, and soon every lamp in the temple and the apartments had been extinguished.

"To every house in Ichaf the order to extinguish lights has been sent; that means no great deprivation to those of us who live below," continued the High Priest, "for we can see in the dark. Within a hundred breathing-spaces all lights in Ichaf will have been extinguished except for this one here."

Padaa touched a hidden spring in the wall and a secret cupboard was revealed wherein a lamp burned steadily.

"At the second sounding of Houama's drum this lamp will be borne to the altar," declared the High Priest, "and there in the temple all the people will be gathered to witness the fate of the evil Bar of Salt."

The door of the secret cupboard swung to and Tony was in utter darkness. He stood helpless, hesitating what to do. There was a bustle about him, people coming in and out of the temple, much giving and taking of orders.

And then came Houama's signal—a dull throbbing note that sounded in every corner of the subterranean city, transmitted from that very cell above ground where Henri and Esaf were hiding.

"Now there is no light in the whole of our underground Ichaf," said the High Priest at Tony's elbow. "Seat yourself, son of the roumis, and wait till Houama drums again; then come to the temple."

It struck Tony as ridiculous to sit there so uselessly, and he recalled with a smile Padaa's remark: "The fiercest warrior is a fool when he cannot see." He thought he began to fathom how Sidi ben Baar might be foiled. It was eerie waiting there in sheer darkness, picturing all that might be happening in the subterranean city. There was a distant hubbub and a clash of arms.

It was Yacoob's voice that presently spoke in his ear. "The fight commences," announced the Grey Tuareg with a note of humour in his usually solemn voice.

There came the sound of stumbling in the street without and a volley of oaths in the Arab tongue. Then came a hammering of fists on a bolted door, the sound of a shot, the rush of many feet.

Tony shivered with apprehension, not so much for himself as for the unarmed citizens without. Yet, as he listened, it was the voice of the raiders that rose in protest, anger and surprise.

The clamour increased, the sounds of confusion were redoubled, the laments of the marauders grew more predominant.

Yacoob audibly chuckled. "The Sidi cannot see, but our people can," he said.

"You can slaughter the lot like sheep," said the war-minded Tony.

"We of the Secret City do not murder," Yacoob said in tones of reproof. "We who follow Christos may not kill."

"Then what's going to happen?" asked the English boy. "Surely it would be well to wipe out a murderous gang such as that of the Sidi ben Baar?"

"Not so taught Christos," Yacoob said reverently. "But, listen, there is much fun afoot."

"Fun!" cried an incredulous Englishman.

"Assuredly!" responded Yacoob. "I can hear our invaders cry for quarter, vowing their swords have been snatched from them."

"But they should have no swords. The High Priest told me they were required to deliver them up."

"When the lights went out the raiders snatched at the weapons lying on the ground, white stranger," answered Yacoob. "But soon we shall have flung them all into the river."

"So you are drowning the Sidi and his men," said an unthinking English boy.

"No, white stranger; will you never learn?" said Yacoob severely. "It is the weapons we fling into the river. But, come, let us venture forth and see what's afoot."

The hubbub had died out in the distance. Yacoob caught hold of Tony's arm and led him forth into the street.

"'See what's afoot!'" repeated Tony indignantly as he stepped along in the inky darkness. The English boy was no better than a blind man, but the Grey Tuareg walked confidently, for he could see in the dark with those shining yellow eyes of his.

Suddenly Tony stumbled over a prone body. Yacoob was watching an Ichafian filch the spear of an Arab.

Yacoob clutched at the falling Englishman and saw the Black Tuareg, his enemy, lying on the ground.

"It is one of the Sidi's men," Yacoob said as he knelt. "He has smitten his head against the wall and knocked himself senseless. There is blood welling from a wound in his head."

In the pitch darkness Tony could see nothing and could render no help. He heard the tearing of a robe, and understood that the Grey Tuareg was binding up his enemy's hurt.

Fending off a furious warrior who had run amuck, Yacoob helped the wounded man to his feet.

The half-conscious raider clung to Yacoob's left arm, Tony clung to Yacoob's right. They had difficulty in avoiding the panic-stricken men rushing blindly through the darkness, but at length Yacoob left his foe in a surgery, where sick men were treated.

Cries of alarm, shouts of rage and vows of vengeance came from the raiders, but there was no response from the silent defenders of the Secret City. But weapons were filched from the warriors and flung into the river, and refractory raiders were seized and trussed up with rope—to be bundled off to the temple, where all underground Ichaf manhood was gathering.

Tony heard a yell of surprise from a man in pain. Yacoob told the English boy that the Sidi ben Baar had suddenly grappled with a man whom he took for an Ichafian, but who was an expert swordsman of his own band. And the swordsman thought he had found a foe in whom he could sheath his sword at last.

The two raiders grappled, and there was a furious contest, from which the watching citizens perforce must stand aside. The Sidi bore a spear and presently broke loose from the swordsman's grip. And then it was a contest of spear against sword, with neither combatant knowing where his rival stood. And the spear won!

It was the only death in Ichaf that night.

Sidi ben Baar had transfixed his chief swordsman, but before he was slain the swordsman had sliced off two of the Sidi's fingers.

And thereupon the Sidi, crashing over a handcart in the road, was made prisoner, and was borne, suitably trussed, to the great concourse of people gathering in the temple, where his fingers were dressed.

It was a strange crowd in the dark temple, where Tony could see nothing, but hear much!

Sidi ben Baar's force had been utterly overcome in the darkness without the aid of a single weapon—unless the broom wielded by the old woman be reckoned as weapon!

Many of the warriors were deposited on the temple floor like bales of merchandise, but some were whimpering like frightened children in the darkness, clinging to their captors. Not one of the warriors, however, bore a weapon, all arms had been flung like garbage into the river.

The temple, a huge building, was crammed to its limits, though no women or children of Ichaf were present. About the altar stood a circle of white-robed youths of stalwart build who linked arms and kept back the press of people and prisoners.

Into this living circle, from the nearby apartments of the High Priest, came Aa bearing a lamp, and never was light so welcome to Tony.

The small boy placed the lamp upon the altar so that it shone on the White Cross above and the Salt Bar alongside.

Aa then took a seat on the altar steps and his father came forth to be welcomed with the Sign of the Cross.

Following Padaa came Yacoob, bearing an axe across his shoulder.

"Listen, all of ye," said the High Priest in the Tuareg tongue, familiar to all except Tony, "and learn wisdom ye evil ones who thought to wage war on our Sacred City."

Sidi ben Baar broke forth into foul revilings.

"Gag the blasphemer," said the High Priest solemnly.

The bound man had an oily rag thrust into his mouth and secured with a turban. It served not only to silence him, but others of his followers who saw the uselessness of protesting.

"Know, all of ye, that the men of War shall ultimately perish," came the resounding voice of the High Priest; "that the men of Peace shall conquer the world at length. The Christos Whom we worship said it two thousand years ago, and though 'tis long in coming, we know His words must come true. As a symbol how the things of War shall perish my brother Yacoob shall wield his axe on this evil thing within the Salt Bar."

The Salt Bar was lifted from off the altar and placed upon the ground.

High above his head Yacoob lifted his axe, then brought it down athwart the coveted Salt Bar.

The bar split in twain and a leather amulet fell out amidst the salt. There was a tense silence followed by a hum of voices. Such of the raiders who were free of bonds fell in adoration. For it was the historic amulet that the Mahdi had worn when he conquered General Gordon at Khartoum and drove the English from the Soudan—so the desert men said.

Soon groans of indignation, growls of resentment, whimpers of superstitious fear arose from the trussed captives, but on the faces of the Ichafians was a great contentment. This barbaric emblem, said the Grey Tuaregs, should never again foment war in the desert lands, never again be worshipped in secret by the sons of the desert from the time it was taken from the Mahdi's tomb till it fell into the hands of the villain Jambonne, whose attempt to foment another Jehad had been frustrated by their High Priest and his son Aa.

Padaa bent and picked up the discredited emblem flung at his feet by Yacoob. He tore the rotting amulet across.

"Thus shall the emblems of War be destroyed," cried the High Priest. "Men of blood have sought to use this amulet to sow the Sahara with the bodies of foolish fighters. Sidi ben Baar thought to brandish this relic of the Mahdi on high and so draw to himself all the Tuareg of the Sahara and the Soudan—all the warring savages who would make common cause and drive the roumis into the sea. Without this amulet the various tribes would not unite under his banner, and now—"

The High Priest, his followers making a lane for him in the thronged temple, strode to the parapet above the swift-flowing river clutching the torn amulet in his fist.

"And now," he repeated, "I fling this cursed emblem of evil war to the underground river where it will be lost for ever and ever."

Sidi ben Baar, bound and gagged, struggled to a sitting posture, his eyes rolling in his head, the veins in his temples standing out like cords; he was beside himself with rage and mortification as he saw the amulet disappear—that amulet which was to have vested him with godlike power—that amulet which was to give him victory over all his enemies!

The thwarted villain made an effort to rise, then slumped to the ground, his eyes staring glassily out of his empurpled face.

"He is stricken of Allah!" cried the High Priest, returning to the altar. "Bear him and his followers to the surface. There let them be set on their steeds that they return whence they came. And let the Peace of Allah, which His Son Christos came to preach, rest again upon our sacred city of Ichaf!"


CHAPTER XXIV
FAREWELL TO THE SACRED CITY

IN the house of Houama, on the city wall of Ichaf, Henri and Esaf waited, forbidden to go forth by the magician. Houama had flung off his first paroxysm of terror and, in communication with another telepathist in the subterranean city, was concentrating all his powers to frustrate the Sidi ben Baar and his followers.

"Say no word, Capitaine Leprince," begged Esaf, when Henri would have made frantic enquiries after his cousin, "lest we divert Houama's thoughts and ruin all."

The waiting and doing nothing was a trying ordeal for the volatile French youth; and even Esaf, after a time, could not restrain Henri from getting up from his seat and opening the door cautiously.

Houama turned on him, blinking like one who awakes from a dream. "You go forth to your death, fool," he said angrily, "and bring the raiders to our refuge. The warriors of the Sidi stand armed at the mouth of every well, and you cannot descend."

"I am in Tuareg disguise," protested Henri, closing the door however, for the eyes of Houama had some strange compelling power in them. "I can deceive the raiders in the darkness and descend to my cousin's rescue."

"You—will—sit—down," said Houama, slowly and distinctly, in the French tongue.

And like a naughty boy Henri returned to his stone bench, sitting there motionless till the grey of dawn crept into that strange chamber.

It was Esaf's hand that touched Henri's knee and Esaf's finger that pointed upward expressing caution and attention.

A dull, thrumming noise filled the air, momentarily growing more insistent. Even Houama seemed puzzled and disturbed.

To Henri the insistent noise was no puzzle. "It's a 'plane," he cried, and this time nothing could prevent him rushing forth to gaze upward into the sky.

There, catching the light of the dawn, hung an aeroplane over the Secret City. Never before had an aerial visitor flown above Ichaf, and it was causing consternation amongst the sentries at the shafts.

"A torch! A lighted torch!" cried Henri, poking his head into Houama's cell. "There's a French military aeroplane threatening Ichaf."

Houama was looking radiant; he had received a communication from his colleague below; the invaders were being bundled out of the subterranean city a terrified mob.

Houama himself ran forth with a flaming torch, handing it to Henri, who stood on the salt wall looking down into the moat.

Henri flung the flaming torch into the moat, where it flared up and showed the pilot of the 'plane where there was safe landing.

The flying machine made a perfect pancake landing.

Henri ran toward the 'plane—a four-seater with two occupants.

A man jumped out from the observer's cockpit, having noticed Henri lower himself from the city wall by the hidden rope.

The arrival from the air was in airman's uniform and—had a crooked nose. He saluted as Henri ran up. "Accept my apology for not keeping the appointment in your rose arbour, Monsieur Henri Leprince."

Henri bowed. "You are of the French Secret Service, monsieur?"

The man with the crooked nose nodded. "It is owing to the attention of the villain Jambonne that I did not make the acquaintance of so gallant a motorist at an earlier date."

"My cousin said you were the man who was carried into the Villa Agadaas. Did Jambonne waylay you, monsieur?"

"His ruffians did, for I knew too much," responded the man with the crooked nose. "I knew there was unrest amongst the Tuaregs of the Sahara and the Arab malcontents of Timbuctoo, and was working on a clue that implicated Gaston Jambonne. I guessed that he was using your Crimson Caterpillar to further his evil designs. By the time I escaped from the Villa you were motoring south and were bearing some banner or relic which would inflame the Moslems of the desert to revolt against the French. A native calling himself a Grey Tuareg gave me the information; but, though by telegraph and wireless I communicated with the French authorities in Touggourt, Ouargla and Timbuctoo, I secured no proof that you carried such an emblem. Such information, however, coincided with certain facts which I had gleaned, so I secured this 'plane, and from information gained from a certain Amadhou followed you hither. I was told that here a certain Sidi ben Baar would raise the standard of revolt, but I see no armed force and only a few sentries guarding a zareba outside a deserted city."

"The drama is being played out in the city beneath the sand," declared Henri, and proceeded to acquaint the Secret Service man with such facts as had been gathered.

Before the French youth had done speaking there came a sudden stir of life in the hitherto silent city. Out from the crawling-hole into the moat scrambled scared warriors and trussed captives anxious only to put a distance between themselves and the uncanny city below the sand.

"Flight!" was now the one cry of the raiders who only a few hours before had been confident of victory.

A speechless Sidi ben Baar had been hauled to the surface, his tongue and right side refusing to do their offices; his brain was active enough, and he pointed across the desert with his left hand—away back to Timbuctoo, anywhere as long as he turned his back on the accursed city.

"Flight! Flight!!" was counselled on every hand by the raiders who had been converted into bales of uselessness by unarmed, pallid ghosts of an underworld.

"Flight! Flight!!" cried Black Tuareg and Arab alike as they streamed back to their zareba.

"Flight! Flight!!" cried the raiders as they rushed to their camels and horses, wondering at the gifts of dried dates pressed upon them by the Grey Tuaregs they had planned to exterminate.

"Flight! Flight!!" rang the cry through the zareba; for the Mahdi's amulet, which would have led a fanatical army to victory, was lost for ever and their chief was stricken of Allah.

The crash of those ascending the wells prevented Henri descending to find his cousin. The Grey Tuaregs needed no buckets to bring them to the surface, they scrambled like monkeys up the shafts.

At length the cousins sighted each other. Tony held out a hand, but Henri gathered his cousin into a close embrace and kissed him on both cheeks.

"Jolly glad to see you," remarked the matter-of-fact English boy, "but do you know you're treading on my toes?" And Tony gently disengaged himself from Henri's Gallic hug.

"Pardon," said Henri, and then in sudden alarm: "What of ma chère Caterpillar?"

"Let's go and see," said Tony, and signalled to Yacoob who stood close by.

With difficulty they passed through the mob about the second crawling-hole and came to the sand dunes adjoining the raiders' zareba.

"See! Sidi ben Baar is strapped to a camel and is fleeing with his host in a sauve qui peut," cried Henri, pointing to the tail of a struggling caravan bolting panic-stricken across the desert.

Yacoob was already superintending the exertions of a body of Grey Tuaregs with spades. The Ichafians were digging into what looked like an arm of the sand dune.

"Ma chère Caterpillar is bound to win through," Henri murmured, but watched with anxious eyes as he realised she had been buried in sand.

Between sand and car, however, had been placed big mats of close-woven vegetable fibre which had prevented the sand from penetrating to any serious extent.

"There's a day's work to put in on the old bus," declared Tony, when at length the Crimson Caterpillar stood revealed.

"Ma chère Caterpillar is worth a week's cleaning," said her proud owner, as he patted the crimson enamel of her bonnet. "And, although our friend of the Secret Service would carry us back to Algiers in his 'plane, I shan't desert our gallant car."

"Of course not!" agreed Tony.

It was the Crimson Caterpillar therefore which bore the cousins back across the desert, though they were glad to accept the offer of petrol from the flying men who had flown to their assistance.

Aa's serious little face frowned them off, and Yacoob and Esaf were with him to wave a farewell as the Crimson Caterpillar set off from the Secret City, the aeroplane overhead as a flying escort.


Illustration

The return, shepherded by the 'plane, was without incident, except for constant enquiries from fierce warriors concerning the price of capsicums.

"Capsicums will not be on the market by March the Eighth," was Henri's emphatic response to all these fanatics. He realised that the message Sidi ben Baar had been so anxious for him to deliver on his return journey was no less than a declaration of war in the Sahara and Soudan—a war frustrated by the destruction of the Mahdi's amulet.

All that the cousins brought back from the City beneath the Sand was the golden goblet given to Tony by Padaa; but Tony was telling me recently that the High Priest offered him as much of the temple treasure as he liked to take away, saying that it was mere lumber, vastly inferior to salt.

Gaston Jambonne's further payment, as promised to Henri, was never made. That villainous trader was found guilty of the assault on the man with the crooked nose, of traitorous dealings with the Tuareg tribes, and was condemned to a long term of imprisonment.

The cousins, however, through the exertions of the Secret Service man, were awarded a handsome cheque from the French authorities, who declared that Henri and Tony had averted a revolt in the desert.

But Tony asserts that Aa should have had all the credit.


THE END


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