At the end of their next day's journey the Trail began to swing away from the jungle, and thereafter led ever upward, skirting the foot-hills of the mountain-ranges beyond which lay the lost cities of the Incas. Three days after Will's escape from the pit he found himself once more in terrible danger. During the siesta period at noon he had walked away from the rest of the party to see what new birds he might find. Not far from the camping-spot he came to a place where a colony of crested black-and-gold orioles had built long, hanging nests of moss and fiber among the branches of a low tree.

Curious to see whether their eggs looked like the scrawled and spotted ones of the Northern orioles, Will started to climb the tree. Before he was half-way to the nests, a cloud of clamoring birds were flying around his head, and as he looked up he noticed for the first time, directly above him, a great gray wasps' nest. Even as he looked, one of the circling birds brushed against it, and a cloud of enormous red wasps poured out. They paid no attention whatever to the birds, but flew down toward Will, who was already scrambling out of the tree at full speed.

Even as he reached the ground, two of the wasps settled on his bare arm, and instantly he felt as if he had been stabbed by red-hot daggers. Never in his life had the boy known such agony. Trembling with pain, he brushed the fierce insects off and rushed at top speed toward the camp. In spite of the heat, a racking chill seized him as he ran. His teeth chattered together and waves of nausea seemed to run over his whole body, dimming his eyes and making his head swim He just managed to reach the rest of the party when he staggered and fell.

"I've been stung by some big red hornets," he murmured, and dropped back unconscious.

"It's the maribundi wasp," said Professor Ditson, looking very grave as he helped Hen undress the boy and sponge his tortured body with cold water. "Three of their stings have been known to kill a man."

By evening Will was delirious. All night long Hen and the scientist worked over him, and by the next day he was out of danger, although still in great pain and very weak. It was several days before he could walk, and then only with the greatest difficulty. At first every step was an agony; but Professor Ditson assured him that regular exercise was the best way to free his system from the effect of the maribundi venom.

Once again death which had dogged the adventurers' trail for so long peered out at them. They had finished the first stage of their day's walk, and Will was lying white and sick under a tree, trying to gain strength enough to go on. Ahead of them stretched a wide river, with a ford showing, down to which the Trail led. Suddenly from the depths of the near-by jungle came a horrid scream, followed by a chorus of baying notes something between the barking of a dog and the howl of a wolf. As the travelers sprang to their feet, a shower of blood-red arrows, with saw-edged points and barbs fashioned from flinty strips of palm-wood, dropped all around them. Again the wailing, terrible cry broke the silence.

"It's the jaguar-scream—the war-cry of the Miranhas," said Professor Ditson quietly. "They are on our trail with one of their packs of wild dogs."

Even as he spoke, from the forest far below them a band of Indians broke into the open. Ahead of them raced a pack of tawny brown dogs nearly as large as the timber-wolves of the North.

Hen unsheathed his great machete, while Jud fumbled with the holster of his automatic.

"No! no!" said Professor Ditson sharply. "We can stand them off better across the river. Hurry!"

Without a word, Hen picked up Will's limp body and raced ahead of the others around a bend in the trail which hid them all for a moment from the sight of their pursuers. At the river the scientist suddenly halted, after a long look at the rapids which ran deep and swift on each side of the ford.

"Don't splash as you go through," he said quietly. "I'll come last."

One by one, the little party, headed by Hen with Will in his arms, waded carefully through the shallow water. As they went Jud thought that he caught glimpses in the river of the squat, fierce forms of the dreaded piranhas, but if they were there they paid no attention to the men, who crossed with the utmost care. Just as Professor Ditson, the last of the party to leave the bank, stepped into the stream, there sounded with startling distinctness the same wild chorus which had come from the jungle. Once or twice in a life-time a hunter in South American forests hears the fearsome screech which a jaguar gives when it is fighting for its life or its mate. It was this never-to-be-forgotten sound which the Miranhas had adopted for their war-cry.

Down the slope not three hundred yards away came the hunting pack. Right behind them, running nearly as fast as they, raced a band of some fifty Miranhas warriors. As the fugitives looked back it was not the nearness of the wild-beast pack nor the fierce band of Indian warriors rushing down upon them which struck the color from the faces of Will and Joe. It was the towering figure of a man with a black bar of joined eyebrows across his forehead and a scar on his cheek which twisted his face into a fixed, malignant grin.

"Scar Dawson!" muttered Will.

"Scar Dawson!" echoed Joe, despairingly.

As they spoke the outlaw seemed to recognize them too, for he waved aloft a Miranha bow which he carried, and shouted hoarsely. By the time they reached the other bank, Will lay half-fainting in Hen's arms.

"Fellows," he whispered, "I'm all in. Hide me in the bushes here, and you go on. There's no sense in all of you sacrificing yourselves for me."

"We stay," murmured Joe, while Hen nodded his head and Pinto fitted one of his fatal little arrows into his blow-gun.

"Sure, we'll stay," chimed in Jud, unslinging his automatic, "an' there's seven Injuns who'll stay too unless I've forgotten how to shoot. But what in the world's the perfesser doin'?" he went on, peering out over the river.

Unheeding the tumult of howls and screeches behind him, or the rush of the fierce hounds and fiercer men toward him, the eminent scientist was picking his way carefully through the ford. At the middle of the river, where the water ran deepest, he rolled up his left sleeve, and with his hunting-knife unconcernedly made a shallow gash through the skin of his lean, muscular forearm. As the blood followed the blade he let it drip into the running water, moving forward at the same time with long, swift strides. Almost in a moment the river below the ford began to bubble and boil with the same rush of the fatal hordes which had so horrified Jud and Will at the Lake of the Man-eaters. As Professor Ditson sprang from the water to the edge of the farther bank, the water clear across the river seemed alive with piranhas. Unmoved, he turned to the rest of the party.

"That ford is locked," he said precisely. "For three hours it can not be crossed by man or beast."

Even as he spoke, the wild-dog pack splashed into the river. As they reached the deeper water and began to swim, the flash of hundreds of yellow-and-white fish showed ahead of them. In an instant the water bubbled like a caldron gleaming with myriads of razor-edged teeth. There was a chorus of dreadful howls as, one by one, the fierce dogs of the jungle sank below the surface, stripped skeletons almost before their bodies reached the bottom of the river. From the farther bank came a chorus of wailing cries as the warparty watched the fate of their man-hunting pack. Then, as if at some signal, the whole band threw themselves on their backs on the ground. Only the towering figure of the giant outlaw remained erect.

"What's happened to those chaps?" queried Jud, much perplexed. "I've been with Injuns nigh on to forty year, but I never see a war-party act that way."

As he spoke, Professor Ditson reached the summit of the slope where the rest of the party were standing, and saw the prostrate band on the other side of the river.

"Hurry out of here!" he said sharply, racing around a bend in the trail, followed by the others.

Their retreat was none too soon. Even as they started, each of the men of their far-away pursuers braced both his feet expertly against the inside horn of his bow, and fitting a five-foot arrow on the string, pulled with all the leverage of arms and legs combined, until each arrow was drawn nearly to its barbed point. There was a deep, vibrating twang that could be heard clearly across the river, and into the sky shot a flight of roving shafts. Up and up they went until they disappeared from sight, only to come whizzing down again from a seemingly empty sky, with such force and accuracy that they buried themselves deep into the ground just where the fugitives had been a minute before.

Jud, who had lingered behind the others, had a narrow escape from being struck by one of the long shafts.

"We'd have all looked like porcupines if we'd stayed there thirty seconds longer," he remarked to Joe, as he joined the rest of the party. "Them Miranhas are sure the dandy shots with a bow."

"Huh!" returned Joe jealously, "that nothing. My uncle out in Akotan, where I come from, he kill a man with an arrow half a mile away, and no use his feet either."

"That uncle of yours was some performer with a bow," returned Jud cautiously. "Half a mile is good shootin' even with a rifle."

"Some performer is right," chimed in Will weakly. "I learned long ago, when Joe and I were up by Wizard Pond, that that uncle of his held a world record in everything."

"Set me down, Hen," he went on. "I think I can do a mile or so on my own legs."

"From here on Pinto and I have been over this route," announced Professor Ditson. "Ten miles farther on is 'Sky Bridge.' If we can cross that and cut it behind us, we're safe."

Two by two, the members of the party took turns in helping Will along the Trail, which soon widened into a stone-paved road.

"This is one of the Inca highways," explained the scientist. "It leads from their first city clear to the edge of the jungle. Once," he went on, "the Incas ruled an empire of over a million square miles, equal to the whole United States east of the Mississippi River; but they never were able to conquer the jungle."

The road sloped up more and more steeply, and the going became increasingly difficult, but Professor Ditson hurried them on remorselessly.

"The Miranhas never give up a chase," he said, "and if they have succeeded in crossing the river above or below the ford, they may even now be hard on our heels."

Before long they were in a wilderness of bare, stern peaks whose snow-covered summits towered high against the horizon. At times the road zigzagged along narrow shelves cut in the faces of precipices and guarded here and there by low retaining-walls built of cut stones laid without mortar, but so perfectly that the blade of a knife could not be thrust between them. The air became colder, and the scientist told them that often the temperature in these mountain-valleys would vary as much as one hundred degrees within twenty-four hours.

As they approached the crest of a great ridge which towered above them, Jud began to find great difficulty in breathing and complained of nausea and a feeling of suffocation.

"It's the soroche, the mountain-sickness," explained Professor Ditson. "It will pass soon."

"I'm the one that's goin' to pass—pass out," panted Jud.

Soon he became so exhausted that, like Will, he had to be half-carried along the trail.

"You an' me are a fine pair to fight Injuns," he whispered to the boy, who smiled wanly in reply.

Beyond the ridge the road ran downward toward a vast gorge. From its dark depths rose and fell at intervals the hoarse, roaring bellow of a river rushing among the rocks a thousand feet below.

"It is Apurinac, the Great Speaker," said Pinto.

As the trail led downward again, Jud began to feel better, and before long he was able to walk without any help.

At length, far below them, looking like a white thread against the threatening blackness of the caÑon, they saw swinging in the wind a rude suspension bridge of the kind which travelers had used in these mountains ever since the days of the Incas. When Pinto, who knew the bridge well, learned that Professor Ditson intended to cross it at once, he was much disturbed.

"No one, Master," he protested, "ever crosses it except at dawn before the wind comes up; nor should more than one at a time pass over it."

"To-day," returned the scientist grimly, "you are going to see six men cross this bridge in the middle of the afternoon, wind or no wind; and what's more, they are all going to cross together." And he waved his hand toward the road along which they had come.

Against the white side of the mountain which the trail skirted showed a series of moving black dots, while down the wind, faint and far away, came the tiger-scream of the Miranhas. They had found a way across the river, and once more were hard on the heels of the treasure-hunters.

Along the Inca road the little party hurried at breakneck speed. At one place it ran between a vertical wall of rock and a dizzy precipice. Farther on it led down by rude stairs partly cut in the rock and partly built out of stones. At one point it made a sudden turn with a low parapet built around it in a semicircle to keep descending travelers from slipping off into the depths below from their own momentum. Once beyond this last danger-point, the fugitives found themselves before Sky Bridge itself.

So deep was the caÑon that from the river a thousand feet below the bridge seemed on a level with the clouds and to deserve well its name. It was made of two thick cables, woven out of braided withes, which stretched nearly a hundred yards from bank to bank of the gorge. Between and below these ran several smaller cables, fastened to the upper two, which served as guard-rails. Sections of cane and bamboo laid transversely across the three lower cables, and tied on by strips of rawhide, formed the flooring, which swung four or five feet below the upper cables.

From far below came the stern roar of the Speaker, and at the bottom of the sunless gulf gleamed the white foam of the river as it raged against masses of rent and splintered stone. Over the abyss the bridge waved back and forth in the gusts which all day long swept through the gorge. At times, when the frail structure caught the full force of the wind, it swung fully ten feet out beyond its center, hung a second, and then dropped back with a jar that threatened to snap the cables or hurl into the abyss any human being who was crossing the bridge.

Not for all the treasure of the Incas would any one of the party have risked the crossing. The fear of death, however, is a great incentive to brave deeds.

"I'll go first," said Professor Ditson suddenly, "and see if it is possible to get over. Unless we cross this bridge within the next fifteen minutes, we're all dead men."

Without further speaking, the scientist stepped out upon the swaying bridge and gripped the twisted cables firmly fixed in buttresses of stone. At first he shuffled along with short, cautious steps. In front of him the footway of bamboo strips sloped away sharply clear down to the swaying center of the bridge. From far below, up through the mists which half hid the river, soared a bird the size of a pigeon. As it circled up through a thousand feet of space, it seemed to grow and grow until, by the time it reached the level of the bridge, rocking on mighty motionless wings, it showed itself as the great condor of the Andes, the second largest bird that flies. From its grim, naked head its cold eyes gazed evilly upon the man clinging to the swaying bridge, and then turned toward the little group huddled against the side of the precipice, as if counting them as additions to its larder of death. As the great vulture swept by, blotting out a stretch of sky as it passed, the wind hissed and sang through the quills of its enormous wings, taut and stiff as steel. Rocking, swaying, perfectly balanced in the rush of air that howled down the caÑon, the bird circled over the bridge, and then, without a flap of its vast wings, dipped down into the depths below until, dwindling as it went, it disappeared in the spray of the prisoned river. To the travelers, no other sight could so have plumbed the depths that lay beneath the bridge. For a moment the scientist, sick and giddy, clung to the swaying cables which seemed to stretch tenuous as cobwebs across the sheer blackness of the abyss.

"Come back, Master," called Pinto. "No man can cross that bridge!"

"No man here will live who doesn't cross this bridge," returned the professor, as the wind brought again to their ears the war-cry of the Miranhas.

Bending double and clinging desperately to the ropes woven from tough maguey fiber, he edged his way down the swaying slope, while the others watched him as if fascinated. At times the full force of the wind as it was sucked through the long caÑon swung the bridge out so far that he had to lie flat and cling for his very life's sake. When, at last, he reached the lowest part of the curve, instead of climbing up to the safety of the opposite shore, the scientist deliberately turned around and, taking advantage of every lull and pause in the sudden gusts which bore down upon him, began the long steep, slippery climb back to the point from which he had started.

"He's riskin' his life twice to show us the way," said old Jud, suddenly. "Come on! I'm more ashamed to stay than I'm scared to cross."

Foot by foot, clinging desperately to the sagging, straining cables, Professor Ditson fought his way back. When at last he regained the safety of the cliff-side, his face was white and drawn, and he was dripping with sweat, while his hands were bleeding from the chafing of the ropes; but there was a compelling gleam in his eyes, and his voice, when he spoke, was as precise and level as ever.

"I have proved that it is perfectly possible to go over this bridge in safety, and I believe that the cables are strong enough to hold the weight of us all," he said. "I will go first; Hen will go last. Don't look down. Hang on. Watch the man ahead, keep on going, and we'll get over—just in time."

He stretched his gaunt arm toward the trail, where now the Miranha band was in plain sight not half a mile away!

Again he turned and started out over the bridge, which swayed and swung above the death that roared far below. Without a word, but with teeth clinched grimly, Jud tottered after him, his long gray beard blowing in the wind. Next came Pinto, shaking with fright, but with a habit of obedience to his master stronger than his own conviction that he was going to his doom. Joe followed; and between him and Hen, who brought up the rear, was Will. As the full force of the wind struck the swinging structure, now loaded with their united weight, the taut cables and ropes creaked and groaned ominously, while now and again some weakened fiber would snap with a sudden report like a pistol-shot.

Down and down the first terrible incline crept the little train of desperate men. There were times when the bridge would swing so far out that only by clinging and clawing desperately at the guard-rope could the travelers keep from being tipped into the depths below. When that happened, each would grip the one next to him and, with linked arms and legs, they would make a human chain which gave and swung and held like the bridge itself. At last they reached the low-swung center of the bridge, and caught the full force of the wind, which howled down the gorge like a wolf. For a long minute they lay flat on their faces as the bridge swung forth and back like a pendulum.

As the gust passed, they heard close at hand the tiger-screech of the Miranhas rushing at headlong speed down the trail as they saw their prey once again escaping. Up the farther slope, crouching low and gripping desperately with twining hands and feet, the fugitives pressed on foot by foot. At the worst places Will felt Hen's mighty arms holding him tight to the swinging ropes, while from ahead Joe risked his life time and again to stretch out a helping hand to his friend.

By inches, by feet, by yards, they wormed their way up, until Professor Ditson was able to get a firm foothold on the side of the cliff, where a narrow path had been cut in the living rock. Even as he struggled to his feet, the war-party dashed around the sharp curve that led to the entrance of the bridge.

With all their courage and relentless vindictiveness, the Miranha band yet hesitated to cross where the white men had gone. As Jud and Pinto joined Professor Ditson on the little platform of rock which towered above the caÑon, they saw their pursuers actually turn their heads away from the deep that opened at their feet, after one glance along the narrow swaying bridge by which alone it could be crossed. Then, with a fierce yell, they dropped their bows and, whipping out long, narrow-bladed knives from their belts, fell like furies upon the tough woven cables anchored among the rocks. It was Jud who first realized that they were trying to cut the bridge.

"Hurry for your life!" he called down to Joe, who, holding on to Will with one hand, was slowly hauling himself up the last few feet of the steep ascent. Even as he spoke, the taut cables began to quiver and sing like violin-strings transmitting with fatal clearness every cut and slash and chop of the destroyers at the other end. Will was half-fainting with the strain of the crossing, which his weakened body was not fitted to endure long. Jud's shout seemed to pierce the mist of unconsciousness which was slowly closing over his head, and he struggled upward with all his might.

In another minute Joe was near enough to be reached by the party on the landing, and three pairs of sinewy arms gripped him and pulled him upward, clinging to Will as he rose. Below him, Hen, bracing both feet, heaved the boy upward with the full force of his mighty arms. Just as Will reached the refuge of the cliff, with an ominous snapping noise the bridge began to sag and drop. Hen gave a desperate spring and wound one arm around a little pinnacle of rock which stood as a hawser-post for one of the cables, while Pinto and Joe gripped his other arm in mid-air, and pulled him to safety just as the far end of the bridge swished through the air under the knife-strokes of the Indians!

As, doubled by its drop, the full weight of the structure fell upon the strained cables, they snapped like threads and cables, ropes and footway rushed down into the abyss with a hissing roar which died away in the dim depths a thousand feet below.