Presently Uncle Brian rejoined his nephew. The flying-boat was now at an altitude of 4000 metres and following the course of the Rio del Morte.
From the island from which they had made their escape rifle bullets were singing harmlessly, for the searchers, upon hearing the hum of the flying-boat's engines, had jumped to the conclusion—a correct one in this case—that the "English dogs" had scored rather heavily.
"She's well stocked in the food department," reported Uncle Brian, "and there's plenty of fuel in the tanks. With reasonable luck we'll cross the Sierras before sunset."
"And then——?"
"Make for Trinidad or Barbadoes," replied Peter's uncle, as he carefully stowed the haversack containing the secret-rays parts into a locker. "She'll do that easily. But I've a notion that I'd like to stop and have a look at the pipe-line between El Toro and Tajeco. We might be able to cut off the fuel supply to the Rioguayan Air Fleet."
"Right-o," agreed Peter. "And what about Antonio?"
"Who?" asked his uncle.
"Antonio, our mechanic," explained Peter, indicating the closed hatchway, underneath which the Rioguayan engineer was quaking and trembling. "He'll be a bit of a nuisance on board, although he hasn't the pluck of a mouse. Can't we land him somewhere? Between us we can manage quite all right."
There was no difficulty in conversation. With the plate glass window in front of the pilot's seat and the hatch to the motor-room closed, the compartment was practically cut off, both from external and internal noises. Except for the muffled pulsations of the motors and the subdued roar from the propellers, there was little to indicate that the flying-boat was cutting through the air at eighty-five miles an hour.
"It's a jolly lucky thing we didn't carry on in the motor-boat," remarked Peter. "Look down there."
He pointed to the sinuous course of the river. Even at that height it was quite easy to see that the Rio del Morte above the lake was not easily navigable. There were rapids at about every half-mile, the foaming water showing up distinctly in the strong sunlight. It was doubtful whether a small boat, or any boat, could force her way against that furious torrent, rendered even more formidable by the numerous rocks that split the swiftly-running water into dangerous cascades.
"Yes," agreed Uncle Brian gravely, "we did theright thing. But don't forget—more than likely the air station at San Antonio is in touch with us by means of the magnetic detectors. We've got to bear in mind the possibility of being pursued."
"But they won't know what has happened," said Peter. "All they know is that the 'bus is proceeding up-country, following the course of the river. They would naturally conclude that the original crew are in pursuit of our late and unlamented 'egg-box'. Until the air station people get to hear from the fellows we left on the island—by the by, what will happen to them?"
"That's not our affair now," replied Uncle Brian. "In a few days another flying-boat will be dispatched to look for them. They've plenty of water, so they won't be thirsty; and, if they're hungry—well, there's the hound. In a way, he is responsible for their present plight."
"Talking of hunger," observed Peter, "isn't it about time we piped to dinner? I think I heard a suggestion about grub a couple of hours ago."
His uncle agreed, and went aft to the store and provision room. A few minutes later, thanks to the stabilizing device that enabled the flying-boat to hold on her course both as regards altitude and direction, Peter and Uncle Brian were enjoying a plain but satisfying meal of the food originally intended for the ill-fated Rioguayan captain.
Nor was the motor-mechanic neglected, although, when Peter opened the trap-hatch to pass the fooddown to him, he cowered and trembled in a state of utter funk.
"Now," remarked Uncle Brian, after consulting a map, "we ought to be approaching the scene of preliminary operations. The pipe-line should be about here, running in a north-west to south-east direction. It may be overgrown with tropical growth, but I know for a fact that it was laid on the surface and not buried."
"Bad system, that," observed Peter.
"Yes; but it was for economical reasons," continued his uncle. "Apparently the Rioguayan authorities never contemplated an attempt to cut it. We'll do our utmost to prove the fallacy of their belief in its immunity."
By the aid of binoculars, the track of the huge oil-pipe was located. So far so good; but there still remained the task of finding a suitable landing-ground. The flying-boat, although provided with means for alighting both on the water and on land, could not reasonably be expected to come to rest on tree-tops without the almost certain risk of being completely destroyed.
At two hundred metres the aircraft followed the line—until Peter discovered a possible landing in a clearing about fifty yards from the Englishman's objective. Here, for the first time since leaving the island, they saw signs of human habitation—smalladobehuts.
"All right, I suppose?" asked Peter.
"Yes, they're Indians in the pay of the RioguayanGovernment," replied Uncle Brian. "They are paid, I understand, not for the work they do, but for the damage they don't do—sort of retaining fee, providing they are good and don't start carving pieces out of the iron pipe."
"I see," remarked Peter. "Then, as far as we are concerned, they need not be taken into account. S'pose they won't carve up our engineer bird when we set him ashore?"
"They will more likely take him down to El Toro and get paid for the job," said Uncle Brian.
His nephew nodded. He was now engaged upon the task of bringing the flying-boat to earth, no easy task in a strange 'bus and on a landing-ground of doubtful quality and very limited extent.
With a succession of slight jolts, the flying-boat was brought to rest with her nose within ten feet of one of the huts. No Indians came out to gaze curiously at the wonderful sight, or to beg tobacco from the crew. They had promptly taken to the bush at the first distant view of the strange, enormous mechanical bird.
Bolting the hatch over the for'ard motor-room and at the same time telling the craven Rioguayan that there was nothing to be afraid of, provided he behaved himself, Peter and Brian Strong removed one of the fifty-pound bombs from the dropping gear and carried it ashore. Then, armed with rifles, they transported their bulky load to the enormous rust-red pipe-line that was raised eight feet above the ground, stretching miles in either direction, upon which depended themain kerosene supply to the Rioguayan arsenals and aerodromes.
It was the work of a few minutes to place the bomb close to the pipe and "tamp" it with earth. In the absence of a time fuse, it was necessary to detonate the explosive by rifle-fire.
At a safe distance, Peter put bullet after bullet at the target. The pipe was holed in several places, the oil gushing forth at high pressure, but it was not until the tenth shot that the desired result was attained.
There was a deafening crash. To quote Brian Strong's words: "It was as if the entire contents of an ironmonger's store had been dropped from the top of a skyscraper". A cloud of dust and smoke rose high in the air, mingled with fragments of jagged iron. Flames fifty feet in height shot up from the pipe, spreading far and wide as the inexhaustible supply of highly inflammable oil poured out in torrents to add to the work of destruction.
"That's kippered the show," remarked Peter gleefully, as the two Englishmen retraced their steps to the flying-boat.
The next business was to "pay off" the Rioguayan engineer. He was given a supply of provisions and a liberal quantity of tobacco and told to clear out and not to hurry back to San Antonio; while, for self-protection, he was provided with a rifle and twenty rounds of ammunition.
"You might have made him start up the motors,Peter," remarked his uncle, as the mechanic disappeared in the undergrowth.
"Thought I'd try my hand at the job," replied his nephew.
The for'ard pair of motors fired without hesitation, but the after ones gave a certain amount of trouble. At length, with the four engines throbbing and out of gear, Peter made his way to the pilot's seat.
At a steep angle, the flying-boat rose skywards. As she did so, a rifle bullet "pinged" harmlessly against the light steel armour plating of the fuselage.
"Ungrateful brute, that mechanic," was Peter's only remark.
Ten minutes later the fiercely burning oil pipe was a mere speck in the distance. The flying-boat, at an altitude of three thousand metres, was heading for the distant Sierras, that rose in a far-flung barrier of irregular projection to a height averaging nine thousand feet above the sea-level.
The aircraft was flying "all out", her speed, on account of the rarefaction of the atmosphere, being a little less than 140 miles an hour.
Peter was in a hurry. It was most desirable that the mountains should be crossed well before dark. Apart from the risk of crashing blindly against one of the many almost vertical peaks, there were the dangerous air-pockets and eddies to be taken into consideration, and with the setting of the sun, and the consequent rapid cooling of the earth's surface, the higher altitudeswere certain to be disturbed by raging winds that attain the velocity of a hurricane.
For miles the ground rose steadily. Viewed from a height, the rise appeared to be gradual, since the smaller irregularities were apparently flattened out. It was only by judging by the shadows cast by the sun, which was now well down in the west, that the numerous valleys and ridges could be noticed.
For the first hundred miles, the country was well wooded. Then came a wide belt of grass land, gradually merging into an arid waste absolutely destitute of vegetation. The desert marked the beginning of the Sierras, which were now plainly visible at a distance of thirty or forty miles.
"Think she'll do it before dark?" inquired Uncle Brian, glancing at the sun, now only about thirty degrees above the horizon.
"Rather," replied Peter. "It will be quite light up here after the low-lying ground is in darkness. Once we're above the peaks I don't mind. It will be plain sailing after that."
"If you're sure of it, well and good," rejoined Brian. "If not, we'd better make a landing while it is light." The youthful pilot shook his head.
"Twelve hours saved is twelve hours gained," he said sagely. "I don't want to spend another night in Rioguayan territory if it can be avoided. She'll do it."
Fifteen minutes later, a violent bump announced that the flying-boat had struck an air-pocket, a clear indication of the adverse conditions that awaited herabove the snowy peaks of the Sierras. She dropped vertically for nearly a thousand feet in spite of the pilot's efforts to counteract the sudden loss of "lift". Then staggering blindly into the furthermost wall of the invisible air chasm, the flying-boat "stalled" and almost stood on her tail, until she picked up and Peter was able to bring her back to her normal trim.
The next five minutes was a perfect nightmare. Above the snowy crags, now pink in the diffused rays of the setting sun, she sped, side-slipping, banking, and plunging, as if scorning the desperate efforts of the pilot to keep her up.
Once she nose-dived, flattened out, and made straight for a sheer wall of rock that a few seconds previously she ought to have cleared with a thousand feet to spare. Vainly Peter put the vertical rudders hard over. It seemed as if a collision was inevitable and that the shattered debris of the flying-boat would fall headlong into the fathomless chasm, when a side gust of terrific force hurled her, like a leaf, crab-fashion, so that she just scraped clear with a few feet between her port wing-tips and the pitiless face of the peak.
Then, propelled upwards by a freak air-current of irresistible strength, the flying-boat was hurled, like a sheet of paper up a tall chimney, between the perpendicular walls of a deep defile. So near did she scrape the summit of one of the twin peaks, that the rush of air dislodged a mass of snow, sending it thundering into the abyss, with a roar plainly audible within the supposedly sound-proof pilot's cabin.
Suddenly the roseate snow peaks gave place to a void of intense darkness. The crossing of the Sierras was accomplished. Ahead lay miles of country, sloping towards the Caribbean Sea, with nothing higher than three thousand feet to be encountered—at least, so the map read.
"We're over!" exclaimed Peter thankfully, as the flying-boat settled down to her normal even style of flight.
"More by luck than by anything else," thought Uncle Brian, who felt bruised and shaken all over.
"I'll take her down to eight thousand feet," continued Peter briskly. "Then I'll get you to stand by, Uncle. There's nothing to be done except to watch the altimeter and the compass. There's no need to bust along now. We've ten hours of darkness in front of us and we don't want to find ourselves miles out over the Atlantic when day breaks. I'll cut out the after motors."
In spite of the fact that the interior of the fuselage was heated by pipes connected with the exhausts, the air within the cabins was bitterly cold, and the temperature fell yet lower after the rear pair of motors was shut down.
Peter was now feeling very sleepy. Lack of proper rest, the excitement of the last two days, and the effect of the rarefied atmosphere all combined to reduce him to a state of resistless drowsiness.
"You turn in," said his uncle peremptorily. "I'm good for another ten hours, if needs must. If there'sanything requiring your attention, I'll wake you."
The elder man "took on". Since the flying-boat was built largely after his designs, he was well acquainted with the technical part of the mechanism and construction, but he was quite a novice in the art of actual flight. As long as things went right, there was little for him to do.
Peter, wrapped in half a dozen blankets in addition to a leather flying-coat, was soon sound asleep in spite of the low temperature.
He had not slept for more than ten minutes when his uncle roused him.
"She's faltering—both engines," announced Uncle Brian laconically.
Peter rose stiffly to his feet. He had not the trained ear for mechanism that his uncle possessed, and as far as he could hear, the motors were still keeping up their rhythmic purr.
"Look at the gauge of the main fuel tank," suggested Uncle Brian.
His nephew picked up an electric torch and made his way to the 'midship compartment. He went sceptically enough, but on consulting the indicator, the state of the gauge fairly startled him. It stood at zero.
That meant that only one of the auxiliary tanks contained any kerosene, and owing to its position was useless unless the flying-boat was diving steeply or in an inverted position while "looping".
The tanks were three-quarters full when the flying-boat had passed out of Rioguayan control; and sinceonly a few hours had elapsed, it was a matter of impossibility for the four motors even running all out to "mop up" anything like the quantity that had gone somewhere.
A hasty examination revealed the cause of the leakage. A drain-cock was half open, allowing a steady stream of kerosene to flow into space. At first thoughts, Peter attributed the leakage to the Rioguayan mechanic, until he remembered that the fellow had been locked up when left alone on board.
But there was little time for speculation.
Hastening back to the control compartment, Peter found that the for'ard motors were now firing spasmodically. In a few moments they would cease functioning for lack of fuel, and then there was nothing to keep the flying-boat from descending with fair rapidity. Her weight and relatively small plane-area were against her for prolonged gliding.
He touched his uncle on the shoulder and motioned him away from the controls.
"Luck's out this time," he said grimly. "It's a thundering big drop in the dark."
Peter had barely resumed charge, when the motors coughed and stopped. A deadly silence succeeded the purr of the engines, since the rush of air past the metal planes was inaudible within the sound-proof compartment.
It was the pilot's chief concern to keep the flying-boat up as long as possible. It was entirely beyond reason to suppose that the gliding would be prolonged till dawn, but the longer the aircraft kept up the better, since there would be more time to make preparations for the forced landing.
Planing as nearly in a horizontal direction as possible for two minutes, was followed by a short steep rise until the flying-boat seemed in danger of "stalling". This manoeuvre Peter repeated, knowing that for every hundred feet of vertical drop he could knock off twenty or more by the sudden leap against gravity.
For quite twenty minutes he held on, his hand dexterously manipulating the controls, while his eyes never left the altimeter and speed-indicator.
Meanwhile, Brian Strong was busy. Realizing thatperhaps the flying-boat might be able to land on fairly even ground, he set about to prepare the electric head-lamp which could be trained in a vertical arc of fifteen degrees—enough to illuminate a sufficient length of ground before the machine came in contact withterra firma.
The searchlight was of the accumulator type. According to instructions issued to the Rioguayan airmen the batteries were to be kept fully charged; but when Brian tested the circuits he found that the accumulators had completely run down.
There remained the secondary head-lamp—a three-hundred candle-power acetylene-generated light.
Hoping against hope that this apparatus was in working order, Brian unfastened the lid of the generator. The acetylene chamber was full of perfectly dry carbide, but the water compartment was empty.
"How long can you give me?" asked Uncle Brian.
"Five minutes—ten, with luck," was the reply.
Hurrying to the water-tank, Brian turned the tap. There was no flow.
"Has every tank in this confounded contraption run dry?" demanded Brian. Then the solution of the mystery dawned upon him. The water in the tank was frozen into a solid block.
Had the motors been water-cooled a way out of the difficulty would have been simple; but being air-cooled no help was forthcoming from them.
Seizing a spanner, Uncle Brian vigorously attacked the six nuts securing the circular plate on the top ofthe water-tank. The cover removed, he hacked at the ice until he was able to gather a double handful of chips of frozen water. These he placed in a can and held them over the still warm cylinders of one of the motors until the vessel contained about a pint of fluid.
"Look sharp!" shouted Peter. "We can't be much more than a thousand feet up."
Working feverishly, Brian poured the water into the generator, turned on the needle-valve to its fullest extent, and applied a match to the triple fish-tail burners. With a mild explosion the gas ignited, and the powerful beam flashed out into the night.
"Good heavens!" exclaimed Peter, aghast, for the bright white light was playing on a solid substance less than four hundred yards away—the steeply rising face of a formidable mountain peak. Only a few seconds separated the flying-boat from an end-on crash.
Putting the vertical rudders hard over, Peter literally jerked the machine round, tilting her to an angle of nearly sixty degrees as he did so.
Unprepared, Uncle Brian lost his balance and fell violently against the lee-side of the compartment. Before he could regain his feet, the flying-boat pancaked and crashed.
Peter had a brief vision of the nose crumpling up and the under-carriage being forced through the steel floor of the fuselage. Then the long slender body rose until the tail was almost vertical. The pilot, hurled against the instrument-board, lost all interest in the immediately subsequent proceedings.
Brian Strong came off fairly lightly.
Owing to the circumstance that he was lying inertly upon the floor—for after his first attempt to rise he had philosophically abandoned further effort—he had escaped being flung headlong against the bulkhead. As it was, he found himself lying on the ground with wreckage on either side of him—while within two yards of his feet were the remains of the acetylene head-light, with a flare of vivid white light leaping twenty feet into the air.
"Never did think much of those acetylene lamps," he remarked to himself, and tried to puzzle out by what means he found himself where he was.
It was indeed fortunate that the fuel supply of the flying-boat—there were about twenty gallons in the lowermost tank—was non-inflammable when released from pressure; had it been ordinary petrol the wreckage would have been a mass of molten metal and the two airmen would have been burnt to ashes.
Still muttering incoherently, Uncle Brian sat up and rubbed his head vigorously.
"Where am I?" he demanded.
He dug his hands into the ground. It was fine sand. He sniffed at it, half expecting to find it salt like the sand of the seashore.
Still puzzled, he watched the strongly-burning acetylene until the glare was too much for his eyes. He turned his head, but was unable to discern a single object.
Then he crawled, like a stricken animal, away fromthe light, until a mass of twisted steel plating impeded his progress.
"There's been a most unholy smash," he declared solemnly.
Gradually coherent reasoning returned to him. Strangely enough he completely forgot that Peter had been with him in the crash. His chief thoughts were for the safety of the essential parts of the secret-ray apparatus. Those placed in a locker in the flying-boat were probably smashed, but there remained the most important object of all—the delicate valve which he had hidden in an empty cartridge case.
Almost feverishly he tore open his leather greatcoat and felt for the cartridge-belt that had been his constant companion from the time he left El Toro. With trembling fingers he extracted the small glass phial and held it up to the light. Then he gave a gulp of relief and satisfaction. The delicate filament and the minute and complex mechanism were intact.
"Hello, Uncle! Taking a blood test?"
Brian Strong turned at the sound of the well-known voice. Walking unsteadily towards him was Peter Corbold.
His nephew was still wearing his flying-coat and helmet, which he had put on merely for the sake of warmth. The coat was rent in half a dozen places, while the left side of his face was red with blood welling from a cut on the forehead.
Peter's period of insensibility had been of short duration, Thrown clear of the wreckage after hisimpact with the instrument-board, he had got off with a nasty bruise on the forehead. The padded helmet had saved his skull from being fractured, but the blow had been sufficient to cause the blood to flow freely. His head was whirling, he felt horribly sick and as weak as a kitten, yet he could not repress a facetious remark upon seeing his relative so absorbed in his precious invention.
"We're here," continued Peter. "But where, goodness only knows. What's your damage, Uncle Brian? Wasn't it a jolly old crash? It reminds me of a song we used to yell in the gun-room of the oldBaffin: 'She bumped as she'd never bumped before.'"
"And never will again," added Uncle Brian with emphasis. "What's to be done now?"
"Sleep till the morning," replied the practical Peter. "My head's buzzing like a top. There's a chunk of the old 'bus that will make quite a decent bunk. I vote we turn in."
Eight hours later Peter awoke to find the sun shining brightly. His headache had vanished and—good sign—he felt ravenously and healthily hungry.
Uncle Brian was still sleeping soundly. Peter let him sleep. It would give him an opportunity to take stock of the locality.
Throwing off his blankets and greatcoat, for the heat of the sun was oppressive, Peter emerged from his retreat and stood blinking in amazement in the dazzling light—sheer amazement at their marvellous escape.
The wrecked flying-boat was practically in the centreof a circular patch of sand and gravel about three-quarters of a mile in diameter. On all sides rose rugged mountains with precipitous faces in places rising sheer to a height of at least two thousand feet.
The plain was almost dead level and absolutely destitute of verdure. No sign of life was visible. The flying-boat had struck a snag in the form of a mass of rock about four feet in height and less than a couple of yards in circumference. Otherwise, the sandy waste was free from irregularities. It would have been an ideal landing-ground, for the sand was fairly hard; and it was certainly a case of sheer hard luck that the machine should have wrecked herself on the only dangerous bit of ground in the extensive circle.
On the other hand, it was a rare slice of good fortune that had accompanied the flying-boat on her downward glide. She must have skimmed the summit of the encircling mountains with but a few feet to spare. In the darkness Peter had been in entire ignorance of the danger. Equally fortunate was the fact that the timely lighting of the acetylene head-lamp had enabled the pilot to escape crashing nose-on against the opposite wall of the huge basin of natural stone.
"We're here," decided Peter grimly. "We're here; but goodness only knows how we are going to get out. It's been a fine old smash-up. However, there's some consolation: the Rioguayan air fleet has lost one unit."
So severe had been the impact that both of the for'ard motors had broken away and lay quite fifteenyards from the crumpled bows. The after portion of the fuselage had broken off short, forming with the buckled 'midship part an irregular, inverted "V". Four of thesubsidiaryfuel tanks had completely parted company with the hull, while the steel water-tank had burst from its securing bonds and now rested bottom upwards upon the sand. The tank was practically intact, but, since Uncle Brian had not had time to replace the cover after chipping the ice, the precious contents had drained into the parched ground. The outstanding feature was the sight of the two rear propellers, both intact, standing up like flaming crosses as the sunlight glinted upon the polished metal blades.
"And we're a long way from the sea," exclaimed Peter aloud.
"Did I hear anyone say 'tea'?" inquired Uncle Brian, from the depths of his temporary sleeping compartment. "If so, many thanks."
"You didn't," replied his nephew. "There's nothing doin' in that line, I'm afraid. No water to be had."
"That's a rotten look-out," said Uncle Brian, as he emerged from his retreat. With his bruised features, torn clothing, and staggering gait, he looked more like a dissipated tramp than an engineering expert.
He glanced at the debris, then at the mountain barrier.
"The old horse jibbed at that fence, Peter," he added. "It'll mean padding the hoof for us, I fancy. Any grub going?"
Scrambling over a litter of steel sheets, Peter dived into the debris that remained of the 'midship part of the flying-boat. After hunting about for some time, he discovered the oddly assorted contents of the provision-room. He managed to rescue a couple of tins of pressed beef, a loaf made of maize, and a bottle of soda water—the sole survivor of nearly four dozen.
"Enough here for the present," he announced, as he crawled out. "We shan't starve if we can carry enough away with us."
The frugal meal was eaten in silence. Uncle Brian produced a spirit flask, half filled with brandy. Pouring about a couple of tablespoonfuls of soda water into the metal cup, he handed it to his companion.
"Your liquid ration, Peter," he said solemnly. "We'll have to make it last out till we find water."
No time was lost in making preparations for the long trek. Each man had to carry as much as he possibly could without impeding his movements. Uncle Brian took the remaining parts of the secret-ray apparatus, which he discovered lying in the sand undamaged and still in the haversack. The rest of his load consisted of a rifle and ammunition, a blanket and waterproof sheet, and about ten pounds of foodstuffs. Peter loaded himself up with his sleeping-bag, twenty pounds of provisions, the liquid compass from the flying-boat, a coil of light line, his automatic, matches, and—in anticipation of finding water—an empty water-bottle with slings attached.
"We shan't have to do very much climbing to get out of this," declared Uncle Brian. "And I shall be very disappointed if we don't find water within an hour or two. At one time this place was a mountain lake. The water has drained away—where? Not through the sand, because it's a certainty that the bed of the lake was hard rock similar to the surrounding mountains. It flowed away through a canyon. If we find the canyon we find our way of escape."
Peter agreed, but up to the present there was not the slightest visible sign of a gorge. The enclosing wall of rock seemed continuous, without a rift lower than five hundred feet above the plain.
Progress was slow. The sand, although tolerably firm, was hard going. The heat of the sun, coupled with the weight of their burdens, distressed both men severely.
Presently they came to a shallow depression resembling a North American gulch or a South African drift, only bone-dry. At one time it had been a watercourse. The bed was littered with small stones.
Uncle Brian stooped, picked up one of the rough pebbles, and examined it.
"Would you like to be rich beyond the dreams of avarice, Peter?" he asked. "If so, load up. These are rough diamonds."
His nephew looked incredulous. He half suspected that the sun, following the concussion of the crash, had affected his uncle's brain.
"Fact," continued Brian Strong. "The quantity of diamonds here would make the De Beer's reserve look silly in comparison. We'll take a few—just a few—to support our statement, should we be lucky enough to come through. Personally, I'd rather have a pint of pure water at the present time.... Enough, Peter! Don't sacrifice mobility to cupidity. Later on, perhaps."
In his present state of mind, Peter, once he wasconvinced of the sincerity of his uncle's announcement, was not greatly impressed by the magnitude of the discovery. The mere fact that untold wealth lay at his feet was as nothing compared with his anxiety to get clear of the mountain-enclosed arena. He hardly doubted his ability to find a way out; but it was the long and tedious tramp that rather appalled him. The change from speedy flying to a trudge afoot at two and a half miles an hour, when time was of the utmost importance, was a disconcerting prospect.
"There's an outlet," declared Uncle Brian, pointing to a bluff that even at a short distance merged into the sombre greyness of the mountainous wall. "We'll find a gorge close to it."
"Let's hope so," added Peter.
"There must be some egress," continued Uncle Brian. "At some time—centuries ago—when this place was a lake—the overflow escaped in a northerly direction. Why? Because to the south'ard are the Sierras, which form a watershed between Rioguay and Venezuelan territory. For some reason—an earthquake, most likely—the feeders dried up or were diverted. Consequently, the lake ran dry. Yes, here we are."
The cleft was so narrow that there was barely room for the two men to walk abreast. The walls, up to a height of thirty feet, were quite smooth, bearing evidence of the friction of sand and water for countless ages. Above that height they were rugged andirregular, so that in many places the sky was completely shut out from view.
For nearly a hundred yards they progressed with tolerable ease. Then the gorge contracted to such an extent that Peter's broad shoulders were rubbing against either wall. Once or twice he had to turn sideways and drag his pack after him.
"Hope it isn't going to be a blind alley!" he exclaimed.
"Never fear," declared Uncle Brian encouragingly. "The floor is on the down-grade all the time. That's a sure indication that——"
"We're done this trip!" interrupted his nephew. "There's been a fall of rock."
In the subdued light the defile appeared to terminate abruptly in a barrier of enormous stones, some of which must have weighed at least a thousand tons, rising to quite seventy feet.
"Fallen recently," commented Peter. "By Jove! If there's another smash-up, we'll either be flattened out, or trapped. Let's go back!"
Uncle Brian deliberately unburdened himself of his load.
"Let me get past you," he said. "Before we talk of going back, I'll make a brief examination. H'm, yes! Recent fall, eh? You're wrong, Peter. That mass of rock probably subsided a thousand years ago. The dryness of the atmosphere accounts for the fresh-looking stone."
"Possibly," rejoined Peter, "but that isn't of muchconsequence to us, is it? It doesn't make our job any easier. I might be able to scramble up and lower the rope for you."
"No climbing for me, thank you," replied his uncle. "I'm going to crawl under."
He pointed to a small cavity, barely two feet in height and triangular in section, between two masses of stone inclined one to the other.
"You can't possibly," began Peter.
"Can't I?" retorted his uncle. "Wait till we shift some of the sand. It may be ten feet deep, but it has accumulated since this rock fell. The stone is quite smooth.... Just come here a minute and kneel down. I fancied I saw daylight; do you?"
Peter looked through the narrow tunnel. Sure enough, at about fifty feet away, he could discern the farther end of the horizontal shaft.
"No need to dig," he declared. "Stand by. I'll crawl through and pay out the rope."
It was a nerve-racking experience. Notwithstanding Uncle Brian's assurance as to the well-established nature of the barrier, Peter was haunted by the dread that the wall of the tunnel might subside; and when about half-way through, he had grave doubts whether he could wriggle past a particularly narrow section. At any rate, there he was. He could not turn to crawl back. He simply had to go on, or get stuck.
With his heart figuratively in his mouth, the perspiration pouring down his face, his hands and knees raw with the friction of the sand, Peter continued hisway, turning on his side in order to negotiate a couple of narrow places where the rocks protruded.
"Worse than the double bottoms of a battleship, any old time," he soliloquized. "Now, if I butt into a particularly venomous snake at the far end—that will be the limit!"
At length Peter emerged from the tunnel, rose to his feet, and drew in a copious draught of fresh air.
"Through!" he shouted.
"Right-o!" sang out his uncle. "Steady on while I finish with the gear.... Now then, haul away!"
Peter began to haul in the line. It was heavy work, for at the other end was attached the baggage belonging to both men, Brian Strong's haversack with its precious contents being secured for safety within the folds of the blankets and sleeping-bag.
"Good thing the rope's new," thought Peter, carefully coiling away the line as he hauled it in. "If it did part half-way through there'd be a fine old lash-up!"
Presently an increased tension of the rope announced that the load was passing the narrowest part of the tunnel, which was about fifteen feet from the end. Then there was a sudden jam. Something had fouled, and the whole of the gear was wedged tightly, forming a formidable barrier between Peter and his relative.
In vain the former heaved and hauled. He could hear Uncle Brian plaintively inquiring when he would be able to crawl through.
"There's no help for it," decided Peter. "I'll have to go in again and clear the lash-up."
He did not relish the task, but it had to be done. The journey through had been bad enough, but now, although the distance was much shorter, he was additionally hampered by the fact that he was working in utter darkness and that the baggage, filling the height and breadth of the tunnel, considerably interfered with the air supply.
Peter realized the possibility of having to cast off the rope and remove each bundle separately—a task entailing at least half a dozen trips into the shaft.
Fortunately this was spared him; for on feeling cautiously, he discovered the cause of the "block". The rifle had come unhitched and, swinging round until the muzzle caught the projecting rock, had jammed the whole contraption. It was a fairly simple matter to release the rifle and drag it into the open. Then the rest of the gear was hauled out with comparative ease.
"All clear," shouted Peter again.
Brian Strong made the passage quickly and easily. As a mining engineer, he was used to crawling through narrow passages. Had it been a case of making their way aloft to the fire-control platform of a battleship in a heavy sea-way, Peter would have won easily; but as a tunnel crawler, he admitted unhesitatingly that he did not shine.
For the next mile, it was fairly easy going. The floor of the ravine was wider, but the height of the walls correspondingly higher. Here and there were pieces of rock that had become dislodged and had fallen, halfburied in the sand. Once a stone as big as a man's head came hurtling down within twenty paces of them.
The end of the chasm was now in sight, but they were not yet out of danger or difficulty. At about four hundred yards from the end their progress was arrested by a single slab of rock about ten feet in height that completely obstructed the passage.
This time there was no tunnel. The only way was to climb over.
"I'll give you a leg up, Uncle," suggested Peter. "Then I'll send up the gear and swarm up by the rope."
He took up his stand close to the rock and was about to bend down to enable Uncle Brian to clamber on his back, when his boot came in contact with something hard, buried a few inches under the sand. As he trod on it, it gave with a rasping sound.
"Hello!" he exclaimed. "What's this?"
With the toe of his boot, he pushed aside the covering layer of sand, revealing a rusty breast-plate. Grasping the metal, he pulled it up. It came quite easily, disclosing a number of human bones lying on the backpiece of a suit of mail. A short distance away was a steel morion, together with fragments of a skull.
The discovery roused Peter's interest far more than had the sight of the diamond-studded sand.
"We're not the first people to find the gorge," he remarked. "How old is this, do you think, Uncle?"
"Seventeenth century or late sixteenth," replied Brian Strong. "The lace-holes in the breast-plateprove that. A Spaniard, I should imagine. He was crushed by the rock. I don't suppose he was alone. We may have walked over the bodies of his comrades buried underneath the sand."
"It would be interesting to know——" began Peter, then he broke off suddenly, adding, "Come on, let's get clear of this rotten hole as fast as we can."
Half an hour later, they emerged from the canyon. Ahead stretched a seemingly endless expanse of trackless forest; behind them, the mountains.
"There's bound to be water down there," said Brian. "And if there's water, there's a stream. The stream becomes a river, and the river flows into the sea—in our case, the Caribbean. We'll have to skirt the fringe of the forest until we strike a stream."
This reasoning proved to be sound. It was not long before they came across a small rivulet gushing from the hillside.
This they followed, noting with satisfaction that it grew steadily in volume. For four days they kept to one of its banks, sometimes cutting a way through dense undergrowth, at others wading in the clear shallow stream. Wild animals they neither heard nor saw. Several times they had narrow escapes from poisonous reptiles. At night they were tormented by mosquitoes; by day they were almost knocked out by the moist, enervating heat. Their clothing was in rags, their boots cut almost to ribbons.
Yet they held doggedly on their way, living on short rations and sustained by the hope that every stepbrought them nearer to the sea, though there were no signs of approaching the outskirts of the forest.
On the fifth day, both men felt utterly done up. Too exhausted even to speak, they plodded on, until their progress was arrested by the stream flowing into a wide river, literally alive with caymans.
"Voices!" exclaimed Peter.
Both men listened intently.
Brian Strong shook his head.
"Imagination!" he replied briefly.
"'Fraid you're right," rejoined his companion disconsolately, but seized with an inspiration, he drew his automatic and fired two shots into the air.
A few minutes later, a dug-out canoe, manned by a dozen Indians, appeared round the bend of the river.