And as the rough voices swelled upwards, a weird answering chorus floated back to them from the summit of the mountain, and lo! several dark forms appeared outlined against the starry sky. Emu Bill ceased his vocal exercises at once, and squirmed about uneasily until the flute stopped.

"Say, mates," said he, anxiously; "I hope it ain't no corroborree song they is singin'."

Mackay glanced upwards, then hastily grasped his rifle, but the vague voices in the air broke afresh upon his ears just as he was about to pull the trigger, and he laid the deadly weapon down with a shudder.

"They are actually mimicking that bonnie hymn," he said nervously. "I—I haven't the heart to shoot——"

"And aren't their voices almost musical!" cried Jack, whose ear was keenly attuned to melody. "They make a very much better attempt than our corroborree savages did about a week ago; their voices were simply hideous."

"The aborigines are born mimics, Jack," answered Mackay; "but, as you say, their song is usually enough to drive a man to drink—providin' he can get it. Still there may be a different sort o' savage in this mysterious country. If the land itself is better, it would influence the people, and who knows maybe they have acquired some accomplishments unknown to their brethren on the flats."

"I can't make them out at all," said Bob, quietly. "Everything seems so unreal, so—so uncanny about here, and these niggers singing that hymn have given me the creeps."

"Let me have one go at 'The Muskittie's Lament,'" pleaded the Shadow. "I reckon it would bust them up to mimic that high note——"

"You leave that long-suffering muskittie alone," said Mackay. "We'll bust them up wi' something more solid in the morning. I'll climb that mountain or go under trying."

Conversation somewhat flagged after that. The events of the day had all been so strange and inexplicable; the lure of the mountain was becoming oppressively potent, and each of the staunch little band was filled with his own secret convictions regarding what might lie beyond.

"Better turn into your blankets, boys," said Mackay, at length. "You'll need all your energies in the morning. I'm going to keep watch and see that nothing happens while you sleep. I'm not going to risk another wipe out in this quarter."

"You ain't goin' to do sentry go on your own," spoke Never Never Dave. "I reckon I'll take my turn."

"An' me, of course!" cried Emu Bill.

"And ain't the poor, low-down Shadow any good?" complained that individual, pathetically. "Let me do a prance round, boss. I ain't a bit sleepy."

"Let Jack and me take it for the first night," said Bob, quietly.

Mackay laughed. "I know you are all vera willing, my lads, but the first night is my care; I'll ask Bob, who is next in responsibility, to take part o' the watch. Jack and the Shadow will be on duty to-morrow night, and you, Bill and Never Never, can take the next;" which equable arrangement appeared to suit every one.

Then Bob arose, rifle in hand, and stepped forward.

"No, no, Bob; not yet," said Mackay. "I'll call you in three or four hours to take a spell. Lie down and sleep for a bit, my lad."

But Bob was obdurate. "You've been wearing yourself out these last few days," he said simply. "You can surely trust me to fill your place for the first half of the night, at least. Perhaps I may not need to call you, for I know I couldn't sleep if I tried. My brain is buzzing with odd ideas, which would be bound to keep me awake."

The elder man hesitated for a moment, then gave in. "But promise to call me at one o'clock, Bob," he said, "otherwise I'll stay up with you;" and Bob promised.

A few minutes and a row of sleeping figures lay outstretched around the fire. Bob tightened up his cartridge-belt, pulled up the heads of several cartridges so that they might be easily extracted in an emergency, examined the magazine of his gun, and closed the breech gently, bringing the trigger to full cock. Then he waited, motionless as a statue, beside the huddled forms of his comrades, with rifle upraised, and every nerve strung at highest tension. Well he knew that danger threatened; he felt it in the air; an ominous calm prevailed; how soon would it be broken by the savage yells of the guardians of the mountain? Bob gripped his rifle the tighter, and his eyes scanned the near distance critically, then roamed aloft to the now deserted mountain summit. A slight sound startled him, and his finger closed gently on the trigger of his weapon, but it was only Mackay tossing restlessly in his blanket. Bob looked pityingly at the sleepless form, and at that moment Mackay beckoned him.

"I canna get it out o' my mind," he whispered, "that when I followed the tracks o' the blacks, they led right into the mountain an' no' round about it, an' it beats me to know how they managed to climb over so quickly. Keep a careful watch, Bob; keep a careful watch."

Bob nodded silently and returned to his position. He had unconsciously shared Mackay's fears before they had been spoken. Since he first saw the mysterious mount he had marvelled how it had been scaled, and how descents had been accomplished.

The Southern Cross slowly sank to rest, and the edge of the Great Bear constellation peeped above the northern horizon. Yet still the watcher stood erect at his post, and the camp slumbered.

CHAPTER XIV The Struggle by the Mountain

It was well after midnight, and Bob still stood guard over the sleeping camp with undiminished vigilance. Not a sound in the air escaped him; he heard the distant scream of the curlew with a shiver of dread, then nearer at hand the dull monotone of a mopoke resting on some rocky ledge overhead would reach his ears as a dismal calling from a shadowy world. Again would come a period of silence, broken only by the gurgling echoes from the sulphur springs, and the regular breathing of the sleepers. Bob pulled himself together impatiently, he had felt himself relaxing into a kind of stupor wherein all things grim and melancholy appeared to him.

"I wouldn't have believed," he muttered, "what a shattering influence a night watch has on a man's nerves."

The long wailing cry of a dingo now penetrated piercingly over the desert from the west, and the watcher stirred uneasily at the mournful sound which seemed to convey in it all the sadness and despair of a voice from the nether world.

The weird notes had scarcely died away when he became conscious of a peculiar tap-tapping almost close beside him. He could not make it out; the black surface of the barring range rose before his eyes, but he could distinguish nothing there, and the moon shone clearly on the giant rock. Tap! Tap! Tap! Softly the echoes came but imperceptibly growing louder; anxiously he scanned the bare hillside for some clue to the mystery, and as his eyes reached the ridge of the mountain he was startled to see a tall beshrouded figure standing there, and apparently gazing down upon him. Bob was certain the apparition had not been in the same place but a minute ago, and surely he could not be responsible for these strange noises which seemed to come from the mountain, yet with no cause showing. Tap! Tap! Tap! Harsher and more metallic the ghostly reverberations rang, and now a faint call wafted down from the heights; again and again it came, gently falling on the mystified listener's ears like a voice from the skies, and the strange figure aloft waved his arms in wild gesticulation. Sharper and still sharper sounded the demoralizing tapping, and with it now came a curious shuffling, slight almost to noiselessness, but Bob's sensitive ears were not to be deceived. A cold sweat broke out upon his brow; the vague disturbances of the night were issuing not from the side of the mountain, but from its interior! With a quick stride he reached Mackay, and at a touch the sleeper awoke.

"What is it, lad, what is it?" he asked, breathlessly, his rifle already in his hand.

Bob placed his finger on his lips, and pointed silently to the mountain.

"They're coming through it!" he whispered, hoarsely.

Mackay nodded briefly, and strode silently over to the resounding wall, and Bob hastily aroused the sleepers. In a moment the camp was prepared, and meanwhile Mackay was walking stealthily along the base of the mount, his ears bent down to the rock as he strove to locate the mysterious alarms. And now the distant call from the hilltop floated down to them once more, and Emu Bill started at the sound, and looked up wonderingly, for the faint double note of a coo-ee had this time been plainly heard, and the tall form on the distant heights was despairingly pointing outwards across the desert.

"That nigger can coo-ee like a good 'un," muttered he, "an' he's tryin' to warn us. I reckon that's because we didn't shoot him to-day; but I never believed a nig could feel any gratitood."

Suddenly the echoes ceased, and all was silent as a tomb. Bob looked, and saw Mackay crouched hard against the rocky wall on the edge of a deep fissure which showed down half the face of the mountain. He seemed like an animal preparing for a deadly spring.

"I reckon we should go over beside him," said Never Never Dave, but so speedy had been the developments of events that there was no time to decide upon a definite course of action. Indeed, not one of the party guessed what wild happening was about to take place. Bob somehow expected to hear the preliminary yells of an attacking horde, even as they had heard them before, but no such outcry took place. He saw Mackay beckon wildly with one hand over his shoulder, and quickly he obeyed the summons, the others following with silent footsteps. Then a stone clattered noisily at the bottom of the ravine, and to Bob's amazement, a swarthy face appeared from the depths, surmounted by a tall waving head-dress of feathers. As the warrior emerged further into view, Bob's astonishment increased, for here was no naked savage, but a gorgeously arrayed aboriginal, splendidly proportioned, and carrying in his hand a long curved bow and several arrows. Bob had just time to note this much and no more, for Mackay's rifle belched out almost in the new arrival's face, but the shot had been fired with the hands resting loosely on the ground, and the bullet sped high, scattering the nodding plumes of the astonished black in all directions. With a cry of pent-up fury, Mackay lunged forward to grasp his prey, and at once the stalwart native closed with him. And now crowding up behind, one by one, a solemn procession of similarly attired warriors came trooping. The first of the number without hesitation rushed to the assistance of his struggling comrade, the others calmly bore down upon the little group, who, with Bob at their head, had watched the scene as in a dream. With a hoarse snarl of rage Never Never Dave opened fire, and almost at the same instant the entire artillery of the camp spouted out flame and smoke and leaden hail. In reply, a cloud of arrows flew about their heads, and Bob felt one pierce the muscle of his arm, but he pulled out the slender barb with a wrench, and again his rifle spoke, and the roar of many reports in his ears told him that his comrades too were strenuously engaged. Backwards and forwards the spectral warriors surged, and yet never a sound escaped their lips, and they strove with steady effort to come to close quarters with the camp defenders.

Meanwhile, Mackay was engaged in desperate encounter on the edge of the fray. His first antagonist he had flung from him almost immediately, limp and broken, from that dreadful clutch. The second he had rendered hors de combat with a single blow of his mighty fist. Then two more rushed upon him, but profiting by the experience of their brethren they evaded his circling arms, and hurled themselves upon his lower limbs, and there they clutched leech-like, while others hastened to attack him from behind. Mackay marvelled for the moment why they had not shot him down with their arrows; his own rifle had been thrown aside after the first fruitless shot, but now his revolver flashed in his hand, and the weighty stock came down crash on the head of his nearest encumbrance, but before he could use it again, he was seized from the back and pulled to the earth, yet even as he fell his revolver exploded upwards into the faces of his foes, and he chuckled in grim joy as he felt their relaxing hold. It was at this stage that Bob missed him from their midst. The attack had drawn off somewhat, and he glanced around for the first time in search of his companions. Then he noticed the seething band standing over the fallen giant, and a wild fury filled his heart.

"Come on, boys," he cried, "Mackay's down!" and he dashed to the rescue.

Quick as he was Never Never Dave was quicker, and his clubbed rifle swung light as a feather in his strong right hand, but it fell heavy as lead on the heads of the all too previous natives, who had not looked for further molestation from that quarter. With a guttural exclamation they leaped aside, and Mackay arose bleeding and scarred. But the end was not yet; even while the defenders were congratulating themselves on their victory the natives once more swooped down upon them, and their arrows whistled loudly through the air. They had guessed that the death-dealing weapons of the little party had lost their power, for indeed there had not been a shot fired these many minutes, and the magazines of the rifles were empty. But they still had their revolvers, and at the first discharge the angry blacks seemed to waver, but still they came on. As in a dream Bob saw a wild, grinning face peering into his, while a heavy club was raised to strike; vainly he tried to lift his revolver, the blood rushed to his head, his brain reeled, another instant and the blow would have fallen, when, with a stifled cry, Jack dashed before him and sprang fiercely at the savage's throat. The very force of his onslaught bore back the gloating native, the club fell, but it fell harmlessly to the ground as Jack's fingers closed on its owner's throat. But the warrior had had enough; disentangling himself from the youth's grasp, with many a wriggle and gasp, he turned and fled, and when Jack looked round he found that the entire enemy had vanished.

"Now, boys," said Mackay, cheerily, "let us estimate the damage. You, Bob, have got an arrow-hole in your arm, an' I'm surprised you've managed to hold out so long, but if you had got that crack on the head that was meant for you, you would never have seen old England again."

Bob laughed weakly. "I'm pretty right," he said. "What about yourself?"

"Nothing serious, my lad; and you, Jack?"

"Not a scratch," responded that youth, brightly.

"As for me, boys," echoed out Emu Bill's voice dismally, "I'm a regular pin-cushion, I am. I reckon they've ventilated me a bit; but hang it all, them arrows don't hurt worth a cent."

But where were the Shadow and Never Never Dave? The former they found sitting moodily by the base of the mountain, his back propped against it for support.

"That there last rush 'bout finished me," he said. "A howling gorilla gave me a tender smack on the back wi' his club, an'—an' I believe it's broken."

Mackay laughed. "The back or the club, Shadow?" said he; whereat the sorrowful youngster arose painfully to his feet, and communed with himself in language deep and eloquent.

"Where in thunder has Never Never gone?" cried Emu Bill, anxiously, as they looked in vain for the well-known figure of the bushman.

"He was beside me when that last rush came on," said Jack, almost tearfully. "I didn't see what happened to any one after that."

"Dave! Dave!" cried Emu Bill, and there was a quiver in his voice which sounded strangely on his lips. "Where are you, Dave?"

Then a thin, weak voice answered out of the gloom by the ravine.

"I is right here, Bill, old man, right here."

And there they found him, lying aslant on the loose débris as he had fallen, an inert mass. His face was upturned to the sky, and his breath issued between his clenched teeth in long spasmodic jerks. He smiled feebly as they bent over him.

"I'm sent for this trip, boys," he murmured.

"Don't say that, Dave," groaned Emu Bill, in anguish; "you ain't goin' to leave your old comrade, Dave?"

Mackay knelt down by the stricken man and placed his hand over the feebly beating heart, and a hoarse cry of pain burst from his lips, which was echoed by the sad little group around.

"They must have given you a sair crack, Davie, man," said he, "a sair, sair crack."

Then he caught sight of the broken butts of two arrows in the sufferer's broad chest, and he turned aside with a heavy sigh.

"Never Never's going, lads," he said, with deep emotion. "Say your good-byes before it is too late."

Emu Bill gently pillowed his dying comrade's head upon his knee, and the tears ran down his rugged cheeks unchecked, and dropped upon Never Never Dave's pallid face.

"Good-bye, boys," he whispered, "don't fret 'bout me. I is goin' on a long, long trail, where there ain't no nigs an' no snakes. Never Never has made his last bush journey, I reckon. But—but—we reached the mountain." He ceased and laboured for breath, while the blood welled out from his cruel wounds with the exertion. Silently each pressed round and squeezed the bushman's rough and horny hand in a farewell grip. Once more the man whose life-blood was ebbing so cruelly fast away spoke, but now he was in the fantasy of delirium. "We'll get the spring all right, Bob. Don't worry, my lad—and the mountain, wi' gold and diamonds—we'll reach it, after all. Over the mountain—over—the—mountain." And so Never Never Dave went forth himself on a new quest with a smile on his lips, the smile of a man who knew no fear even at the end of his earthly pilgrimage. Emu Bill gathered the stiffening form in his arms, gulping down the great sobs with an effort, and tenderly he carried his lifeless burden over to the camp-fire, and sad indeed were the hearts of the melancholy procession which followed.

"I reckon Never Never has had his wish, anyhow," said Emu Bill, quietly. "He has passed in his checks with his boots on."

"May we a' go out on the long trail as bravely," spoke Mackay, solemnly. "Dave has gone over the mountain right enough. Over the mountain o' earthly difficulty and down through the valley of the shadow. We should not pity him now, boys, for he's free o' all the sorrows an' cares, an' disappointments o' this vale o' tears. But we mustn't forget the living, lads, though we respect the dead, or there may be more o' us starting out on the long trail before sunrise. Get a lamp, Jack, an' we'll have a look at that gully where they came out."

"You're right, Mac," answered Emu Bill; "I'll get a pick too, in case we need it."

The lamp was speedily brought, and they started over to the gully whence the natives had emerged, and as they crossed the scene of their conflict Jack stumbled over the dead body of one of the warriors. He shuddered painfully, and Bob, who was at his hand, drew him aside.

"There are three more of them, Jack," he whispered. "Never Never, hasn't gone under unavenged."

Mackay heard the words, and he laughed harshly.

"Ay, there's three more o' them, Bob," he said, "and there's a dozen more who feel a bit mair pained in their anatomy than we do."

They reached the treacherous ravine, and Mackay, taking the lamp in his hand, cautiously moved forwards and downwards into the deep recess, and gazed at the rocky rubble there strewn in bewilderment. In a moment Emu Bill stood beside him, pick in hand, but he too was nonplussed completely by the very natural appearance of affairs.

"I'll swear I saw them come outen this here hole," he said.

"We can't blame ourselves vera much for neglectin' to notice things," agreed Mackay, with a grim smile.

In the depths of the fissure which striated the mountain, only a number of loose boulders were to be seen.

"I reckon I'll try and shift some o' them," spoke Emu Bill. He stooped down and lifted one or two of the heaviest rock fragments, while Mackay held the light, and examined the markings on the walls of the cavern with keen interest.

"There ain't no opening here at all," cried Emu Bill, looking round fearfully, as if half expecting to find the savages still close in the vicinity. "I'm certain sure they couldn't get through here."

Mackay smiled. "I don't know what sort o' blacks we've struck, Bill," he said earnestly; "but if they constructed this trap-door arrangement they've got a wonderful amount o' intelligence."

He traced with his finger an irregularly shaped shelving crack in the southerly wall. It seemed a perfectly natural occurrence in every way, as indeed it was, but the edges gaped considerably towards the top, and Mackay, pressing lightly against the mossy front, caused the overlapping rim to close solid into the rock. By this time Bob, Jack, and the Shadow had scrambled in beside the two.

"But they couldn't get through that measly crack," protested Emu Bill, not quite understanding.

Mackay reached for the pick, and inserting the sharp point into the thin, almost unnoticeable crack now showing, pulled gently, and behold, the weighty rock swung back on end revealing a narrow, tunnel-like entrance penetrating into the mountain. At the same time a draught of damp and stifling air issued from the dark and gloomy passage way, extinguishing the lamp, and before they could look again, the rock fell softly back into position, and this time it closed with a snap. Again Mackay endeavoured to lever it open, but now the solid formation refused to be moved; try as he might, the doorway into the mountain seemed closed conclusively against him.

"Surely it cannot be a natural cave formation?" said Bob.

"Nary cave, Bob," returned Emu Bill, decisively.

"Not in a diorite rock," added Mackay, much perplexed.

They stood gazing at the tantalizing face of the ponderous doorway for some time without speaking. Then Mackay was aroused to action.

"We'll find out all about it before we go away from here," he said, "but in the meantime we'll barricade the swinging rock on this side to prevent any one coming out. I have an idea that it wasn't right closed at first or we would never have been able to find it; the blacks were in too great a hurry to be cautious, I'm thinking."

With a will they all set to work and built up a rampart of massive boulders in the ravine. Then they sadly went back to the camp-fire to await the coming of the dawn. All thought of sleep had left them now, and they sat moodily by the flickering flames for some time without a word being spoken, then as the chill morning air made itself felt, Bob's wounded arm, which he had not yet examined, began to grow stiff, and his head throbbed painfully. The Shadow, too, was far from comfortable, though he made no complaint, and he fought against his growing weakness manfully but at last, with a weary sigh, he fell back limp on his blanket. Then Mackay rose with an exclamation of regret.

"Bill," he said, "we've forgotten that these young mates of ours are scarcely as tough as we are. We'd better try an' doctor up their bruises a bit."

Emu Bill staggered to his feet with a sympathetic grunt, and walked blindly towards the camel packs in search of something that might serve for bandages, and Mackay stooped over the fallen Shadow and pulled back the neck of his much-torn shirt. The cause of that individual's relapse was not difficult to find, a great jagged gash on the young bushman's shoulder showed what a fierce blow he had received, evidently from a flint-studded club. Jack hurried to fetch water to lave the bloody wound, but the Shadow refused to receive any attention.

"Let the thing dry, boss," he said, sitting up once more. "I reckon I ain't no tender chicken to howl 'bout a muskittie bite."

Bob's memento of the affray was a little more serious; one of the barbs of the arrow had broken in his arm, keeping the wound open, and the blood was still dripping down his sleeve in great gouty drops. Mackay carefully cut out the splintered wood with the point of his sheath-knife, an acutely painful operation; but the patient never winced.

Then Emu Bill returned. "I can't find nary cloth 'ceptin' flour-bags," he announced. "Take a bit o' this here shirt o' mine."

He ripped off a sleeve of his garment and handed it to Mackay, and with it Bob's arm was soon tightly dressed. And now the rosy light of approaching dawn began to spread over the scene, and the stars faded out one by one before the radiant sun's advance. Morning had come at last. Yes, morning had come, and with it appeared in all their grim hideousness the evidences of the long night's struggle. There was Never Never Dave stretched beside them, his calm white face gazing peacefully towards the heavens. A little way off four huddled forms lay bent up in the dust, their torn plumes scattered around them. Here and there arrows and clubs were strewn, and gory tracks marked the way towards the subterranean passage wherein the warriors had retreated. Bob surveyed the ghastly relics with a sorrowful countenance. Here to him was a new aspect of the wanderer's life. In the pursuit of Nature's treasure the risks were many if the rewards were great. All was not sunshine and romance and pleasurable excitement. He stood for some minutes in silent contemplation.

"Yes," he said aloud, "and I, too, would have been lying there, had it not been for you, Jack."

"Don't speak about it, Bob," returned the boy at his side, with a shudder. "How could I have gone home without you?"

Mackay had, in the mean time, been examining the discarded weapons of the aborigines with critical interest.

"It seems to me," he said quietly, "that we might all have been lying there if the warriors hadn't imagined us to be asleep. I can only find about twenty arrows altogether. I think they could only have carried one or two each, never dreaming they would have need for more."

"I reckon that is why they tried to rush us every time," remarked Emu Bill. "They were too cock-sure, they were; an' we've got to be thankful for it. But ain't this a funny get up for nigs, even if they is on for a corroborree dance?"

He pointed to the strange habiliments of the dead warriors. Each native was cloaked in a rich opossum robe, suspended from the shoulders almost down to the heels.

"I can't make them out, Bill," said Mackay. "They are different from any tribe I've ever run across before. They're bigger than an ordinary native, and their faces look almost intelligent. But we've forgotten about the mountain passage. Surely the blacks couldn't have made that. There's more o' a mystery here than I can fathom, Bill; but we'll soon know what it all means."

"I just reckon we will," grated Emu Bill as they turned away.

Jack, who was now the most active member of the party, was not long in preparing breakfast, and the stimulating influence of the boiling tea did much to revive their weary spirits.

"If only Never Never hadn't gone under," said the Shadow, as he munched at his hard, unpalatable damper fare, "I could have felt real joyous, I could. I reckon we has struck the land o' gold and di'monds right enough."

The mysterious mountain had assuredly grown more and more mystifying. What wonderful secret could be hid beyond? What strange people could have made the tunnel through its mighty heart?

"I am convinced we are about to make a wonderful discovery," said Bob. "Ordinary aborigines could never have constructed that passage——"

"And allowing that they could," interjected Jack; "what purpose is it supposed to serve?"

"I reckon it's the treasure chamber o' the Never Never we has struck at last," observed Emu Bill, with quiet assurance. "Nary man ever knew what to expect in this here country; but we has struck the secret, only poor old Dave ain't with us no more."

There was no doubt that the expedition had reached a region of strange mystery in the heart of the great unknown land of the Never Never. Their humble repast over, there now came the sad duty of interring the body of their dead comrade. Silently they filed off, armed with pick and shovel, in search of a soft spot in which to dig the grave. But no kindly soil was to be found; the bare rock appeared everywhere immediately below the surface.

"There's only one thing we can do," said Mackay. "We must drill and shoot a hole down wi' gelignite, that is, unless we carry poor Dave out across these springs into the desert, but for my part I'd rather bury him close into the mountain. I think he would have liked it himself. Let us give poor old Dave a big monument, boys, I'm sure none o' us will grudge the work."

Grudge the work? Not they. It was the last tribute they could pay to the faithful and brave companion of their travels, and with heavy hearts they set about their task. A case of gelignite had been included in the outfit of the expedition in anticipation of any valuable ore deposits being found which might necessitate blasting before samples could be obtained, and now for the first time the deadly explosive was called into requisition, and for a most melancholy purpose. The long steel drills which had done such good work in the Golden Promise Mine were also called into play, and all forenoon Mackay and Emu Bill laboured at their sad work, relieved occasionally by Jack, the Shadow, and Bob, for though the last two were then wholly unfitted for any exertion, they insisted on taking their turn, Bob swinging the great hammer with his one free hand, while the Shadow held and turned the drill. At every half hour or so the mighty roar of an explosion would burst forth from the rocky excavation, and a hail of boulders and showers of iron sand were hurled into the air.

In the midst of this turmoil Bob happened to look up, and he was scarcely surprised to see the same gloomy figure on the mountain summit watching their operations intently.

"I can understand his warning now," he muttered to himself. "He knew they were going to attack us from the tunnel. But why should he have wished to save us?"

The more he considered the matter the more puzzled he became. Then he observed quite a number of the oddly garbed natives join their companion on the hilltop. Again and again the dull boom of the heavy gelignite charges echoed out on the still air, and after each ponderous report a fresh group seemed to gather up aloft until Bob could count fully fifty of them.

"I reckon this here circus sort o' disturbs them," grunted Emu Bill.

Mackay looked anxious. "I hope there's no more o' them," he remarked gravely. "We've struck a bigger-sized tribe than we calculated on, Bill, an' we'll have to be vera cautious."

At last the tomb was completed and reverently they wrapped the dead man in his blanket and carried him to his last earthly rest. No tears now dimmed their eyes, their sorrow was deep set in the heart; it had passed the mere emotional stage, and could find relief only in strenuous action. Then they stood around the open grave with bowed heads, while Mackay repeated a brief prayer. Long afterwards Bob remembered the quiet dignity of his utterance, the simple eloquence of his tribute, and the whole pathetic scene would return to him with all its overwhelming memories. When he had finished, they shovelled in the loose sand and rubble in solemn silence, and built up a cairn over the top.

The natives from their position of vantage had gazed stolidly down on them throughout the entire ceremonial; but now they dispersed, leaving but one solitary watcher on the height.

"We'll have to plant these natives now," said Mackay; "we can't leave them lying like that."

They walked over and surveyed the bodies again, and the Shadow taking the long opossum robe from one of them, threw it over his own shoulders with a chuckle of satisfaction.

"I reckon this here ornament should just fit me," said he, turning round for inspection.

Emu Bill laughed hoarsely. "Throw the wretched thing away, Shad," he growled. "Ye doesn't want to wear a nig's wardrobe, does ye?"

But a wild idea had just then entered Mackay's head; he bent down and gathered several of the emu feathers lying around; these he stuck in the Shadow's hair much to that youth's disgust.

"Why, Shad, if your face was blacked you'd pass for one of the warriors!" exclaimed Jack, noting the effect at once.

"We'll save these decorations for future use," said Mackay, quietly.

Emu Bill whistled softly, "I never thought o' that," said he. "I reckon it's a real daisy idea."

Quickly they despoiled the natives of their gorgeous trappings, and Bob sighed when the miserable bodies were revealed in all their savage nakedness, and marvelled at the unusual muscular development showing in their chest and limbs.

"Ay, Bob," said Mackay, guessing his thoughts, "one of these fellows is worth two of any other tribe, I ken. Somehow, though I have a sair grudge against them, I feel sort o' sorry to see such bonnie specimens slaughtered."

"But I reckon they would have danced round our funeral all right," said Emu Bill, savagely. "Hang it, the nigs in this here country ain't fit to live, they ain't."

"There are no opossums about here, are there?" asked Jack, suddenly.

"Nary one," answered Emu Bill, with a laugh. "Why, they couldn't live on sand, an' there ain't no trees around that a muskittie couldn't bend by sitting on them."

"Then where could these skins come from?" cried the lad.

Bob shook his head dubiously, and Emu Bill seemed to have thought of the matter for the first time. Mackay alone seemed confident in his knowledge.

"It's a sure proof, Jack," said he, "that beyond the mountain there must be a different kind o' country, a country o' forests and rivers, maybe, and our Eldorado."

CHAPTER XV The Secret of the Mountain

It was well into the afternoon before their gruesome task was accomplished, and the sun shone far down in the Western sky when they returned to the camp. They had carried the deceased warriors out into the sandy tracts beyond the boiling springs. It cannot be said that they were unduly sympathetic with the slain, and certainly they were anything but enamoured of their self-imposed contract, but the alternative would have been extremely disagreeable.

"I have no doubt their brethren would have come for them to-night," said Bob, "and saved us a good deal of trouble—if we could only have depended on them going peaceably away again."

"Ay, if," agreed Mackay, dryly. "But their coming would only mean more funerals, Bob, and as for that, I believe they've been trying to force that patent door of theirs before now."

He turned and gazed towards the fissure at the base of the mountain, and at that moment there distinctly came a sound therefrom as of the jarring of rocks under pressure. They all kept perfect silence for a minute or two, and again the sound was repeated, but this time it was succeeded by the sharp rattle of falling boulders.

"That's the top o' our barricade down, I reckon," whispered the Shadow, reaching gingerly for his rifle.

"They would see us go out into the plains," hazarded Bob, calmly, "but the smoke of these very convenient boilers has kept them from noticing our return."

Mackay nodded. "They've got about a solid ton to shift before the door will swing," he said musingly. "Now I wonder if we should go an' help them wi' the job or no'?"

"I reckon we has had enough for one day, Mac," answered Emu Bill, wearily. "Let the skunks work their own passage."

Another rattle, louder than the first, reached their ears.

"'Pears to me they is in a mighty hurry," grinned the Shadow.

Bob rose to his feet. "I'm going to have a look," he said. "Come on, Jack;" and they tip-toed over to the origin of the disturbances, leaving their companions apparently deeply and solely intent on bringing the billy on the fire to a boil speedily.

Mackay had examined the barricade once or twice earlier in the day, and noticed no change in its appearance, and was convinced that nothing short of gelignite cartridges could shift their obstruction from the inside. Bob held the same opinion, but he was nevertheless curious to see what sort of efforts were being made. Making a short détour, they silently approached the entrance to the underground passage from the side farthest from the movable rocky slab. The interstice had been well-nigh filled with diorite boulders, leaving only the top of the solid panel showing; but when Bob looked now, he was alarmed to find a considerable shrinkage in the level of the barricade, and though the noisy echoes of falling rocks were still plainly heard, it was evident that nothing was rolling down from the top of the pile. Jack drew a quick breath of anxiety; Bob was perplexed beyond measure, but he made no sign, and as he looked, behold! the boulder stack was gradually, yet surely, sinking—sinking apparently into the earth beneath. Then his eye noticed some slight change in the position of the rocking wall; it was thrust up somewhat, and gaped widely. The solution of the mystery was now made clear: the great slab moved upwards as well as outwards, and the depletion of the pile was taking place from the bottom; the rock fragments were rolling inwards to the tunnel!

Hastily he beckoned on his companions, and they came forward at a run, just as the last stone was disappearing from view. But the natives had now taken alarm. There came a dull thud as the doorway relapsed into its accustomed place, and then their rapidly retreating footsteps were heard as they scurried back into the subterranean channel, and the peculiar tapping of the night before heralded the direction of their flight.

Mackay took in the position at a glance, and an expression of grave concern settled on his features.

"Their resources are positively marvellous," he groaned in despair. "It's a vera fortunate thing, Bob, that you werena influenced by my stupid over-confidence, and came to investigate. We might have been bowled over wi' their arrows before we had time to lift a rifle." He continued bitterly to abuse himself while he inspected the now bare cavity in the mountain.

"I reckon it's a long sight more fortunate that they came along in the daytime," commented Emu Bill, "which they likely wouldn't have done, if they had thought we were about. Seems to me, that good Samaritan job o' ours in planting them nigs nice and comfortable out in the sand has done us a service right away."

"You've hit it pretty near, Bill," Bob agreed. "If they had done that trick in the night, we should probably have been wiped out."

"This is a mighty unpleasant climate for us tender lambs, it is," wailed the Shadow. "There's nary night but what we may wake up wi' a screech an' find ourselves dead."

"There's one way we can block it for good," muttered Mackay, grimly, "but I'm no vera willing to do it, for it will block us too, an' I mean to get inside that mountain before I'm a couple o' days older." He looked towards the gelignite case, lying near where it had been placed for safety, and his companions knew his plan at once. "Yes, we may well shoot down a bit o' the mountain big enough to bar that tunnel safe as a house, but that wouldn't suit us afterwards."

"If we roll round a few boulders wider than the door itself, that would keep things pretty safe for a night," suggested Jack; and in the end, this was the plan decided upon, and for half an hour they busied themselves transporting the most unwieldy diorite blocks they could find, and fixing them securely into the cavity. Then they returned to partake of their well-earned and belated dinner of tea and damper.

The last added proof of the blacks' ingenuity considerably disturbed the members of the little party. It had been so hard to believe that aborigines could possibly have constructed the tunnel through the mountain, but now they were inclined to imagine their savage neighbours capable of anything.

"I reckon we has got to go slow, boys," remarked Emu Bill, with a troubled expression; "them nigs don't seem to be the genuine article. They knows a long sight too much for my liking, they does."

Mackay, too, was obviously concerned. The mysterious tunnel mystified him; he could not imagine how it had been wrought, but there was gradually dawning in him a vastly increased respect for the natives who lived beyond the mountain. That they were different from all other tribes he had encountered was only too evident. The question was, in how great a degree did they excel their brethren of the plains? Judging from his brief experience of them, Mackay's estimate of their powers was far higher than he cared to admit.

"Of course," he said, in answer to Emu Bill, "if the country on the other side is what we expect, the natives will be of a much more advanced class than any we've met before. You see, it's the power o' environment, Bill; it may have worked marvels here, for a' we know."

They ate their unpalatable meal without much further remark. Then Bob, who had been pondering deeply over the events of the last twenty-four hours, showed the trend of his thoughts by asking quietly if any of the aboriginal tribes had been known to use bows and arrows.

"I never saw, nor heard tell o' such a thing before," grunted Emu Bill.

"In that case," said Bob, "these natives show that they have originated that custom here, or have retained it from an earlier period, before the blacks began to degenerate; and, in either case, it proves them to be an exceptional lot altogether."

"That's just what's bothering me, Bob," admitted Mackay. "We might well tackle an ordinary tribe, even though we only numbered five against fifty, but wi' these beggars here, I'll allow we seem to be embarking on a job that is, to say the least of it, a bit unhealthy. No, no, don't think I'm gettin' nervous, Bill, but we must calculate the chances before we start. Bob counted fifty niggers on the hill this morning, so we've a fair idea o' what we are goin' to run up against."

"Hang it, boss," complained the Shadow; "you doesn't think a crowd o' nigs is goin' to hustle us back now, does ye? If we kin join their happy family in the daytime we'll scatter 'em quick an' lively, but the night gives me the creeps, it does. I can never see the sights o' my rifle in the dark."

"If we were once on the other side of the mountain," said Jack, eagerly, "we could soon shift the blacks; it's the wretched old tunnel that keeps worrying us here."

"Ay, my lad," said Mackay, dryly; "the tunnel is a vera curious construction for a crowd o' aborigines to make, an' the more I think about it, the more puzzled I become. I was going to suggest that Bill an' me should force the passage in the morning, while the three o' you waited out by the camels in case o' accident."

"I'm right wi' you there," cried Emu Bill. "I reckon it ain't safe for these here young 'uns to come along wi' us first——"

A storm of protest greeted his words, and Bob turned to Mackay reproachfully.

"I know what you mean," he said; "but neither Jack nor I will leave unless we all leave together, so that if anything happened to you we would not escape in any case. Isn't it far better to make the most of our strength instead of dividing it?"

"Well, well, perhaps you are right," returned the big man, hastily, as if annoyed at his own fears; "but we'd better wait until morning before we start the circus. Like the Shadow, I prefer to meet the natives in daylight, and anyhow, we're a' needing a sleep to-night, so we'd be better to turn in early and get up by sunrise. It should take us a good half-hour in the morning blowing out that tunnel door for a start."

Certainly nothing further could be done on that day, for the darkness was already closing in, and each one of the party was weary and tired from lack of sleep. So shortly afterwards they lay down in their blankets, though not before a searching examination had been made of the new barricade erected at the entrance to the subterranean passage, and, in spite of the known dangers surrounding them, they slept soundly, each taking a two hours' watch in turn. It was well after midnight when Bob awoke for the first time, and at once his ears caught the strange tapping in the mountain which had first heralded the approach of the natives on the night before. He aroused himself immediately, and saw Mackay, who was on guard, listening to the ghostly echoes intently. Slowly they seemed to pass along the base of the hill, then all was quiet. Bob got up and joined Mackay, and together they walked softly towards the fissure, and there in the dull light they could vaguely see the great boulders move as if under pressure from beneath, but though they watched for fully ten minutes in silence, the barricade remained intact. Jack's scheme had worked admirably. Then Mackay turned on his heel with a loud laugh.

"It's just as well to let them ken we're here, Bob," he explained; and the sound of scurrying footsteps which answered him from the concealed passage showed that the natives had thought fit to retire once more. Then again the peculiar tapping issued out dully from the great rock, continuing for nearly a minute before it faded into the stillness of the night.

"Well, what do you make of it, Bob?" asked Mackay.

Bob did not hesitate a moment. "The passage must lead for some distance along the face of the mountain," said he. "But why these strange sounds are heard every time the blacks come along, I cannot say."

"Man, Bob," laughed Mackay, "that's vera easily explained. The tunnel must be dark, of course, and the warriors have to guide themselves along the passage by feeling the walls wi' their arrows or clubs as they go. It just struck me that that was the reason o' the uncanny noises when I heard them come along there to-night. Simple enough, isn't it, Bob?"

"I'm glad there is nothing approaching the supernatural about it, anyhow," replied Bob, soberly. "The echoes seemed to ring in my ears like a knell of doom."

He shuddered as he got back into his blanket. The others were awake by this time; but when they learned that an ineffective attempt had been made to destroy the barricade, they chuckled in rare good-humour, and went off to sleep again. The remainder of the night passed without alarm, and the morning broke, calm and serene, over the little camp, which awoke to life with renewed vigour after its peaceful slumber. Breakfast was soon over; then a hurried council of war was held to reason out the best plan of action. Emu Bill was in favour of inserting a heavy charge of gelignite in the rocking panel which had defied their gentler efforts on the preceding day; and Jack and the Shadow supported this proposal vociferously. Mackay, however, though he had at first advocated this drastic action, now seemed reluctant to carry it through; and Bob, too, though he did not say much, was evidently pondering over some other and better scheme, which he at last broached hesitatingly.

"If the passage runs parallel with the face of the mountain for twenty or thirty yards," he said, "it strikes me that if we made a fresh entrance to it as far away from the old one as possible, we could deceive the natives most completely, and perhaps provide a means of escape in an emergency."

"I don't quite catch on," grumbled Emu Bill. "I'm hanged if I see what difference it should make; an' we doesn't know how far we'd have to dig into the blasted rock afore we hit the tunnel—if it's where you say."

Mackay took up a pick, and, proceeding along the base of the mountain away from the fissure, struck at the rocky wall repeatedly, with the result that a deep, hollow rumbling issued forth at each stroke, until a point had been reached some thirty yards distant from the tunnel entrance, when only the solid diorite formation gave back the sound.

"I calculate we'd have less than five feet to drive, Bill," said he. "About a couple o' long shots in from the top would do it. You can trace the passage as plainly as if you were looking at it. I don't know what the idea was in making it like a boomerang; but we'll soon find out. Now, Bob, you're better at explaining than me. Try an' convince Bill o' the advantages we may derive from making a new hole into the mountain."

"I reckon I can see it all right," cried the Shadow. "Oh, it are a daisy——"

"Shut up, Shad," growled Emu Bill. "Now, Bob, for any sake, tell me your plan. Of course I'm with you, whether I understand or not; but, blow me if I can see the force o' doing extra work in the niggers' mountain fur nothin'."

Then Bob endeavoured to elucidate the ideas which had been taking shape in his brain all through the night, since Mackay and he had come to a conclusion as to the origin of the warning sounds and the proximity of the passage for some distance to the outer air.

"If we don't tamper with the old door, boys," said he, earnestly, "we can block up the hole we make by some bagging, and so will always have a chance of escape if the natives are too many for us. They will guard their own entrance only, for they probably will never see ours; and it's just as well to take precautions. The darkness of the tunnel will help our plan; and if we succeed without having to trouble about getting back, so much the better——"

"And there are a few more arguments in favour o' the scheme, Bob," added Mackay; "but we may see the excellence o' them later."

"But they'll hear us firing the charges, won't they?" said Jack.

"They heard us doing the same thing yesterday," answered Mackay; "an' they saw us too, so it's no vera likely they'll trouble us to-day. But if we put the drill-holes in deep enough, and give the powder plenty work to do, there shouldna be much noise—in fact, I doubt if they'll hear it at a'."

No time was lost in making the experiment, and the long steel drills were quickly grinding their way through the hard outer casing of the rock as nearly as could be judged opposite the place where the passage took an abrupt turn inwards. And now the mining knowledge of Mackay and Emu Bill made their work comparatively easy; they knew exactly the correct angles at which to drive the drills so as to obtain the best results when they loaded the holes so made with the deadly explosive. Steadily they laboured at their task, Bob, Jack, and the Shadow assisting at intervals, but more often engaged farther out in the open making a goodly appearance for the benefit of the natives, should they chance to be watching, and thus drawing attention away from the great work in hand. For a full hour Mackay slogged at the steel with his mighty hammer, then gradually the borings extracted from the deepening hole grew lighter and redder in colour, and the drill sank inwards rapidly.

"That's a new formation we've struck, Bill," said he, pausing to examine the edge of his tool. Then an exclamation broke from his lips. "We're chippin' through a gold lode!" he cried; "and it's so rich that the drill clogs in the metal."

"I reckon there's nary nig'll shift us from here now," said Emu Bill, examining for himself the gold grains exposed. "I means to see the other side o' this here mountain, or bust. I reckon there must be oceans o' gold an' di'monds over there."

At this stage Jack called out warningly, "I see old Nebuchadnezzar on the top of the mountain again."

"It's the same old nig that we didn't shoot," exclaimed the Shadow; "an', blow me! if he ain't goin' to throw stones at us."

The tall figure on the summit had certainly attempted to throw something down; but it caught on a jutting rock overhead, and bounded thence into the rising vapours of the hot springs. Once more he appeared to cast some projectile into the air; but if he did, it did not reach the ground in the vicinity of the anxious party beneath. Then again a visible missile came hurtling down; but it fell wide, much to the Shadow's satisfaction.

"The old fool can't throw stones for nuts!" he cried delightedly.

"I don't think he'll hurt us much," said Mackay, with a laugh. "Let him play away, Shadow, if it amuses him; it doesn't do us any damage."

And the individual aloft continued his strange pranks for some time, though in no one instance did the stones he threw alight even moderately near; then he vanished as suddenly as he had come.

"I think we're about ready for firing, Bill," said Mackay, shortly afterwards. "We'd better hurry up, too, seeing that there does not seem to be any one about to watch in the mean time."

The drill had been driven over eight feet down, at an angle of somewhat less than forty-five degrees, and Bob, making a rough calculation, considered that its extremity was at least four feet away from the surface of the rock in a straight line.

"We'll give it twenty-five cartridges, I think," mused Mackay, "an' the shock o' discharge should burst at least another foot inwards."

"I reckon something's bound to shift," murmured Emu Bill, as he deftly prepared the charges, and inserted the long fuse.

Bob watched the last operation with quiet interest, but not so Jack and the Shadow. They suddenly pranced off towards the cooking utensils by the fire, and began to drag them back out of range.

"Tea and damper is bad enough," groaned the Shadow, tenderly secreting the only two billy cans the expedition possessed; "but damper without tea would be howlin' starvation, it would."

"You doesn't need to worry, Shad," grinned Emu Bill. "There won't be much o' a scatter here."

And he calmly applied a lighted match to the end of the fuse, and stood for almost a minute, listening to its sputtering as the fire crept slowly down towards the gelignite, before he turned away. Another minute, two minutes, three minutes passed.

"I'm afraid we've had a misfire, Bill," said Mackay.

But just as he spoke the base of the mountain seemed to quiver and burst forward, then came a dull report, and when the smoke cleared away, a giant crack showed in the rock, but otherwise no evidences were left to indicate that a powerful explosive had been at work.

"That's hard lines," said Emu Bill, stepping forward. "It might have shifted that chunk o' iron out o' the road, anyway. Now we'll need to begin all over again."

"I'm no so sure o' that," answered Mackay, waving his hat in the rent created in order to dispel the clinging white fumes, which obscured all vision.

Then it was made apparent that it was no mere crack in the formation they gazed upon. The force of explosion has not only cleft the rock, but had thrust it almost a yard forward in one unbroken mass, and at the bottom of the chasm thus made a vague blackness appeared, the blackness of a void. Mackay bent down his head eagerly, but hastily withdrew it again; a rush of heavy damp air, stifling and odorous, had come with a gust in his face.

"I reckon them powder fumes'll make you feel pretty bad," sympathized Emu Bill. "Just give the smoke time to clear, Mac, an' then we'll put in another shot."

"There's no need to do any more work here, Bill," answered Mackay, recovering himself. "We've broken right into the tunnel first pop! There it is, too, as natural-looking an entrance as you could wish to see, wi' a door—if we could move it—that weighs five tons if it weighs a pound."

Eagerly they all clustered round to look; and now that the atmosphere had grown less clouded, the dark shadows of the cavern below were plainly discernible. Bob gave a sigh of relief. At last the secret of the mountain was to be revealed.

"Well, I reckon I'd better get down an' prospect round a bit," said Emu Bill, hitching up his nether garments preparatory to scrambling down into the uncertain depths.

"Let me go first," urged the Shadow. "I'm the lightest, and it wouldn't hurt me much if I did go down a bit further than I expected when I let go the edge."

"We'll lower a rope wi' a stone on the end o' it before any one goes down," said Mackay, firmly. "We've got to engineer this funeral vera cautiously, my lad, an' mustna go bouncing ourselves into difficulties, as if there was a good fairy waiting by us every time to pull us out o' them."

A rope was speedily forthcoming, and fastening a fragment of rock to the end of it, Mackay carefully allowed it to descend. It came to a standstill in good time, however, showing that the bottom of the passage was barely three feet below the point where the rent had entered its wall. Mackay quickly proceeded to adjust the rope so that its extremity dangled just on the edge of the yawning gap, then he made it fast on the outside by coiling it several times round the top of the sundered rock.

"A man could pull himself out in a hurry by getting something to hold on to," he remarked, "an' it's just as well to be prepared."

This operation completed, Emu Bill wriggled himself down through the narrow opening, and holding on to the guiding-rope, quickly disappeared from view, while his companions on the surface waited expectantly for his report on his surroundings.

"Well, an' what do you make of it, Bill?" demanded Mackay, when the tension on the cable had slackened.

"I can't see a single thing," came the response. "It's dark as—as Hades, an'—howlin' blazes! but it does smell."

Without a word Mackay slid down beside his complaining comrade; the Shadow followed, then Jack, and lastly Bob squirmed down beside them. All was dark and oppressively gloomy in the strange passage, and the thin streak of light from the opening they themselves had made, only served to intensify the utter blackness which prevailed. They stood for a full minute without speaking, their ears alert for the slightest sound which might warn them of danger; but all was silent as a tomb.

"Now, boys," whispered Mackay, "we'll have a look at the inside o' that other doorway before we go any further." He led the way, staggering and stumbling, and Bob, following at his heels, became conscious that the floor of the tunnel was extremely muddy and wet. After a few steps Mackay paused. "I've got a bit o' candle in my pocket," he said; "I may as well strike a light."

The match spluttered feebly in his hand for a moment, and then went out, but on a second attempt he succeeded in getting the candle alight, and though it burned with a dismal blue flame, it illuminated the rocky cavern sufficiently for the adventurers to observe its structure.

They stood in a longitudinal chamber about eight feet high, and barely four in width. The roof fairly scintillated with beaded moisture, and the dank, cold walls were adrip with ooze. The bottom of the chamber, as they had already discovered, was a soft and clinging clayey formation. Mackay's trained eye immediately grasped the significance of the scene.

"This is a most extraordinary thing to find in the heart o' Australia," he said. "It's a tunnel driven through an enormous gold lode, an' it's vera evident that the men who made it knew almost nothing about mining, for the ore hasn't been stripped either to the hanging wall or foot wall. It's just as if a blind gap had been dug into the country where it was softest."

"I see a nugget shining in the roof," whispered Jack, pointing to a yellow splatch showing overhead.

"Ay, my lad, an' I can see several more," said Mackay, surveying the exposed stratum in bewilderment. "It is a wonderful mine, without a doubt, but what on earth the natives do with it is more than I can imagine."

He moved onwards once more, and then he halted suddenly, and held the candle aloft. The passage had come to an end; before him stood the huge stone panel which had first barred their entrance; at his feet gaped a deep, pit-like cavity.

"Come close up here, Bob," he said quietly. "Come an' have a look at this arrangement o' things; primitive but effective, eh?"

Bob gazed at the sight before him in absolute wonderment. The great stone which marked the end of the chamber stood upright on an egg-shaped base; it appeared to be formed like a rude and bluff wedge, the wider extremity protruding outwards, where, as had been seen, it flanged neatly on to the main rock from which it had sprung. But it was not its shape that surprised Bob: a massive bar of some gleaming metal was welded into it fully halfway up its height, and from this U-shaped bar a rope of extraordinary girth stretched taut into the depths of the pit, where it could be seen attached to a ponderous mass of diorite rock, which hung from it like the weight of a giant clock.

"It must take more than one man to open that door," murmured Jack.

"They probably always come in force when they use this passage," mused Bob; "and see, I suppose that arrangement is for keeping the stone bent over when they are out?"

He pointed to a short and stout log lying near, which had apparently been used for preventing a quick rush back of the weighted panel when the warriors had gone out on the night of the conflict. Mackay stepped gingerly across the intervening shaft, and shone his light into its unsavoury depths as he did so.

"I see now where our boulder barricade dropped to," he said; "but I can see also that they can never move our present obstruction in the same way, the big blocks outside will stick them, no matter how they try."

Emu Bill now tried to find his speech. "How in thunder is we to account for the rock prizing open wi' us at first?" said he. "I can't understand this here concern yet, I can't."

Bob pointed downwards to where the wall of the pit was deeply scarred and dented.

"Likely enough the weight caught in the side," he said, "and so eased off the tension considerably."

Mackay, who had been keenly scrutinizing the rope and the stout bar in the stone to which it was connected, now lifted his head.

"The rope is made o' a grass which doesn't grow on our side o' the mountain, boys," he said; "but the bar is fashioned out o' a metal which is known to all of us, though we've never managed to possess it in sufficient quantities to throw away on a job like this, where simple iron would be far stronger and better in every way."

"Why!" exclaimed Emu Bill. "You doesn't mean to say that they've stuck a chunk o' gold in that there stone, does ye?"

"I just do," answered Mackay, wearily. "Now, I think we'd better get out and think over things for a bit. Two or three shocks o' that sort would just about destroy my nervous system altogether."

"But you ain't goin' to leave that bonanza in the rock, surely?" cried the Shadow. "Let me get one tug at it, boss, I'll pretty soon yank it out, I'll——"

But here his companions gently but firmly led him away.

"There's bound to be lots more of it lying around," said Jack, soothingly, as they retraced their steps.

When they reached the exit the light of the candle showed them that the tunnel here swung off to the left at a right angle, and at this point the passage was considerably wider than they had at first judged, probably owing to the difficulty the natives had experienced in making such a sharp turn. But the eye could distinguish nothing beyond the radius of the feeble illumination; all was oppressively murky and damp and repellent.

"That's our road, boys," said Mackay, pointing with his candle into the gloomy cavern which led into the heart of the mountain. "But before we start on our journey we'll get out an' make our final arrangements, an' change our wardrobe to suit the situation."

In a few minutes they were all on the surface once more, eagerly talking over their prospects, for, strangely enough, the dangerous aspect of their projected journey through the mountain was for the moment lost on them, so completely had the glamour of the golden tunnel exercised its subtle influence. Mackay, however, quickly regained his control.

"We must remember, boys," he cautioned, "that we have no ordinary natives to contend with, an' before we leave this camp it will be necessary to attend to some details which may be helpful to us afterwards."

"What would you suggest?" asked Bob.

"In the first instance," Mackay replied, "we should hide the camel-packs containing our provisions. We can easily do that out among the sand on the other side o' the springs. It won't take us half an hour altogether."

"But what about the camels?" interjected Jack.

"They are a good distance away, my lad, an' they're no' hobbled. They'll just have to take their chance; but I don't think there's much risk in that direction, after all, for Misery can't stand the sight o' a nigger, an' if he bolted, the rest would follow, an' we could track them up afterwards just as I had to do before in this same district."

It was yet early in the day, and though Emu Bill was loath to delay their tour of discovery even for five minutes, he was brought to see the wisdom of Mackay's advice. Within half an hour the camp had assumed a bare and desolate appearance, only the heavier mining implements being left at the base of the mountain. Then they gathered round the cleft in the rock, and hurriedly prepared for their work of subterranean exploration. It had been agreed that the party should don the robes of the deceased warriors in order to lessen the chances of detection should any natives be encountered while traversing the mysterious passage, but now they saw that whereas there were five persons to transform into savages, there were but four of the long furry coverings, although the feathered decorations for completing their sartorial equipment were more numerous than necessary.