"Things are beginning to look lively," said Bob, adjusting his cartridge-belt.

Jack ranged himself quietly by his comrade's side, his rifle gripped in readiness.

"I don't know how this is going to turn out, Bob," he said slowly; "but I mean to shoot straight, to-night."

"It's a case o' self preservation, my lad," warned Mackay; and he closed the breech of his powerful weapon with a vicious snap. "You needna think o' usin' the stock o' your gun in this scrimmage. I am just afraid it's goin' to be more serious than I thought."

There could be little doubt as to the meaning of the wily natives' tactics. Assuredly they intended to surround the little camp, which they considered to be safely asleep, and spear the party at their leisure.

"We are to be their sacrificial offerings, apparently," remarked Bob, with forced calm.

Mackay was aroused to a sudden burst of fury at the words; his long-smouldering anger against the natives effervesced to an alarming pitch.

"I'll give them sacrifices," he grated, peering into the darkness with eyes that seemed like glowing coals of fire over the gleaming barrel of his rifle. "I'll make them think an earthquake has broken loose in their midst. I'll—I'll——"

Indignation choked his fiery utterance, and he said no more, but toyed lingeringly with the trigger of his gun.

A minute elapsed, it seemed an eternity, but no signs of the enemy could yet be traced. Instinctively Bob's eyes returned to the recent centre of affairs where the impish fire feeders were heaping on the logs with frantic glee, and he shuddered involuntarily. The suspense was rapidly becoming unbearable, and the little band expected every moment to be overwhelmed with flying spears from some unlooked-for corner. Each pigmy bush around to their overstrained vision took on the appearance of a crouching warrior, and it was with the exercise of great restraint that Mackay and his comrades refrained from firing at random into the night. Slowly the seconds dragged their weary course, then all at once a weird unearthly chorus reached the ears of the anxiously waiting group; it seemed to come from everywhere around, and they turned about in dismay. The attacking horde were closing in on them from all points of the compass. Only when the ring had been completed had they begun their deadly advance. Neither Mackay nor any of them had expected this.

"I reckon we is bested, mates," groaned Emu Bill, helplessly; and it certainly did seem as if he spoke truly.

Another minute elapsed, then they grounded their arms in impotent rage; the swelling chant from an unknown number of throats was drawing insidiously nearer, and they could only roughly guess the various origins of sound. Mackay turned to Jack to give a last word of encouragement, and he was surprised to find the boy standing by Bob's side in an attitude of acute attention—his head was bent forward, and he shielded his ear with his hand as if he were listening intently.

"I've got them," he whispered eagerly. "Unless there's a dummy musician in their ranks, there's a fifty yards' blank in the circle straight out by the camel packs."

"How many do you make altogether, Jack?" inquired Mackay.

The boy replied promptly, "They seem to be about thirty yards or so apart. They are nearly two hundred yards off now, and coming very slowly. There must be nearly fifty of the beasts."

"Good for you, Jack," murmured Mackay, heartily, a tribute of praise which even at that moment Emu Bill and the Shadow echoed with characteristic vehemence.

There was no time to be lost, the fateful ring was closing every instant; so, gripping his rifle tightly, the leader of the expedition made a course out in the direction as indicated by Jack, his comrades following after in Indian file. And as they passed out by the camels, each man breathed a prayer for their safety; then, with the hideous voices of the approaching warriors ringing in their ears, they made their way stealthily out through the saving gap into the freedom beyond.

Surely never before had a course been steered by such odd reckoning, yet the droning cries on either side of the escaping party as they neared the edge of the invisible circle guided them as well as glaring beacons would have done, and they manœuvred cautiously through the midst of the fervently singing band, luckily escaping all observation.

"It was like navigatin' through the Heads of Sydney Harbour," exclaimed Emu Bill, flinging himself down on the sand immediately they had cleared the dangerous line.

"We've got to thank our stars the beggars have the good sense to say grace before supper," said Jack, cheerfully.

"We are no' just altogether out o' the difficulty yet," warned Mackay. "They'll be back with a rush when they find out their mistake."

"But you ain't goin' to let them run the whole circus, surely?" complained Emu Bill. "Let's pepper the howlin' dervishes now."

Mackay seemed to hesitate for a moment, the odds in numbers were greatly against them.

"Train your guns on the old camp, boys," he said quietly. "You'll see their black bodies against the glow o' the ashes when they get nearer." He had scarcely spoken these words when the dismal chant of the over-sanguine natives ceased, and with blood curdling yells the savage horde swept on to their supposed work of extermination. The onlookers saw a perfect hail of spears strike and quiver amid the smouldering ashes; then a fantastical array of fiend-like forms swarmed before their eyes, and prolonged shrieks of baffled rage rent the air. Now was their opportunity. "Fire, boys!" cried Mackay, himself setting the example; and the death-dealing weapons thundered out their grim challenge to the foe. When they looked again only a fiercely struggling mass of black humanity was visible, and the scattering sparks showed where the shots had taken effect. Once more a well-directed volley was poured into the surging crowd; but this time the flash of the rifles betrayed their presence, and immediately about a dozen gaunt apparitions charged down on the little party with vengeful shouts. It looked as if nothing could stand against that maddened rush. In vain the rifles spoke, the members of the attacking band seemed in no wise to diminish, their figures could only be vaguely traced in the gloom.

Bob, plying his almost red-hot rifle, checked himself at the words, and calmly obeyed the instructions given; Jack, panting furiously with his extreme exertions, grounded his loaded weapon and waited with something like a gnawing despair at his heart. The Shadow grumbled incoherently to himself, Emu Bill and Never Never Dave said not a word, but stood erect, calm, and motionless beside Mackay, awaiting the shock. Then a strange thing happened; while the demoralized natives around the vacated camp kept up their frenzied rushing hither and thither, seeking aimlessly their hidden enemy, the four camels of the expedition, aroused by the unusual sounds prevailing, stalked slowly forward into the thick of the mêlée, and there they stood, their long necks swaying curiously, like fearsome spectres from an unknown world. A howl of terror burst from the group who had located the position of the defenders, they ceased their onward course, hesitated for a moment, then turned and fled precipitately, an example which the rest of their stricken brethren speedily thought fit to copy; and before Mackay or any of his companions could realize what had happened, the entire assembly were in full retreat, leaving the bulk of their spears and boomerangs littered on the sand.

"Good for you, Misery!" applauded Jack, running forward, and the leader of the team, hearing the well-known voice, staggered to meet him and knelt at his feet.

"I reckon we owes them animiles the price o' our carcases," said Never Never Dave, sententiously, as they walked quietly back to the deserted camp-fire. They found their blankets lying as they had left them, but transfixed with numberless spears, and after carefully extracting these crude yet deadly missiles they replenished the fire with them, and lay down to rest beside the ruddy glow, for it was now early morning, and the air had become unpleasantly chill. The corroborree beacon had been deserted, only occasional scattering sparks showing where the strange ceremonial had taken place, and away in the distance the vague crackling of branches indicated that the would-be annihilators of the camp were already far from reach.

"Great Centipedes! That was a close shave," growled Emu Bill, before he dropped off to sleep.

"But we have the advantage of knowing," returned Bob, with his usual calm philosophy, "that we shall find water near where the beggars held their odd orgy, and that should recompense for much." Then his eyes closed in slumber, and he entered a realm of phantasies where hostile aborigines and dreary salt plains were alike unknown. The weary strain of the night was over.

They found water after daybreak as they had anticipated. It was contained in a deep sunken rock-hole with an almost unfathomable bottom, wherein one might well fancy some dread monster to exist. They refilled the empty water-bags with thankful hearts, and, fearing another attack in force that night, renewed their march early in the afternoon. It was soon apparent that a better country had now been reached; dry it was certainly, yet the soil showed a considerable improvement over that already traversed, and the scrub became almost continuous instead of in sparse and far-divided belts as formerly. But though all promised well for an unusually favourable journey that day and for many days to come, the presence of hostile bands of aborigines all along the route of travel was too evident a feature of the landscape to be overlooked, and the team had perforce to move onwards warily.

"I do hope," said Mackay, as the evening approached, "that the blacks will give us a rest to-night. There's more risk in these scrimmages at close quarters than is healthy."

Bob had arrived at that conclusion some time before. "We're not more than fifty miles from the location you gave me of Bentley's last camp," he observed gravely. "If I shift the course slightly to the south to-morrow we ought to be up at it in three days."

A spasm of pain crossed Mackay's face. "Ay, my lad, we'll need to be extra cautious now," he said meaningly. "We mustna allow oursel's to be wiped out before we come to the mountain. I've got a bit of a score to settle in that quarter."

The sun was now but a few points above the western horizon, and his fiery radiance bathed the great silent bushland in golden splendour. The motionless mulga and mallee shrubs seemed ablaze with ruddy light, and the wastes of sand shone as a sea of burnished bronze. Not a sound was heard save the harsh cries of the gaily plumaged parrots that flitted eerily from tree to tree, and the occasional dismal monotone of the mopoke. Then suddenly from the shadow of a thicker clump of timber than usual a series of yells rang out, and at the same time a shower of spears whizzed overhead, and perilously close. Each member of the little group realized in an instant what had happened, and seized his rifle.

"Get the camels under cover, boys!" cried Mackay, from his position well ahead of the main party.

"There's nary bit o' cover!" roared back Emu Bill, who had diplomatically stretched himself flat on the ground at the first alarm. Whiz! splash! Even as he spoke a long quivering missile rushed through the shadeless branches and penetrated the great water-bag overlapping Remorse's flank. The stout canvas resisted the shock sufficiently to save the animal from injury, but the precious and dearly-hoarded contents gushed from the rent created in a copious flood. A cry of horror broke from Bob, Jack uttered a wail of anguish, and an expression of much fervour issued from Never Never Dave's mouth. With a bound Mackay rushed forward in vain attempt to save the few remaining drops, but it was not to be; before they had time to realize the seriousness of their loss the gurgling stream had ceased; the canvas skin had given up its store.

"I'll pulverize the hyena that did it!" howled the Shadow, dashing forward through the scrub.

"I'm with you," cried Jack, following closely at his heels.

It all happened so quickly that Mackay had no time to give any directions or restrain the indignant pair. Several further flights of spears skimmed well overhead, and one or two barbed darts more surely aimed, whistled dangerously near to Mackay's head.

"This is gettin' mighty monotonous," growled Emu Bill, looking around impotently, for as yet not a single savage was to be seen.

"There must be water in the district," said Bob, coolly, examining his revolver. "I suppose we've got to go on the hunt again." Without further remark he turned and rushed after his companions, whose vehement shouts as they charged along were mingled with the shrill cries of the dusky warriors. "Try and catch one, Shadow," he loudly shouted as he ran.

Fearful that disaster might overtake the entire party, Mackay gripped his rifle and hurried after them, leaving Emu Bill and Never Never Dave in charge of the team, a position which they condemned bitterly at such a time. The shadows of night were fast closing in, and between the trees of the pigmy forest a heavy gloom had settled providing excellent cover for the blacks should they have decided to renew the attack; but these strange creatures, having discharged their weapons, were now beating a retreat, yelling most hideously the while.

Scarcely fifty yards before him Mackay could dimly descry Jack, the Shadow, and Bob leaping on after the fugitives, and he quickened his pace in order to come up with them.

"We'll catch a specimen," cried Bob, eagerly, "if we have to chase them all night."

On they raced, while the crackling branches a little way ahead betokened the nearness of their quarry, whose shrieks alone would have been an unerring guide. Evidently the fleeing warriors were just as tired as their pursuers, for they were gradually losing ground. Suddenly one of their number screeched out some sort of signal which had the effect of making the runners scatter in all directions. Bob could just see their shaggy heads above the bushes as they diverged on various tacks; then the new order of things confused them all, and one by one the gorilla-like figures vanished from their view. Yet still they kept up the race, loth to return without some satisfaction. The night was rapidly darkening, obscuring the scrub and intervening sand wastes in a common pall, so that progress was made only with great difficulty, and wearily the aimless search was continued.

"We'll have to turn, boys," said Mackay, at length, when the stars commenced to glimmer in the heavens. "We must go back to the camels. To-morrow we'll have a look round for water. And to think that we had any amount of it this morning——"

A hearty exclamation from the Shadow interrupted him. They were passing under an unusually large lime tree, and that youthful individual had halted with an unrestrained roar of mingled merriment and relief. Looking up against the stars Mackay could see an awkward figure scrambling frantically among the higher branches.

"Treed! By Jove!" cried Bob, gazing upwards also.

"I reckoned I smelt nigger," said the Shadow, when he had recovered his equanimity; "but if his long legs hadn't banged me on the cocoa-nut, I'd never ha' thought o' lookin' in the tree for the skunk."

"And now comes the job o' gettin' him down," said Mackay. "An' it won't be an easy contract either, judgin' by the way he hangs on to the branches."

"The Shadow and I will soon attend to him," said Jack, with a laugh; and without further ado he commenced to swarm up the small round trunk of the tree.

"Be careful, Jack," warned Mackay. "He may smash your head before you reach him."

"Will he, though?" growled the active climber, already half-way up.

"Strategy's the word, Jack," councilled the Shadow, as he prepared to ascend to his companion's assistance. The lithe tree swayed under its load, then bent until its lower limbs reached the ground.

"We'd better see that our prisoner doesn't make his escape by jumping for it," remarked Bob, and he and Mackay therefore stood at opposite sides of the tree, watching the huddled form with alert eyes. Nearer and nearer Jack writhed his way to the top, and slowly the terrified aboriginal retreated to the farthest limit of the branch on which he rested, until it cracked ominously.

"I guess I've got you now," muttered Jack. "You just wait till I come to you."

But the shivering savage had no such intention; and as Jack approached he began to scream horribly, more after the manner of a wild beast than a human being. Then he broke off bits of the lesser branches and twigs, and showered them down on his implacable enemy.

"Just shake him off the branch an' I'll catch him," advised the Shadow, worming his sinewy form along the limb directly underneath his prey.

In vain Jack endeavoured to grasp his prospective prisoner, the oily native eluded him every time, and sorely tried the persistent besieger's temper by keeping up a vicious fusillade of wood fragments. He had, however, completely overlooked the presence of the Shadow directly below, and when in the midst of a furious assault, his foot slipped slightly, it was instantly seized by that watchful gentleman, and held in a ruthless grip.

"Now, I reckon you've got to come," said he, evading the free limb's onslaught with much dexterity. "Now! Stand from under, boys!"

Crash! They came down all three together, the top branch having broken with the strain, but the height was not very great, and the sand below was loosely packed.

"It's a jolly good thing," quoth the Shadow, "that the black beggar was so nice and soft; it was just like bouncing on top o' a cushion, it was."

Jack did not appear to be particularly grateful for anything as he picked himself up, but he very promptly took an arm of the captive along with the Shadow.

"Yes, that's right; take care of your prisoner now that you've got him," said Mackay, turning to lead the way back to the spot where the camel team had been left. "We'll have to mak' the most o' his knowledge."

Then he addressed the sullen aboriginal, and by a constant repetition of the word "Babba" (water), sought to make him understand their needs. But it was all to no purpose. The captive made no sign, and only groaned horribly when the question was pressed with a show of anger.

"All the same," sternly spoke Bob, "he'll have to tell us what he knows before morning."

In a short time they had reached the camels, where Emu Bill and Never Never Dave awaited them with ill-concealed impatience. But their joy on observing the aboriginal was great indeed.

"I reckon he'll get water for us all right," said Emu Bill, as they unloaded the camel. "I just reckon he will."

The Shadow now proceeded to build a fire, and soon the roaring flames leapt up cheerily. Having no water, they could not make tea, so they contented themselves with munching some pieces of damper, for which, however, they had little appetite.

It was at this point that the prisoner showed signs of interest in the proceedings, and Jack thereupon proffered him a substantial bunch of the dry fare, which he seized and ate with avidity.

But still Mackay's repeated interrogations seemed to have no effect on the savage, who kept glancing over to where the Shadow was gingerly slicing up some tinned conglomeration which is served out to explorers under a variety of names, and he opened his cavernous orifice expectantly.

"The poor beggar is hungry," said Bob. "Let him have a piece of that unknown substance, Shadow; if it does not kill him it may arouse some sense of gratitude."

"He'd reduce our stores mighty quick," grumbled the Shadow, noting with dismay how rapidly his hospitable offerings disappeared.

"Just hold on a jiff," murmured Emu Bill, thoughtfully. "I reckon I has struck a daisy idea." He hastened over to the many sacks lying on the ground where the camels had been unloaded, and came back with a handful of salt. "When you are as old as I is, Shad," said he, graciously, "you will know how to handle blacks, I calc'late. Does ye savvy?"

The Shadow took the salt with humble deference, and without a word proceeded to mix it lavishly with the contents of a small tin of the afore-mentioned compound, which he then handed to the hungry native.

"Eat every bit o' it, ye howlin' baboon," said he, kindly, "an' if ye isn't as thirsty as a camel after it, I reckon there must be something wrong wi' your construction."

Mackay and Bob listened to the schemers with amusement, then, as they saw the ravenous heathen bolt the salt-laden meat with great gusto, they forgot for a moment their own thirsty condition and indulged in a paroxysm of laughter.

"For a certainty our dusky friend will want water badly soon," said Bob; and they all sat around the camp fire and calmly awaited developments. If their prisoner knew of the presence of water in the vicinity he must surely endeavour to find it—half a pound of the strongest salt in his interior might enlighten him as to the meaning of 'Babba Babba,' which Mackay had repeated to him so persistently. And they were not mistaken. Half an hour later he began to show unmistakable signs of uneasiness, and his lips moved like the gills of a fish out of water. Then he strained at the rope which bound him to a mulga sapling behind, and rolled his eyes beseechingly.

"Better give him a full hour yet," said Mackay. "We can thirst just as comfortably as he can now, I think."

Emu Bill chuckled dryly.

"I is a grand instructor o' furrin' languages," he said. "I just reckon that that there nigger knows what water means now."

It was nearly midnight, and the slow minutes dragged like ages as they sat around the fire anxiously watching the antics of the salt-gorged aboriginal. For a long time no one spoke, but their basilisk-like glare evidently disconcerted the sufferer in no little degree, and he commenced to moan in an exceedingly melancholy manner, and endeavoured to evade their gaze by every artifice in his power.

"He thinks we mean to eat him, and have been feeding him to make him nice and plump!" hazarded Bob at length, and he had truly guessed the captive's thoughts. However, the tortures of thirst were surely having due effect on the poor savage, and his cries soon became most distracting to the listeners' ears. Suddenly he broke into a wailing chorus which echoed dismally through the still air, and caused even the long-suffering camels to raise their heads in protest.

"B-bab-ba-bab-ba!" he cried, tugging strenuously at the binding cords.

"Patience ain't so bad a virtue, after all," soliloquized Emu Bill, calmly slackening the rope from the tree, and gripping the free end of it tightly. With a bound the native headed out into the densest part of the scrub, almost pulling Bill over the sand in his frantic haste; the rest of the party followed at their best speed. Their now tractable guide did not lead them any distance. He stopped in a small hollow not far from the scene of his capture, and with feverish hands scraped away some covering twigs and branches, revealing to the onlookers' eager eyes a glittering pool of clearest water.

With a deep gurgle of relief he buried his tangled visage in the spring, and drank so deeply that the Shadow felt compelled to jerk him backwards out of sheer regard for his welfare.

"It's mighty stupid o' ye drinkin' so much after a heavy supper," said he, reprovingly. "It's real bad for your digestion, I reckon."

CHAPTER XIII The Mystic Mountain

"Latitude 27° 42´ 10´´, longitude 128° 7´ 11´´." It was noon three days after leaving Thirsty Spring, as their last strangely-found well had been designated, and Bob read aloud these observations as he noted them down in his log-book. They had reached the vicinity of Bentley's last camp, and all eyes had been alert for the melancholy symbols of the ill-fated expedition. Away to the east the country extended back in a series of rugged "blows" until they suddenly merged into apparent nothingness; a swelling, white haze obscured the true horizon in this direction, but north and south well-wooded grassy plains stretched into the dim distance. The uttermost edge of the desert seemed to have been reached at last.

"Ay, it was just about here that the camel broke away," said Mackay, musingly, "and over there"—he pointed to the east—"lies the mountain."

"It must be a terrible long way over there, Mac," commented Emu Bill, "for we should see it 'bout forty miles off if it is any size, an' you said it was a whopper."

Mackay looked puzzled; certainly no mountain was visible at this period.

"It must be there," he reiterated grimly.

Bob, too, was much exercised over the prolonged absence of the desert sentinel; it had figured so much in all their calculations that it had, indeed, been the initial quest of the expedition.

"There's an extraordinary heat haze rising up straight ahead," said he. "Perhaps it hides that shadowy mountain."

"It's there right enough," said Mackay, again. "I mind well that I didna see it until I was right up against it."

"There's something mighty uncanny about this place," grunted Never Never Dave, who had been gazing around suspiciously.

A gentle zephyr breeze wafted towards them from the obscuring mists, and they sniffed the air wonderingly.

"Blow me tight, boys," muttered Emu Bill, "we has struck old Jimmy Squarefoot's country."

"That are a fact," concurred Never Never Dave, solemnly; "we has come a bit too far on this trip. No wonder poor ole Bentley didn't get back."

"Why, what is wrong?" asked Jack, in some alarm.

"What is wrong?" echoed Never Never. "Why, we must be near Hades, my lad; don't you smell it?"

A strong odour of a pungent, sulphurous nature assuredly filled the air. Mackay was equally mystified with the others, though he did not give expression to his thoughts. He was trying to recall to the minutest incident the happenings of over a year ago in the same district.

"I distinctly saw their tracks," he repeated, half to himself, "and the bones——"

"But there ain't no bones now," interrupted Emu Bill. "There's some curious mystery about this here place, there is."

A cry from the Shadow, who had gone exploring on his own account some distance off, drew their attention. It was plain that he had discovered something important, for he semaphored to them excitedly as they looked. Silently they obeyed his summons, and in a few minutes were gazing at the poor relics of the last expedition, where they lay half covered in the sand.

There they were beyond a doubt, a mass of bleaching bones. Reverently they uncovered their heads, then Mackay knelt down by the sad litter, and great, dry sobs shook his breast. His companions turned away with heavy eyes, all but Bob, who remained to comfort the grief-stricken man.

"We may at least bury the remains," he said sadly, "and I think we might put up a small mark over the spot. There are lots of trees about which we could cut down."

Mackay looked at him kindly. "Not yet, Bob, not yet," he muttered hoarsely; "not till I have squared accounts with the wretches who committed this crime. These poor fellows here were murdered after daring the dangers o' the desert; their last mortal remains have awaited my coming here on the surface o' the sweltering sands, and they cry to me for vengeance—and vengeance they shall have before I cover them from the light o' a just Heaven." He rose with forced calm and linked his arm in Bob's. "You shall help me, Bob," he said earnestly; "you of all people have a reason——"

He ceased abruptly as Emu Bill appeared once more. The tall bushman was apparently much moved, though he strove to hide his sorrow.

"I has just been talkin' to Never Never," he began, in an even voice, "an' we has come to the conclusion that we'll go an' wipe out some o' them skunks who did this. I reckon we'll feel better after it."

Mackay smiled faintly. "I believe we are near the end o' our search for the hidden treasure o' the Never Never," he said quietly. "The invisible mountain must mark the entrance to the land we are seeking, but we may have many a struggle before we triumph, but each difficulty overcome will bring us nearer our goal. Let us move on once more, Bill; I must see the other side o' the mountain——"

"An' nary one o' us is goin' back on you," said Emu Bill, with a grim laugh. "Wherever that there perfume comes from, I reckon Never Never an' me will see the end o' the journey."

They retraced their way to the camels, and in a short time were forcing a trail on into the seething mists. And now the stumbling camel-train experienced great difficulty in negotiating the many dry ravines that lay in their course, and they climbed over the basaltic bluffs which now and again reared their heads above the boulder-strewn expanse, only with the extremest effort. The sun beat down pitilessly on the wayfarers, and here the heat was, indeed, overpowering; it seemed to rise in long, pulsating swells from the bare rocks and hang in a filmy cloud of vapour, through which the eye could see but vaguely, as in a dream-picture. On, on, the pioneers struggled, and as they proceeded, the strange, sulphurous odour became more and more perceptible, until it assailed the nostrils in sharp, burning breaths. Yet still the vision ahead was clouded by dense white vapours, and the horizon remained obscured. Then suddenly a curious thing happened: the shrouding curtain in the near distance lifted up like a giant screen in a theatre, and through the mists of dispelling ether a dark towering height loomed up vividly.

"The mountain! the mountain!" cried Jack; and truly it was a mountain, and a mountain of so precipitous and forbidding an aspect that it looked like an immense black wall rising into the sky.

"That is just how I ran up against it before," said Mackay, calmly. "It appeared all at once, and I wondered why I didna see it earlier."

"Well, this beats me," growled Emu Bill. "An' why in all the world didn't we see such a colossal monument before? We oughter have sighted that there tower o' Babel at least two days back."

Even as he spoke a great white mask rose from the base of the towering elevation, and in an instant the mighty landmark had vanished from their view.

"I reckon we has had a sight o' ole Jimmy Squarefoot's furnace," remarked Never Never Dave, mysteriously. "An' don't it smell strong?"

"It jest howls," groaned Emu Bill, gasping hard.

Mackay kept an unmoved silence. He apparently had no intention of being surprised at anything; but Bob somewhat eased the minds of the twain by endeavouring to explain the phenomenon they had witnessed.

"The covering haze is nothing but steam," said he. "I think the mountain must be volcanic."

Mackay shook his head. "I shouldna wonder if it is an extinct volcano," he said; "but there was no lava flow that I remember, and it disappeared just the same."

Notwithstanding the odd happenings during the last few minutes, the camels were not permitted to slacken their pace. Each and all of the party had determined to probe the mystery to the fullest, and the solution was soon forthcoming. As they forced their way into the densest depths of the ghost-like curtain, they became quickly aware of a gurgling, boiling sound almost at their feet. Bob's keen ears were the first to catch the unwonted echoes; but before he could speak a greenish-yellow cloud rolled before his eyes, and he staggered back, choking wildly.

"Ease off, boys," spoke Mackay. "We must scout around an' investigate before we go further."

The whole party, camels and all, were now enveloped in the wreathing smoke-columns, and the sky was hidden from sight. Blindly Bob made a few steps forward, keeping well to the right of the unseen caldron, which now bubbled and foamed spasmodically. The Shadow followed, stumbling and gasping, and within a minute the two found themselves in a clear and untainted atmosphere, and but a yard or so from the base of the gloomy mountain. Loudly they shouted to their companions, and soon the spectral forms of the camels hove into view, with Mackay and Jack treading cautiously at their head. But where were Emu Bill and Never Never Dave? They seemed to have vanished completely.

"They were alongside Jack an' me a minute ago," said Mackay, gazing wonderingly around.

"I reckon I'll go back an' see if they've stopped to look at the scenery," grunted the Shadow; and he made a dash into the heavy fumes once more.

The three who waited by the camels heard a startled cry, followed by a faint splash, then all was silent. Hastily Mackay seized a camel pack-rope, and would have rushed off after him, but Bob interfered.

"I think I can guess where to find them," he said. "Let me go."

With reluctance Mackay saw him depart; but before Bob had entered the chaos the swelling mass rose before him, disclosing in his track a broad, pit-like cavity. Hurriedly he strode to the edge of the caldron; but ere he reached it the Shadow climbed out of its seething depths wet and dripping, and saying strange things to himself. Immediately behind him Never Never Dave's head popped up, and an eloquent flow of language was let loose upon the air. Lastly, Emu Bill scrambled into the open. He looked savagely around for a moment, until he caught sight of the Shadow, and his wrath overflowed in a torrent of abuse. All three were bedraggled enough looking specimens; but the last arrivals were considerably worse off than the Shadow in that respect—their hair was covered with a greenish scum, which spread down over their faces and almost blinded them.

"It was all that wretched young Shadow's fault!" roared Emu Bill.

"But you were there first, Bill," remonstrated Mackay, laughingly.

"Of course we were. We went plump into the filthy boilers; but we got a good grip o' the sides, and were sliding out quick an' lively, when, blow me! if that howlin' scarecrow didn't bounce down on top o' us, an' sent us swimmin' like tadpoles to the bottom. Ugh!"

But their indignation quelled speedily when they learnt how excellent had been the intentions of the much-maligned youth.

"It must be a hot spring," said Bob.

"And there are more of them," cried Jack. "See, they are scattered all round the foot of the mountain."

"I reckon it is hot, right enough," grumbled Emu Bill. "I'm just 'bout turned into a Salamander, I is."

As Jack had noticed, quite a number of similar indentations formed a line right along the base of the mountain, and in each yawning crater examined, a greenish-yellow fluid bubbled tempestuously. High overhead the smoke-wreaths dissembled into thin air, and for a brief space all was beautifully clear. Then a dull rumble like the mutterings of subdued thunder was heard, and immediately snowy puffs of smoke issued from the strange cavities. The denser fumes rapidly spread along the ground like a turbulent, foaming sea; then the whole seemed gradually to rise upwards and suspend as a filmy pall before the face of the mountain. Yet, strangely enough, the noxious odours were now almost absent.

"Ay, it's vera marvellous," said Mackay, with a sigh. "So does Nature protect her treasure-houses."

"It's a wonder you managed to get through without accident when you came," Bob observed thoughtfully. "But, then, it's possible the line was clear when you passed."

"A breeze of wind would have lifted that fog," hazarded Jack. "I should think that on some days the clouds would not be nearly so constant nor so thick."

"You're possibly right, Jack," mused Mackay, looking upwards. "See how the smoke curls in to the west now."

They all followed his gaze, and, surely enough, the mists appeared to bend over before a powerful air current and break off into numberless flying patches of lambent spray. Assuredly, a fairly strong blast must be blowing on the mountain summit, though all was serene and unmoved below. They now bethought themselves of having an inspection of the wonderful elevation, which they had reached after so much weary striving. There it stood, gaunt and bare, precipitous in outline, and rising almost sheer to a height of over eight hundred feet, and as far as the eye could reach in either direction along the base, the same grim barrier appeared, but it curved in almost imperceptibly at each limit of observation.

"The monument might stretch across into Queensland," said Emu Bill, "if we tried to follow it round. I vote we does a scramble over the top."

"I tried that before, Bill," answered Mackay, "but I'm going to try it again. Only we'll look for the easiest side before we start."

"But what about the camels?" asked Jack. "We can never get them over it."

"An' we've got to remember that there's an all-fired quantity o' bloodthirsty niggers about," said Never Never Dave.

"Suppose we hobble them out on the other side of the smoke," suggested Bob. "If the blacks stay beyond the mountain they couldn't very well see them so close in, and the camels are too tired to wander much."

"It's a risk, Bob," said Mackay; "but the whole journey has been a risk, an' it's the best we can do. We can keep an eye on them from the top—if we get there."

"An' our rifles can speak for us from there well enough," laughed Emu Bill; "an' there's one howlin' satisfaction about it, there's nary spear could reach us."

And so it was arranged; the four tired beasts were unloaded, the bell was unstrapped from Misery's neck, and the Shadow led them out to the plains, manœuvring most carefully in his passage between the bubbling caldrons. In a few minutes he returned, with a somewhat anxious visage.

"I is pretty certain I saw a nig on the top o' the hill when I was out back a bit," he announced.

"On the top o' the hill?" cried Emu Bill, incredulously. "Well, if they don't pop too many spears at us, I don't mind if they stay there until we get up."

"But you couldn't see anything through the haze, Shad," said Bob.

"I just did. The top o' the concern was shining strong in the sun, an' I got a sight o' a big nigger dressed like a corroborree mourner standin' looking' at me."

It was quite possible that the Shadow's information was correct, for the fine haze in the upper air would barely have obscured the bold ridge of the mountain summit, especially with the sun's rays beating strong upon it. Yet it was evident that the young bushman's statement was received with considerable unbelief.

"It's been a hallucination, Shad," laughed Jack.

It was already late in the afternoon, and it would have been useless to attempt the climb that night, so a tour of investigation was made in order to discover the least impregnable aspect of the frowning barrier, and as the little party moved along they carried their rifles ready for immediate action in case of a sudden alarm. But not a sign of natives was observed, and they tramped mile after mile over the jagged rocky débris lining the base of the mountain without once noting an easier place of ascent than that which they had first gazed upon. Not a trace of vegetation showed on the steep declivity; the bare rocks scintillated in the last rays of the setting sun, and showed up barren and forbidding. Here and there deep clefts appeared, striating the gloomy formation, and cutting deep into the heart of the mountain. It was one of these that drew an exclamation from Mackay.

"That looks vera like the cap o' a gold-bearing lode showing at the bottom o' the gully," he cried. He crept carefully into the yawning crevice, and broke off a piece of the supposed auriferous stone with the iron heel of his boot. "Decomposed diorite," he announced, "and showing gold all over. I do believe the whole mountain is just a mass of gold lodes an' leaders."

"Well, I'm blest," murmured Emu Bill, "if that don't beat everything——"

"But we can't carry the hillock away," said Jack, hurriedly.

The difficulties of transport had at once appeared to his practical mind, and his words acted as a restraining tonic on the exhilarating spirits of the others.

"You're right there, Jack," agreed Mackay, with a smile, "but if we get plenty of water on the other side, we could very soon get machinery out here; an' I've a firm idea that our golden land o' promise lies just beyond this barrier." He tapped the rocky surface with his hand meditatively. "And more than that," he continued, with rising excitement, "I believe we'll find rubies and diamonds as well. I mind we picked up some rubies in the gullies around the last camp when I was here before. At least, Phil, the geologist, said they were rubies, an' I'd back his knowledge in that direction against any man's. He said they had been shed from some mountain or other, but, of course, we hadna seen the mountain at this time; and poor Phil never did see it, either."

They commenced to retrace their steps, for the night was fast closing in, and as they walked along, Bob stooped down occasionally to pick up pebbles from the silted driftage at his feet, and unobtrusively placed them in his pocket for future inspection. They had almost reached the place where they had unloaded the camels, when the Shadow shouted out triumphantly—

"Look, boys! I reckon there ain't no mistake about that nigger, is there?"

He was gazing at the ridge forming the summit of the mountain, and looking up, Bob saw a tall, dishevelled figure standing against the sky-line and waving his arms energetically.

"By gum, he is wild!" laughed Emu Bill; "an' what a dandy outfit he's got; why, the beggar's got a 'possum blanket over him."

He raised his rifle mechanically, but Mackay had already levelled his piece at the silhouetted form.

"Please don't shoot," pleaded Bob, staying his hand. "It almost seems like murder to kill a man like that."

Mackay lowered his weapon with a groan, and Bob, looking upwards once more, was astounded to see the object of his commiseration extending his hands as if in benediction. He stood thus for a moment, then, with a despairing gesture, pointed towards the Western desert.

"I'm glad I didna shoot," said Mackay; "that's the most wonderful savage I've seen. He even tried to warn us not to come further."

"That was out o' gratitood for us not shootin'," laughed Emu Bill; "but, blow me, I can't shoot a nig when he hasn't a spear or weapon o' some sort in his hand."

When they looked again, the strange aboriginal was gone.

The spirits of the little party were unusually cheerful that night, as they sat around their camp-fire and talked eagerly over their prospects on the morrow. Their objective had been reached at last, the toil and stress of the dreary journey was over, the reward—and of reward they all seemed well assured—was now about to be theirs.

"I reckon I'll give ye a hymn o' praise on the orchestra," remarked the Shadow, pulling his ear-shattering instrument from the pocket where it had lain silent since the finding of Fortunate Spring.

"If ye does," threatened Emu Bill, "I'll dump ye in that there smelling solution right over the head."

"Hang it, Bill," complained the unappreciated musician, "I ain't quite dry yet, as it is. Couldn't ye think o' some happier kind o' return for my professional services?"

"Anyhow," consoled Jack, "it wouldn't do to let the niggers know we were about; they might come for us when we were helplessly enslaved with your melody."

The Shadow grinned. "Right O," said he; "music is off."

But Mackay had not seemed at all unwilling to encourage the youth's suggestion.

"The blacks should ken we are about by this time," he observed lightly; "but there are six good rifles in this camp, an' we might as well encourage them to come out now as at any other time. There's going to be a good moon up to-night."

"You might give us a tootle on the flute," said Never Never Dave; "I hasn't heard ye play since we left Golden Flat."

"Let us have 'The Muskittie's Lament,'" urged the Shadow; "I is just dyin' to stretch my voice a bit."

"No, Shadow; though you are a budding Sims Reeves, I can't sympathize wi' you enough just now to listen to you singing. I must even deny you the pleasure o' hearing me warble the old familiar tune to-night, for I'm no' in the mood for waxing extravagantly joyous. But seein' we've reached the deceivin' mountain at last, and without mishap, I'll gie ye a blaw on the flute, if only to make this night something different from other nights."

Jack fetched the flute with alacrity, and then seated himself beside Bob, and soon the little group were listening in hushed silence to the pensive strains of one of Balfe's melodies. When it was finished, the man of many moods paused for a moment, and his eyes roamed instinctively back towards the desert, and though the smoky cloud still intervened, Bob guessed at once that he was again filled with swelling memories of the past.

"Let us have something lively, Mac," said Emu Bill, "something that will make us forget them pestiferous niggers for a bit."

"I can't do it, Bill," came the husky response; "not here, not to-night." Then he lifted the flute once more. "I'll play you one o' Bentley's favourite hymns," he said gravely. "Well do I mind we used a' to sing it whiles when we were on the march."

Softly into the night rose the notes; they lingered by each deep crevasse on the mountain side, and echoed back from the rocky steeps. Unspeakably entrancing was the effect. The musician himself seemed lost in the wonderful sounds he created, and his hearers, after listening in mute attention for some time, by a common impulse joined in with the words, familiar to them all—