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[Pg 305] 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[Pg 306] 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.

[Pg 307]

"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[Pg 308] 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[Pg 309] 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.

[Pg 310]

"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[Pg 311] 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,[Pg 312] 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[Pg 313] 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.

[Pg 314]

"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,[Pg 315] 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[Pg 316] 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."

[Pg 317]

"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[Pg 318] 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."

[Pg 319]

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[Pg 320] 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.

[Pg 321]

"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[Pg 322] 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[Pg 323] 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 att............