Perhaps, he thought, they were part of some building still more ancient than the fort itself. It would be interesting to excavate more thoroughly, and find out whether anything of value, in the shape of old weapons, coins, or pottery, lay beneath the foundations.

But that must be a task for the future. At present the business in hand was the completion of the ditch. The bricks being almost level with the bottom of the part which had already been dug out, he decided that it was unnecessary to remove them, and he ordered the men to go on with their work in another direction.

By dusk that evening the ditch was half finished. Royce, after eating his scanty supper, was sitting alone, tired out, wondering what had happened to Challis, whether he would succeed in getting help, how long it would be before he came back.

All at once he heard a shout of alarm, followed by a cry of pain. Springing up, he rushed in the direction of the sounds. The whole garrison was in a ferment, and two of the men had reached the scene before him.

"What is it?" he cried, thinking that perhaps some of the men had been quarrelling.

But on his arrival he found one of the Hausas groaning with pain, supported by his two comrades. They pointed to a gash in the man's thigh.

"Bring him along," said Royce to Kulana, deferring questions until he had rendered first-aid.

They carried the man to Royce's room. Royce took some lint from his medical stores, soaked it in water, and tied it tightly over the wound. He saw at once that the injury was not serious, and the cut, being clean, would heal in a few days.

"Now, how did it happen?" he asked.

The negro told Kulana that he had suddenly seen beside him a stranger, a man of immense size, very fierce-looking, with two long scars on each cheek. He had given a shout of alarm and rushed at the man, who was moving stealthily towards the well-yard. At the shout the stranger turned, dug his knife savagely into the Hausa's side, and rushed away.

Royce wished that he had questioned the man before. It would be hopeless to search for the intruder now. From the description, he had no doubt that it was Goruba, who had entered the fort for the second time in some mysterious way.

Royce was staggered. How had the man contrived again to get in unperceived? What sentries could cope with him? What could be his object in coming alone into the fort? Why was he running such risks in venturing unsupported among a garrison whom he knew to be well-armed and watchful?

"I must solve this mystery," Royce said to himself. "The men are scared out of their wits, and if this sort of thing is to happen their courage will melt away. There must be a secret entrance somewhere. To-morrow I'll search the place thoroughly again, though, upon my word, we have been through it so often that I can't for the life of me conceive where the rat's hole can be."

He gave the wounded man a sleeping-draught, did his best to calm the fears of the rest, and remained on guard all night, in case another alarm should create a panic.

CHAPTER XXI

A BLOW FOR LIBERTY

Challis grudged every day spent in training, lest the fort should be stormed by the Tubus before he had come to the relief. But he saw clearly that only by training his little army would he have the slightest chance of effecting a diversion in favour of the beleaguered garrison.

The odds, in any case, were enormously against him. But at the end of the fifth day he had unexpected encouragement. About nightfall, just as John was lighting the bonfires, he caught sight of a crowd of armed negroes rounding a hillock some distance away.

"Bad fellas coming, sah!" he shouted excitedly.

Challis blew a whistle he had shaped out of a piece of wood, and his eighty men came pouring out of the cave, and formed up in something resembling the line which he had been at such pains to teach.

They howled with disappointment at not receiving the order to attack at once. Challis got the chief to send one of his men forward to hail the strangers and ask the meaning of their coming.

It turned out that they were the fighting men of a village about ten miles off, nearly a hundred strong. The story of the killing of the lions had reached them, with the addition of all sorts of wonderful details gathered in its course through the countryside. They had heard rumours also of the marvellous medicine which the white man was preparing for the Tubus, and they desired to see these marvels for themselves.

Their chief and the elders of the village had desired to take the cautious part and remain aloof; but their counsels had been overborne by the younger men, who had insisted on marching out to see the white lion-killer and medicine man.

It was an opportunity too good to let slip. In the ruddy light of the bonfires, Challis put his men through their evolutions.

Spurred by the desire to impress the strangers, the men excelled themselves. The result was that the newcomers clamoured to be allowed to join the forces of the great medicine man, and Challis found himself stronger by nearly a hundred vigorous, able-bodied young men.

The only drawback to this accession of strength was the necessity of devoting more days to training. Challis was so anxious about the welfare of Royce and his little party that he sent a scout next day to approach the neighbourhood of the fort and discover whether the Tubus were still in position there.

He set to work at once with the new men, selecting forty to join his spearmen and making pikemen of the rest. These latter he posted as a rear rank three feet behind the front rank, giving them spears three feet longer.

The new men picked up the simple drill quickly, having models in the original company. But before Challis had time to perfect them, his work was put to a sudden test.

In the intervals of training his men, he had made a point of studying the surrounding country with an eye to its suitability for attacking or defensive operations.

The cave was situated in a hilly, rocky district, difficult for horsemen, but well adapted for defence against a mounted force. The side from which it could be most easily rushed was from the direction of the nullah which had been the scene of his adventure with the lions.

A little below the spot at which this incident had taken place the nullah disappeared. The stream which flowed through it in the rainy season ran in a broad shallow channel, easily fordable, with a rocky hill on one side and a practicable path along the dry margin of the bed of the stream.

About two miles from the cave the rocky ground on the right of the stream ended in a swamp, formed by overflowings of a little river which Challis had satisfied himself was identical with the stream that flowed past the base of the hillock on which the fort stood. Into this river the shallow stream emptied itself.

On the right, at the angle formed by the junction of the two streams, there was a low-lying patch of dry land, triangular in shape—an island inclosed by streams and the swamp. While this island was at the present time dry, Challis had no doubt that it was submerged when the streams were flooded by the rains.

Challis had considered the possibility of being attacked before he was ready to move out towards the fort with his little army. He decided that such an attack, if it occurred, would most likely be made from this direction, the ground being more level and open than on any other side. It was clear that the best point at which to meet the attack would be where the swamp approached most closely to the steep hill on the left.

Including the shallow bed of the stream, about fifty feet wide, there were altogether about a hundred and fifty feet of firm dry land between the swamp and the hillside, except for the stream, now little more than a yard across. Here his men could best make their stand.

Since his arrival at the cave, Challis had insisted on an elementary precaution which it is the habit of negroes to neglect. Every morning at dawn he had sent out scouts in a southward direction, to give notice if the enemy approached. These men took sufficient food for the day, and returned at nightfall.

He arranged that the line of scouts should extend for several miles towards the enemy's country, each man posting himself within hailing distance of the next. By this means he ensured that he should receive warning within a few seconds of the sighting of the enemy by the remotest man.

On the sixth day after his arrival he had reason to be glad of his forethought. About noon the nearest scout ran in with the news that a force of Tubus was approaching from the direction of the river.

A fact that somewhat surprised him was that their line of march would bring them direct to the cave, not to the village whence the people had migrated. It seemed as if they had information of what was going on. Was it possible that there was a traitor in the camp?

With a little more experience of negro life he would have divined the true explanation. The story of his doings had spread for many miles around, gaining in magnitude with every repetition. Certain of the neighbouring tribes purchased immunity from attack by spying for the Tubus, and there was no doubt that some of these people had carried to Goruba the report that a white man was making big medicine at the cave.

But it was not at all likely that Goruba had any idea who the white man was, unless he had already stormed the fort and discovered that it contained one white man instead of two. The probability was that he was coming or had sent to test the truth of the story he had heard. The white man might be a missionary, unlikely to trouble him.

Challis, it must be confessed, felt very nervous. His men were as yet only partially trained; how would they behave if it came to a fight? Would they forget all that he had tried to teach them, and either run away from their dreaded enemy, or rush forward in their old disorderly manner, and fall an easy prey? He looked forward to the test with doubt and misgiving.

But he let no sign of his thoughts escape him. Within three minutes of the scout's arrival he had all his warriors ranged in double line.

"John," he said, "you will bring them along and down the hill after me. Be sure you do not let them break the line."

Then, jumping on his horse, he cantered along the bed of the nullah to the point where he had already determined to make his stand. One of the scouts ran beside him. On reaching the spot, he left his horse with the scout and climbed the hill on the left to get a view of the enemy.

It was some time before he was able to distinguish them. When he first caught sight of them they were picking their way very slowly and cautiously along the bank of the river. They numbered, as nearly as he could guess, about three hundred men—a force which, mounted, armed with rifles, and used to warfare, represented terrible odds against fewer than two hundred raw levies, on foot, and without firearms.

Small though their numbers were, however, and in spite of their imperfect training, Challis had no reason to be dissatisfied with the spirit of his men. Before he regained the bottom of the hill the whole of his force were already on the spot, so closely and eagerly had they followed in his footsteps. Their ranks were in better order than he had expected, and he praised them warmly, hoping fervently that their morale would stand the shock of the imminent conflict.

Losing no time, he drew them up in order of battle. With the swamp on his right and the hill on his left, there was no necessity to protect his flanks. Across the space between hill and swamp he placed a hundred of his pikemen in two ranks of fifty each. He had still twenty pikemen—these he posted in reserve ten yards behind the rear rank, to deal with any horsemen who might break through. Of these John was placed in charge.

Of the sixty spearmen, who had six spears apiece, he arranged that thirty should advance in front of the line of pikes, cast their spears, and run back within the lines for shelter. The other thirty he posted in the bushes fringing the hillside, with orders to remain hidden until the leading ranks of the enemy had passed, and then to assail the rear ranks with a fierce shower of spears.

And then, having placed his horse behind a tall bush, he stood, rifle in hand, tense with anxiety, in the centre of the front rank of his expectant men.

If at that moment he could have been spirited away to England, he would have been glad. He had no liking for the soldier's trade, but here he was, here he must stand; if there was to be a fight, it was for liberty and peace.

The enemy advanced slowly down the bed of the stream. Not until their front ranks turned the corner of the hill did they become aware that opposition awaited them. They then saw a line of men drawn across the bed of the nullah on their right, with a white man in the centre.

They drew rein for a moment to take stock of the little force opposed to them. Realising how small it was, they burst into mocking shouts and charged. Challis had hoped for nothing better, knowing that spears were no match for firearms.

He blew his whistle. Fifty more pikemen trooped out from the bushes on the right, and formed a second line behind the first; twenty ranged themselves in a third line. Then, before the jeering horsemen had covered half the distance between the two forces, they saw themselves confronted by a triple line of bristling pikes, a kind of obstacle to which they were unaccustomed.

But they did not check their charge. Galloping on with furious shouts, they were within a hundred yards of the pikemen when a flight of spears from their left hurtled among their ranks. Carried on by their impetus, the horsemen dashed upon the pikes outstretched across their front. In some cases the riders, in others the unfortunate horses, were the victims.

Some penetrated the first line and the second, only to find still a third awaiting them. Meanwhile their comrades in the rear had been assailed by another shower of spears, and, led by Challis, the pikemen whose weapons had not been broken by the charge pressed forward on the now wavering ranks.

Then the thirty spearmen on the hill came into action, darting out upon the rear of the Tubus, hurling their spears, and following up with a charge. Assailed in front, flank, and rear, the Tubus lost heart, pulled their horses round, and galloped away in the only open direction, towards the stream.

Crowding one upon another in their haste, many of them urged their horses on to the swamp, unaware of its treacherous surface until the animals began to sink. Then the men sprang from the saddles in fright, abandoned horses, arms, food, and rushed headlong away, to escape the spears of their pursuers.

It was just at the moment when the flight began that the victors temporarily lost their leader. As one of the Tubus was wheeling his horse, he dealt a sweeping cut with his scimitar at the pikeman standing next to Challis in the line. Challis threw up his rifle and intercepted the blow, which drove a deep dent into the barrel. The force of the impact caused him to stagger against the horse's flank; he was thrown to the ground, and the horse, galloping off, dealt him a kick with one of its hind hoofs. His pith helmet was flattened on his head. It saved his life, but he lay stunned where he fell.

When he came to himself, he found John bending over him, with a score of the negroes in a silent, anxious group behind.

"Where are they?" were his first words.

The negroes shouted with joy when they saw that the man who had taught them "medicine" was still alive. John pointed to the swamp.

"Ober dere, sah," he said. "Bad fellas all gone smash."

Challis raised himself on his elbow. He saw struggling horses, dismounted Tubus, some fleeing over strips of firm ground, others plunging deeper into the morass, with the victorious negroes swarming around them.

"Enough!" cried Challis, anxious to avoid slaughter now that his object was achieved.

He blew a shrill blast on his whistle. Most of the men turned and came hastening towards him.

"Bring off the rest, John," he said. "They are not to fight any more. Get ropes and save the wretches who are sinking in the bog."

The fighting ceased. Some of the negroes took ropes, hurled them towards the struggling Tubus, and hauled them to dry land. The prisoners expected to be butchered, the rescuers to be ordered to slay them. Both were equally surprised when John, at Challis's command, shouted that the Tubus were to be spared. The negroes could not understand why mercy should be shown to a merciless enemy, but Challis saw gladly that they obeyed him.

"Take them near the cave, and set a guard over them," he said. "We will teach them another sort of medicine."

Rising painfully, he surveyed the field. Some sixty Tubus would hunt no more slaves, burn no more villages. Many horses had been captured, together with swords, firearms of various kinds, and ammunition. The victory had been won at small cost.

Challis ordered that the wounded Tubus should be treated exactly like those of his own force. Then, feeling sick and dizzy, but proud of his men, and rejoicing in the success of his first blow for liberty, he went back to the cave, amid lusty shouts from the warriors and shrill cries from the women and children.

CHAPTER XXII

THE DISCOVERY OF RABEH'S HOARD

Royce spent several hours of the night of his discovery of Goruba's second entry in cudgelling his brains over his new problem.

Twice had Goruba made his way into the fort; twice had he escaped. Yet on neither occasion had anyone seen him on the ramparts, nor had anyone seen him in the interior except Challis and the man who had now been wounded.

What puzzled Royce almost as much as the secret of Goruba's means of entry and of exit was the fact that he seemed to make no use of it. Being able to get in and out without being observed, why did he not make use of his power, and lead his followers into the fort?

"I wish Tom were here!" thought Royce. "I feel like Robinson Crusoe before he had Friday to talk to. John is the only Hausa at all equal to Friday. I almost wish they had not gone."

Next morning he set the men again to work on the ditch, and went through the fort from corner to corner, searching for some secret passage. The gaps in the walls had all been filled up. The stone slabs of the floor all seemed to be solid; none of them gave forth a hollow sound when he stamped on them. At the bottom of the well the spring bubbled constantly, the overflow passing away through a narrow slit through which a rabbit could hardly have crawled.

"It beats me altogether," he said to himself after his thorough survey.

He walked round inside the wall to see how the men were getting on with the ditch, and came to the foot or two of brickwork which had been uncovered.

"I wonder!" he exclaimed, as a sudden thought struck him. "Gambaru, fetch me the spade."

When the man returned, Royce began to dig away the earth on each side of the brickwork, which was itself too hard and to firmly imbedded to be cut into or prised up by the only tools he possessed.

He found, after some little time, that the brick-work was about four feet wide and very deep, and that it extended inwards. Dropping the spade, he walked into the fort in the same straight line as the brickwork.

"This may be the clue," he thought with some excitement. "At any rate, I must see."

The direction of his walk led him straight to the well.

"A false scent," he said to himself, more puzzled than ever.

He went back to the ditch, to make sure that he had not been mistaken in his course. No; there was no doubt, about it; he felt sure that if he uncovered the brickwork completely it would end at or near the wall of the well.

Just as he was beginning to dig again, another idea occurred to him.

"It would take me a couple of hours to clear all the earth away," he thought. "Perhaps it would be waste labour. I'll have another look at the well."

He returned, Gambaru following, much puzzled at his master's strange proceedings.

Standing on the brink, he peered down into the well, which was wide and fairly light. He had seen nothing extraordinary about it when he supervised the clearing out of the rubbish; there was nothing extraordinary about it now.

In the walls there were rusty iron staples, intended as footholds, and so used by the men. He descended, examining the walls and the staples; there was nothing strange about them.

"The brickwork is just about six feet below the surface," he thought. "I'll measure the same distance here."

At a little more than his own height below the ground he scrutinised the masonry carefully. There were slight clefts where the separate stones met, but nothing unusual in their appearance. He pushed and strained at the stonework, without effect.

Then he noticed, just within arm's reach to his right, a staple quite out of line with the rest. It seemed to have been fixed in the wall without purpose. Leaning over, he pulled at it, at first cautiously, then more and more vigorously.

Suddenly he felt a shock of surprise. Was the staple moving, or was he himself? He planted his foot firmly on the staple on which he was standing, and still pulled. There was no doubt about it; he was slowly swinging round. The huge slab of stone against which he was supporting himself had moved inwards on his right, outwards on his left, and he was turning with it.

Now thoroughly excited, he tugged steadily, and in a few moments found himself looking into a dark aperture in the wall.

"Eureka!" he exclaimed joyfully, and Gambaru, leaning over the brink of the well above, gasped with terrified amazement as he saw his master disappearing.

"A candle!" shouted Royce.

The Hausa sprinted away, and returned with the whole garrison at his heels.

"Back to your places, you idiots!" cried Royce. "Kulana, keep them at their posts. Give me the candle, Gambaru."

Holding the lighted candle, he stepped from the staple into a low dark passage, and groped his way stoopingly along it. For some forty or fifty yards it was narrow; then all at once it opened into a huge natural cavern, warm and stuffy, with an earthy smell.

Royce looked about him and gasped with astonishment. The candlelight fell on an enormous store of elephants' tusks, huge and massive objects ranged in close-packed rows, and filling nearly three parts of the cavern.

"My word! What a find!" Royce exclaimed.

He began to count the tusks, came to a hundred, and gave it up.

"Five hundred, at a guess," he thought. "They must be worth a fortune. No wonder Mr. Goruba wanted to strangle me! ... What's that yonder?"

He went farther into the cavern. Beyond the tusks lay an assortment of many things—ivory cups, vessels of gold, an old French musket, swords, scimitars, a kepi or two, a French officer's sash, some cartridge cases, several native spades and pickaxes—and, at the far end, objects which caused him to recoil. They were human skeletons.

At this gruesome sight Royce felt that he had had enough for the moment. The air was stifling, rendered still worse by the smoky candle. He retraced his steps, stood firmly on the staple in the slab, and this time pushing at the other staple, caused the stone to revolve on its pivot and set flush with the wall.

"What does it all mean?" he thought, as he sat in his room above, eating the frugal dinner which Kulana brought him.

He remembered what the old chief had told him about Goruba—that he had been lieutenant of Rabeh, the extraordinary negro who had risen from the position of a slave to the lordship of a great territory in the Sahara, tyrannised over the natives, and long defied the efforts of the French to put him down.

Was this secret hoard of wealth Rabeh's? Had he stored it in this cavern in the side of the hill, hoping some day, when he had defeated the French, to dispose of it?

"That must be the explanation," Royce concluded. "I don't know anything about the ivory trade, but those tusks must be of immense value, and must have represented a vast fortune even to a potentate like Rabeh. I suppose he let Goruba into the secret. When he was killed and his empire broken up, Goruba was for years a fugitive, the old man said. But he was ambitious, like his master. He always meant to get hold of this treasure. What Rabeh had done, he thought he could do. No doubt he joined the Tubus because their country is near this fort, and has gradually made himself a power with them. That's why he comes on his lonely visits—to see that Rabeh's hoard is safe. I don't suppose the Tubus know anything about it. It wouldn't suit his plans to inform them until he has made himself their absolute master."

Then his thoughts turned in another direction.

"How many villages were sacked, how many thousands of poor wretches were killed or enslaved in the gathering of this hoard? And Goruba is like his master in that, too—he is the same blood-thirsty tyrant and oppressor. But, please God, Tom will give him a shake.

"Ah! those skeletons—how did they come there?"

He pondered for a time without arriving at a conclusion.

"I see!" he said to himself at last. "They are the skeletons of the poor slaves who dug the passage Rabeh killed them to preserve his secret. Horrible! ... But I haven't discovered everything yet. Where is the entrance at the other end, by which Goruba reaches the cavern? I must go again—but not to-day. I can't face those skeletons again to-day; to-morrow, perhaps."

CHAPTER XXIII

GORUBA IS CAUGHT

On the morning after his discovery of Rabeh's hoard, Royce made a second visit to the cave to search for the exit which he felt sure must lead to the outer air.

Carrying a lighted candle, he walked slowly round the walls, examining them carefully. They appeared to be in their natural state—rough, irregular, knobby, but with no hole or gap large enough to admit a man.

Then he tried the floor. It consisted of slabs of stone. He tapped them here and there, but they gave no hollow ring; apparently they were solid. The ivory tusks were ranged in such orderly rows that it seemed hardly likely the entrance was beneath them.

Puzzling over what to do next, he suddenly thought of testing the place with the candle flame. If there were an opening, there must be a current of air. He returned to the slab in the wall of the well and closed it as tightly as was possible from the inside; then placed the candle at several spots on the floor of the cave, one after another, and, retiring to a distance, watched the flame for signs of flickering.

But he had no success; the flame only flickered in the current caused by his own movements.

"Where can the entrance be?" he said to himself. "The air is stuffy, but not foul. I'll try the passage."

He tapped the wall on each side; no sound rewarded him. Then he placed the candle on the floor near the threshold of the cave, and ejaculated "Got it!" when he saw the flame flicker gently. Hastening to the spot, he knelt down and passed his hand slowly over the slabs, and felt a distinct though slight draught at the seam between two of them.

He pushed at each of the slabs. They did not move. He got up, and jumped on them as forcibly as the low roof allowed, still without effect. Then, lifting the candle, he examined the walls.

At his left hand, near the roof, was a single staple, like those in the wall of the well. It could not be intended for climbing—what, then, was the use of it? Standing under it, he grasped it and pulled. It did not yield. Then he pushed, more and more forcibly. The staple did not move, but he fancied that the slab on which he was standing sank a little.

Looking down, he saw, just below the floor, a narrow jutting ledge of rock. With his left foot on this, he pushed at the slab with his right, still shoving at the staple with his hand. The stone began to revolve, slowly, with a slight grinding sound. Presently it stood upright in the middle of the passage, and moved no more.

Royce now saw beneath him half a dozen steep steps leading down into gloom. He descended carefully, lighting his way with the candle, and found himself in a passage, narrower than the upper one, but much cooler and less stuffy. From the direction of the cave there was a steady draught.

Moving against it, Royce, after about fifty paces, caught sight of a glint of light ahead. He pressed on eagerly, and discovered that the passage ended in an opening roughly circular in shape, about a yard in diameter. Passing on, he came out into a tangle of brushwood through which he saw trees. He forced his way forward, and stood in a clump of woodland. There was nobody to be seen, no sound. He stole cautiously among the trees until he came to the edge of the clump. It looked over open country. Glancing round, taking care to keep hidden from observation, he saw at last the fort, on the hill about two hundred yards away.

"This must be the clump we noticed," he thought. "Now I understand why Goruba has not used it for cover in attacking us. He doesn't want any of his men to discover the secret entrance to his hoard. Of course, with the slab down they couldn't find the hoard itself, but evidently he doesn't mean to be bothered with inconvenient questions. Well, Mr. Goruba, I have caught you out. I only wish I could catch you."

Royce made his way back quickly, feeling that he was perhaps risking a good deal in leaving the men so long. He carefully replaced the two slabs, ascended the wall of the well, much to Kulana's relief, and, having assured himself that the garrison were at their posts and that the enemy had made no move, he sat down to devise a trap for Goruba.

"I suppose the fellow will come again," he thought. "Why does he come at all? A visit to the cave and no farther would prove that his treasure is safe. I suppose his idea in penetrating right into the fort is to spy, perhaps to frighten the men into deserting me. I mean to stop your little game, my man."

His first notion was to place a couple of sentries in the cave, to catch Goruba on his next appearance. In the darkness the giant would not see them. But he soon gave that up. It would probably be better not to let the men know anything about the cave for the present. Besides, he could not tell when Goruba would pay his next visit, and the superstitious negroes would never endure a long wait in the dark.

After long puzzling, Royce hit on a plan that seemed likely to be successful. He attached a thin cord to the slab in the well, at a point where it would not be seen in the semi-darkness by any one entering from the passage.

Carrying the cord round the well, he passed it through hooks of his own devising—nails driven into the brickwork and bent almost double. At the top he fastened similar hooks to the wall of the well-yard, near the floor, drew the cord through them, and finally tied it to the topmost of a short column of empty meat tins in his own room.

When this was done, he went down to the well again, turned the slab gently on its axis, and in a moment or two heard a slight clatter as the tins were overturned.

"I call that a stroke of genius," he said to himself. "The question is, will the sound scare Goruba away? He is bound to hear it, though it is not so loud as I expected. But, after all, there is nothing to make him connect the sound with his own movements, so I fancy there will be a little surprise in store for him."

At dusk that evening he sat in his room, watching the pile of tins, and waiting eagerly for the alarm signal. But it did not come. All night he remained awake, unable to sleep from excitement. Not a sound broke the stillness.

Next evening he took up his post at the same time. Tired and sleepy, he was just falling into a doze when the tins fell with a crash that made him jump.

Pulling off his boots, he slipped very quietly into the well-yard and stooped below the top of the wall. He knew that he was in plenty of time, for the intruder was sure to move slowly and with caution.

With his electric torch in his left hand and his revolver in his right, he passed round to the side of the well opposite to where the staples were placed. In a few seconds he heard a slight rustle; the man was climbing over the coping of the well. He saw his form, a huge black shape against the dark blue sky.

The man stood listening for a moment, then crept towards the doorway leading to Royce's quarters. Royce stole on tiptoe after him, and just as he reached the opening pressed the button of the torch. The negro turned instantly, and the bright ray from the torch flashed upon the startled eyes of Goruba.

Royce had expected astonishment, even dismay. He was not prepared for the extraordinary readiness, decision, presence of mind with which the negro would act. Without an instant's hesitation, Goruba sprang at him with uplifted knife. Royce fired, but either he missed or there was no stopping power in the bullet, for in another fraction of a second he was hurled back towards the well, narrowly escaping toppling over the coping into its depths.

But if Royce missed, so did Goruba, dazzled, perhaps, by the light of his torch. His knife crashed on the coping, and was shivered to pieces. Next moment Royce found himself for the second time locked in the giant's embrace.

Exerting all his strength, he strove to prevent the negro from hurling him into the well. He shouted. Answering shouts came from the men. And then he discovered, to his surprise, that Goruba was not so formidable an antagonist as when they had first met. His grip was not so firm; all the pressure came from his left arm.

Encouraged by this, Royce grappled him closely, tried a back-throw he had learnt in jiu-jitsu, and had Goruba on his back as the Hausas, headed by Kulana, came shouting into the yard.

Royce was only just in time to prevent them from plunging their knives into the struggling negro. At his order, they tied him up with cords, so tightly that he howled with pain.

"Loosen them!" cried Royce. "Don't hurt him."

Kulana stared.

"Him hurt massa," he protested. "Him fit for kill all same."

"No; that's not our way," said Royce firmly. "We've got him, and we'll keep him safe. I hope this is the end of our troubles."

The Hausas, grumbling sullenly, carried Goruba into the passage next to Royce's room, and laid him against the wall. It was then found that his right wrist was sprained.

"He must have struck it against the wall when he missed me and smashed his knife," thought Royce. "That accounts for his feebler grip."

To the further disgust of his men, he bound a wet rag tightly round Goruba's wrist.

"Now for a good night's rest for once," he thought. "We shall not be attacked to-night, at any rate."

CHAPTER XXIV

A FIGHT WITH CROCODILES

In the afternoon after the fight with the Tubus, Challis was reclining on a moss-covered rock near the cave—he could not endure the atmosphere of that close-packed habitation.

He was thinking things over, wondering whether, after his first victory, he dared lead his men towards the fort to encounter the main body of the enemy under their redoubtable leader Goruba.

Suddenly he was aware of some excitement among the crowd of natives just beyond the mouth of the cave. Could the Tubus be returning to the attack?

He sprang up, intending to reassure himself on this point. But at this moment John came running towards him, his broad face contorted by a grin.

"What is it, John?" Challis asked.

To his surprise John burst into loud laughter, slapping his thighs, bending his body, now and then pointing towards the swamp and doubling with laughter again.

"Come, come, what is the joke?" asked Challis.

"Oh, my! Oh, dear! Oh my lawks!" spluttered the Hausa. "Ober dar, sah, ober dar."

"Well? Stop laughing, and tell me about it."

John controlled himself with difficulty.

"Ober dar, sah, two bad fellas!" A guffaw. "Tubus, sah. Up a tree, sah."

"There's nothing very funny about that."

"No funny? Oh my lawks! Up a tree, sah—no come down. Boys frow spears, sah. Berry funny, all same."

"This won't do," thought Challis. "I suppose the Tubus got away, and the men are trying to spear them instead of taking them prisoners. But it's strange. There was plenty of time for them to escape altogether when I called the men off. Why didn't they run away?" he asked.

"No can do, sah," replied John, laughing again. "Crocodiles wait for dinner."

"Goodness!" Challis ejaculated. "Are there crocodiles in the swamp?"

"Oh yes, sah! fousand hundred," answered John. "Sah come and see. Him laugh all same."

He preceded Challis towards the swamp, to which the whole population of the cave were now flocking like children running to see a Punch and Judy show.

Challis hurried on. Arriving at the edge of the swamp he saw, about two hundred yards away, two Tubus crouched in the branches of a low bushy tree, not five feet above the surface.

A number of the spearmen had gone forward as far as they dared on the spongy ground, and were gleefully hurling their spears at the negroes. The range was too long, however; the weapons fell short, and splashed into the water.

And then Challis saw that for some distance around the tree the swamp was almost like a lake. The water was evidently several feet deep. And the terrified Tubus, clinging to the branches of the tree, were gazing with horror at the snouts of half a dozen crocodiles which formed a half circle projecting a few inches above the surface.

Challis was almost as much horrified as the Tubus themselves. He knew the cunning and treacherous nature of the hideous beasts. He knew that usually they came upon their prey by stealth. It was a surprise to him to find that they were bold enough to attack men openly.

It was clear that the hapless negroes were hopelessly imprisoned. In the tree they were safe, but they could not descend and attempt to swim away without the certainty of falling victims. And the cave dwellers crowding at the edge of the swamp laughed with delight at their enemies' plight and, yelled with disappointment when the weapons of the spearmen fell short.

"Stop that!" cried Challis to John. "Tell them I am very angry with them for wasting their spears."

John shouted to the men, who shamefacedly drew back. They felt no shame at trying to kill a helpless enemy, but dreaded the wrath of the white medicine man.

"I must save the wretches," thought Challis. He meant to break the power of the Tubus if he could, for the sake of all the natives of the district; but he could not stand by and see two helpless men swallowed by these slimy monsters.

It was clear that they could not save themselves. The hungry crocodile is pertinacious; he will not leave his expected prey. Some time or other the men would fall off the tree from sheer terror or weakness into the very jaws of the reptiles.

Challis gazed across the swamp. The people, seeing that he did not share their merriment, fell silent, and watched him curiously.

The swamp was covered in patches with aquaceous plants; there was no other tree except that in which the negroes had taken refuge. It would be useless to fire at the reptiles. Only the tips of their snouts were visible; Challis could not be sure of hitting a vulnerable part. He tried a shot, but, as he expected, it had no other effect than to startle the crocodiles for a moment; the next, when the sound had died away, their snouts bobbed up again.

On the hillside behind the cave there grew a few small trees.

"John," said Challis suddenly, "take some men up the hill, cut down a dozen strong young trees, strip off the leaves, and bring the trunks here as quickly as you can, with plenty of creepers."

John started off with a band of men. The rest, excited at the prospect of seeing more big medicine, chattered noisily.

When the men returned, Challis set them to lash the saplings together with the creepers to form a raft. In half an hour it was completed. At his order they carried it to the verge of the yielding ground. The crowd, having an inkling of his purpose, shouted with delight. The white man, they thought, was going to bring back the Tubus to be slaughtered.

It was difficult to launch the raft from the soft boggy ground. The men shrank from entering the water. John explained that crocodiles had been known to snap up a man from the midst of a large party. To reassure them, Challis ordered some of the spearmen to stand by, and watch for the beasts while their comrades hauled the raft into the water.

When it was at last afloat, he wanted four men to paddle it. But when John selected four strong fellows and told them what they were to do, they yelled with fright, and fled back among the crowd.

"Well, we must do it ourselves," said Challis.

"All same, sah," said John.

But Challis noticed that he looked very uneasy. Only the desire to "show off" before the people prevailed over his fear.

The two got upon the raft, and standing well in the centre, poled out with saplings across the thick weedy water. Challis felt somewhat anxious himself when he realised how frail and crazy was this rapidly made raft. And they had only gone about fifty yards from the shore when he got some notion of the nature of the adventure on which he had embarked.

Almost without a ripple on the surface a snout emerged from the water a few yards ahead of them. In another moment a second and yet a third appeared. Then more came on each side and behind. The swamp seemed to be swarming with the reptiles.

Challis tried another shot. The snouts instantly disappeared, emerging again, however, after a few seconds, at a little greater distance. Whether Challis had killed one he did not know.

He was taking aim for a third shot when the raft, neglected by John, intent on watching his master, lurched against a half submerged bank of weed. Challis staggered, and in catching at John to steady himself, dropped his rifle, which struck the side of the raft and fell into the water with a big splash.

"Never mind," said Challis, trying cheerfully to hide his annoyance. "They can't get to us on the raft."

Coming into deeper water, they used the saplings as paddles. The crocodiles kept at a greater distance, but they followed the raft, swimming slowly and quite noiselessly after it as it crept towards the tree.

Challis felt the presence of this escort not a little disconcerting. He was not scared, but uncomfortable. He thought of driving off the reptiles by shouting; it was quite an effort to find his voice. When he shouted and splashed with his paddle there was a momentary scattering and disappearance of the snouts; but as soon as he left off, they came up behind and around the raft again.

He was heartily glad when at last they reached the tree.

"Tell the Tubus to come down," he said to John.

The Hausa jabbered to the men in the tree; they neither moved nor answered. He shouted to them again, still without effect.

"Plenty silly chaps," he said scornfully.

"Perhaps they think we shall kill them," said Challis. "Tell them we have come to save them."

It required a great deal of eloquence on John's part before the negroes were convinced that the white man wished to save, not to take their lives. Even then they hesitated from fear of the crocodiles. To encourage them John beat the water noisily with his paddle, all the time abusing them as "silly chaps."

At last they lowered themselves cautiously from the branches and stood clinging to each other in the centre of the raft. The crocodiles hovering round seemed to be conscious that their prey was escaping them, or, as Challis thought, felt that their dinner was assured, for they made a sudden dash at the raft. Some of them got their snouts over the edge, and while Challis and John belaboured them with their paddles, the Tubus fell on their knees and crouched howling.

The crocodiles sank into the water, and Challis and his man began to paddle shoreward with all their energy. But soon the reptiles, finding that they were none the worse for their battering, the blows of the paddles being but flicks on their tough hides, returned to the attack.

This time the danger was more serious. The slight raft rocked about and dipped at the rear as Challis and John smote desperately with their poles at the crocodiles, some of which had pushed their snouts and forelegs over the edge. The Tubus, who might have maintained the balance by going to the other end, cowered and howled in the middle.

Challis and his man had to withdraw from the edge in order to avoid being capsized, and the reptiles scrambled farther on. John's pole snapped on the back of the foremost, but he thrust the splintered end into the monster's eye. At the same moment Challis plunged his pole down the throat of another. The two strokes were almost too effective. The crocodiles slid back into the water, and Challis had only just time to spring forward and prevent the raft from overturning.

There was a brief breathing space. The monsters had disappeared. But the raft was stationary, and the poles were gone. It was impossible to propel it farther except by paddling with their hands. They were beginning to do this, Challis on one side, John on the other, when both started back simultaneously as the hideous snouts once more rose above the surface.

The scene had been watched with growing excitement by the crowd on shore. Realising the peril of the situation, some of the men began to hurl spears at the reptiles, which were again closing in behind the raft. This was more dangerous to the men than to the crocodiles. One of the spears fell on the raft. Challis snatched it up, telling John to order the men to cease throwing.

Three more of the monsters were now scrambling up, and under their pressure the raft moved towards the shore. Challis jabbed his spear at their eyes and gaping mouths. He disposed of them one after another. But his victory brought catastrophe. The third flopped off so suddenly that before Challis could step forward the raft tipped up, and all four men were thrown into the water.

The Tubus yelled, John shouted, the people on shore shrieked. Challis felt that all was over. Against these reptiles in their own element he could do nothing. He could only swim for it.

"Splash with your legs!" he cried to John, who, like the Tubus, was already striking out vigorously for land, now only fifty yards away.

The spearmen, aghast at the plight of their white chief, forgot their fears and dashed into the shallower water to save him, the crowd behind them yelling frantically. The tremendous splash, the din and clamour scared even the monsters. They sheered off and sank beneath the surface.

In a few moments Challis, slimy with weeds and green with ooze, was dragged up by his jubilant followers. John and the Tubus scrambled on shore unassisted. The crowd made a dash for the latter, but Challis sternly called them off, ordering John to look after them as prisoners of war. And then they all marched back to the cave, the people shouting and laughing with joy, though Challis felt by no means like a conqueror.

CHAPTER XXV

CHARGED BY RHINOCEROSES

On the day after the fight by the swamp, while Challis was exercising his men, some of the boys whom he had turned into scouts ran in with the news that a band of fifty or more armed negroes was approaching from the south-west.

Challis hoped that he would not have to engage a new enemy. Giving John orders to watch the newcomers, he went on with his work. By and by, out of the tail of his eye, he saw John talking to a group of strangers, who looked on at the drilling with the interest and curiosity of children.

It was plain that the newcomers were friends, and that John, with much self-importance, was eloquently expounding the virtues of white man's medicine.

When the drilling was over, John announced that the strangers had heard in their village, several miles away, of the defeat of the Tubus, and had come to see the white man who had punished them. He further explained that the negroes wished to join the forces, and learn how to march, advance, spin round, and use pikes like them.

While John was speaking, the scouts signalled the approach of a smaller band. Shortly afterwards, to Challis's amazement, a third party was announced.

It was a striking proof of the extraordinary rapidity with which news spreads in the wilds of Africa. Before the day closed, two or three hundred men had arrived from widely scattered villages, all eager to see the white man, and to learn something of his magic.

They were armed for the most part with spears. Challis saw in them the making of a very respectable army; but it was clear that, if Royce were to be relieved, there would not be time to give them even the very slight training of the earlier recruits. He did not, however, reject them. They would help to make a good show, and might come in useful, if not to achieve a victory, possibly to follow it up.

Before the night was over he had reason to doubt the wisdom of his decision. The new men belonged to different tribes, and were inclined to quarrel among themselves. Challis ordered John to quarter the various parties separately in the neighbourhood of the cave, hoping that by keeping them apart he would prevent disturbance.

But a new trouble arose. One of the bands got up a war dance around their camp fire, and worked themselves up to a fury of excitement. Then, having learnt the whereabouts of the Tubu prisoners, they made a rush towards them, and Challis was only just in time to prevent a wholesale massacre.

The ringleader, who had fairly lost his head, threw a spear at the Tubus in spite of Challis's stern command. It was clear that a lesson was needed. Challis doubled his fists, and with two well-planted blows, left and right, sent the man spinning.

"Tie him up," he said to John, "and keep a guard over him for the rest of the night. To-morrow I shall send him back to his village. These people must understand that they must do as they are told."

The fall of their leader sobered the rest of the band. They felt a great respect for the white man's fists, and remained peaceful until morning broke. Challis was sitting alone, waiting for John to bring his breakfast. When the Hausa came up, he was followed by a group of the negroes, looking anxious and sheepish.

"Silly fellas, sah," said John with a grin. "Dey say Umgabaloo berry fine fella, sah. No want him to go back."

"Oh! He's sorry for himself, perhaps; wants me to forgive him."

"Dat's him, sah. Just a silly chap. No savvy good things like me; no savvy sah knock him down."

Challis could not help smiling at John's notion of "good things." He reflected. It was said that negroes respected nothing but force; that they took forgiveness as a sign of weakness. Would it be wise to pardon this Umgabaloo, who seemed popular with his friends?

"I'll risk it," he thought. "Bring Umgabaloo to me," he said.

John fetched the negro, marched him up, and stood him before Challis, keeping his hand on the man's neck. Umgabaloo looked very crestfallen.

"Tell him that he's no good to me unless he can do what he is told," said Challis.

John translated this with forcible additions.

"Tell him I'll let him off this time if he'll promise to obey," Challis went on.

When John made this announcement, Umgabaloo's friends shouted, and the man himself tried to move forward, but was brought up by John's determined grip.

"Does he promise?" asked Challis.

"Him say, Sah him father and mother," said John, "do eberyfing what Sah say."

"Very well; let him go."

Umgabaloo, released, threw himself at Challis's feet and poured out a torrent of thanks and protestations.

"I wonder if I've done right," thought Challis, as he dismissed the man.

He had decided to make a start for the fort that day, while the impression made on the enemy was fresh. At his orders, every man loaded himself with four days' provisions from the ample stores in the cave. Then he drew up in column the men whom he had already led to victory, and the newcomers tried to arrange themselves in similar formation behind, but were too much excited to be very successful.

Challis had now between three and four hundred men at his command. They were still largely outnumbered by the Tubus; and what was of still more consequence, they were not so well armed. In the recent encounter he had been able to choose a good tactical position; such a chance was not likely to occur again. No doubt, moreover, the Tubus, warned by their defeat, would move more cautiously, and, being mounted, they would take advantage of their mobility to fight on ground of their own choice.

These considerations, and the desire to avoid bloodshed, influenced Challis's plan. His object was to reach the neighbourhood of the fort unobserved, to communicate with Royce, and if possible to secure a peaceful withdrawal. He therefore decided not to follow either the route by which he had come, or that taken by the Tubus when they made their ill-fated attack.

As his orderly, John had distributed among the best of the men the rifles and ammunition captured from the Tubus. But Challis commanded them on no account to use these weapons without orders. No warning must be given to any Tubus who might be scouting along the route.

All being ready, he went to the head of the column with a man who knew the country well and would act as guide. Then the whole party set off in a north-westerly direction, to skirt the swamp and cross the river some distance to the west.

The first stage of the march was very difficult. The negro knew paths across the swamp which a stranger could hardly have discovered, but even so progress was slow and laborious. The men had to go in single file, sometimes over boggy land close to the water's edge, keeping a wary eye for crocodiles; sometimes through rushes as tall as their heads, from the midst of which they disturbed game of all kinds, birds and beasts.

They had been some two or three hours on the march, and had got round to the far side of the swamp, where the ground was drier and firmer, when Challis saw the guide, some few yards ahead, suddenly halt and make signs to him to be cautious.

Wondering if the Tubus were in sight, Challis halted the column, ordering the men to be silent, and walked warily forward. When he came up with the guide, the latter pointed to the path about a hundred yards in front. And there Challis saw, not Tubus, but two enormous square-mouthed rhinoceroses, lying in the mud right across the path.

At the moment he caught sight of them the great beasts scrambled to their feet, turned their heads in his direction, and snorted. They had evidently scented him.

Knowing that the rhinoceros is usually a timid and inoffensive creature, living on herbs, and not a flesh-eater like the lion, Challis expected the beasts to sheer off. But these animals, like other denizens of the wilds, are sometimes driven into hostility and aggression by alarm.

There was a moment of suspense. Then the rhinoceroses raised their blunt-horned heads, snorted again, and came at a lumbering charge straight for the head of the column. The guide shouted and threw his spear, which glanced off the tough hide of the first, then he uttered a yell and bolted.

Challis had only an instant for making up his mind what to do. On one side of the path was yielding bog, on the other was drier ground, dotted with bushes. The path itself was blocked by the halted column. He dared not use his rifle, for fear of giving warning to the enemy. The leading rhinoceros was charging straight towards him. The only chance of safety was to run.

He turned and sprinted across the open ground. The rhinoceros, infuriated by the guide's spear, swerved off the path and followed him. Its companion headed straight along the path.

In a few seconds Challis found that the beast, in spite of its size and unwieldiness, was gaining upon him. He darted aside when it was close behind him, expecting that it would continue in its half-blind charge. To his alarm it struck off almost immediately in his direction.

There was no friendly tree in sight. The rhinoceros broke through the bushes as if they were cobwebs. Challis dodged, first on one side, then on the other, but the beast showed an alarming nimbleness. More than once Challis escaped its formidable horn only by inches.

Running on in desperation he stumbled, and had given himself up for lost when he was conscious of a diversion. A dark form, running with extraordinary speed, dashed obliquely towards him, and buried a spear deep in the animals' side. It turned savagely to deal with this new assailant, who had darted off at an angle. For a few yards the rhinoceros followed him, then it staggered, made a vain effort to recover itself, and fell a huge heap upon the ground.

The negro rushed back, plucked out his spear, and driving it again into the quivering beast dealt it a death-blow. Challis went up to him. Umgabaloo fell on his knees.

"I was right," thought Challis, glowing with pleasure. "Any one who says that the negro knows no gratitude lies."

Meanwhile the column had scattered far and wide to escape the second rhinoceros, which had apparently taken fright at the number of men, and had now disappeared. It was an hour before the negroes were collected and the march resumed.