A little later, becoming dissatisfied with his position, Grenville drew his party back some fifty yards under the cover of a rock, and then proceeded to act in a most singular manner. Divesting himself of his hat, jacket, and hunting-shirt, he slipped a brace of six-shooters into his hip-pockets, and, directing Leigh and the Zulu to stay where they where—unless they heard him blow a small whistle, which he always carried—he left the pair wondering at his extraordinary movements, and gradually and cautiously approached the Fall. Arrived there, his conduct became curious to a degree, for, lying flat on the rock, on the very edge of the basin indeed, where the spray from the cataract fell in a continuous and blinding shower, Grenville first commenced feeling about inside the rush of the water at the very back of the Fall, and finally buried himself, head and shoulders, in the water of the basin, frequently raising his head to take breath. After he had expended quite ten minutes in this edifying manner, he gave a grunt indicative of satisfaction, rose dripping wet, and retired into concealment behind the nearest rock, watching the Fall like a lynx.

Soon his patience was well rewarded, for a wonderful and beautiful thing happened. In a single instant the Fall grew gloriously light and beautiful, and the foaming, flashing surface of the water seemed by the touch of some fairy wand transformed into a stupendous rainbow of indescribable loveliness, as the changing lights appeared to come and go through the driving rifts of steaming, gauze-like vapour.

Grenville smiled, and made himself, if possible, still smaller amongst the stones; a slight splashing was heard, and in another moment the light went out suddenly and the Fall resumed its normal appearance—a white, angry-looking streak of sliding foam, clearly outlined against the dark background of rock. And now Grenville could see by the starlight the forms of fully a dozen men who appeared to have sprung from the earth; crouching down, he lay for some moments breathless and motionless as the rocks beneath him, but, hearing no footsteps, and cautiously raising his head, he found no one within his limited range of vision. Hazardous though the act was, Grenville crawled out, snake-like, to the spot where he had seen the strange party take its stand, and, by following the damp feel of the rock where wet footsteps had passed, quickly satisfied himself that the enemy had proceeded down the Pass. Quietly rejoining his anxious friends, he led them back, after a brief consultation, to the basin at the foot of the Fall, into which each silently dropped in turn, and instantly vanished from sight.

A few moments later three dripping, panting forms stood whispering together upon a rocky ledge, which was in fact the entrance to a vast cave, by which, as Grenville had cleverly surmised, their assailants passed through the base of the mountain-range and obtained access to their mysterious country beyond.

The air, though dense with a heavy, noxious odour, was still very refreshing to the party after their dive; but Grenville soon reminded the others that they had no time to lose, and, warning them to look to their arms, ammunition and matches, all of which had been most carefully enveloped in mackintosh ground-sheets, himself proceeded to strike a light. Now the striking of a match is a very trifling affair at ordinary times, but, with a dark and doubtless vast unknown before them, each waited anxiously to see what the tiny flame would reveal. One brief instant it shed its feeble light upon their pallid faces, then, in an endeavour to pierce the apparently limitless gloom, Grenville raised the match above his head, and at that very moment there was a wild, hissing rush, and the cavern stood revealed in a blinding glare of light. The match had evidently ignited by accident a reservoir of natural gas, and this, in the shape of an enormous stream of fire, now hung globe-like from a rift in the roof of rock, where it arched a score of feet above their heads.

One glance was sufficient to tell the merest novice in such matters that this cavern had at some distant date formed the channel of one of those underground rivers by no means uncommon in Africa. What had been the bed of the stream was, however, filled in with earth, and was now to all intents and purposes a very passable road, which, after mounting a short hill that served in fact to keep back the water from the basin, ran straight before them as far as the light could penetrate.

The first act of the whole party was to remove themselves from the intense heat thrown out by the gas; their next, to draw their pistol-cartridges and slip fresh ones into the chambers; and hardly was this done when a startled exclamation, uttered just behind them, caused all to turn hurriedly, only to find themselves confronted by a most repulsive-looking white man, who stood dripping unpleasantly upon the rocky ledge and regarding them with a scowling face.

The newcomer appeared altogether unarmed, and our friends promptly rushed at him; but he incontinently turned tail, and dived out through the entrance, followed like a flash of light by Myzukulwa.

The cousins waited in anxious suspense for close upon a minute, and then the great Zulu silently appeared upon the rock and lay gasping for breath. Soon, however, regaining his wind—

“Inkoos,” he said, “he was too quick for me; the coward ran away down the pass; but first he fired his gun, and it was answered by another gun a mile away.”

It was quite clear that the man had been a sentinel near to their old sleeping-place, and, seeing the Fall suddenly light up of its own accord, had come down to examine the unusual phenomenon.

The three now fell to eagerly discussing their position. If they were holding the only entrance to the passage, they could with their revolvers defy almost any number of men attacking through the water; but if, on the other hand, there was more than one way of access to the cave, or if another hostile body, attracted by the firing, should come up the river Pass, our friends would be placed between the devil and the deep sea with a vengeance.

Then, again, if the foe had any means of extinguishing the light from outside, the trio would be entirely at their mercy.

This light was evidently a pure gas generated in the mountain, and used by these strange people to light them to the entrance of the cave; but how they extinguished it, and how without its help they followed their subterranean road through the absolutely inky gloom, was a mystery to the adventurers.

On looking about, however, they discovered a bundle of torches made of a resinous woody fibre, and lighting one of these in the gas-flame, Grenville proceeded to examine the road and see what cover, if any, it might offer. Hardly had he taken a dozen steps when a stream of water poured through the fissure in the roof of rock, extinguishing the gas in an instant. Grenville quickly whispered to his friends to bring the torches and follow him, as without proper light to shoot by it was impossible for them to hold the entrance to the passage. “Bring every single torch you can find,” he said, “and keep your eyes skinned for any more lying about the road. We’ll keep these beggars in darkness if possible; and once let us get to daylight, and we’ll fight them if need be.”

And now by the light of one torch the party proceeded in single file at a good speed, for the roadway was fair, and, when the first hill had been climbed, proved decidedly on the down grade. This surprised Grenville, as he had been of opinion that the water had formerly come from the inside of the cavern and emptied itself into the basin; the reverse, however, had evidently been the case.

After they had travelled about half a mile, the road, to Grenville’s delight, twisted almost at a right angle—this would, of course, hide the light from their pursuers—and directly after the turn had been negotiated, Leigh called attention to a niche in the rock where