I don’t think many could have stood peering into that gloomy tunnel without feeling something like a tremor of dread.  However, I mastered it at last, after asking myself the question, Was it wise to run such a risk?  The answer came in the shape of gold ­it might be the passage to traverse to arrive at inexhaustible treasure, and I turned to Tom.

“Are you ready?” I said.

“Yes, Mas’r Harry, I’m ready when I’ve lit my pipe,” he said.

And coolly filling it and igniting it from the torch, he crept boldly on to the little raft and took a bamboo, one of two cut on our way here, to pole us along.

After placing our guns in safety upon a ledge of rock, I crept on too, and the little raft swayed down heavily; but it was wonderfully buoyant, and with our lights in front we prepared for our subterranean passage.

“All right, Mas’r Harry?”

“Yes,” I replied.

And then we pushed off, poling ourselves along under the arch, the rugged wall being easily reached on either side, the stream widening and not being very rapid after we had passed the first dozen yards.

The navigation proved so easy that we were able to glance about at the sides and roof, which often nearly touched us, compelling us to stoop, while at other times the tunnel opened out and we seemed to be making our way through a narrow lake.  But it soon contracted again, and I should think our onward progress must have been through the damp, dark, winding way for quite a couple of miles; when, after seeing nothing but shining, glistening rock above us for hours, we seemed to have come to the end of our uneventful journey in a large irregularly shaped chamber whose roof of veined rock was about forty feet above us, its length being about two hundred feet, and its greatest breadth about sixty.

The stream had widened out into a little lake again, leaving, however, on one side a sandy shore some six or eight feet wide.  The waters were troubled, as if in a state of ebullition, and for a while we sat wondering and listening to a loud moaning roar coming apparently from a distance.  Then pushing on by the side, in a manner of speaking we coasted round the place till we reached the sandy shore and rested; for though the water flowed out through the arch by which we had entered there was no way of further exit from the great vault.

This, then, was the extent of the cavern river, and it was with disappointment that I went slowly round once more, poling the raft over the troubled waters, to find that there was no likelihood of a discovery here.  The sandy shore was the only landing-place, and unless the treasure was buried there I could see no other spot where a search could be made.  As to the lake’s profundity, of that we could tell nothing, only that at every attempt to touch bottom we withdrew our poles with a shiver.

Here, then, was the source of the river, which rose from springs somewhere far below ­springs which caused the bubbling we saw, making our little raft to rock terribly in one part we passed over, so that we gladly sought the sandy shore and there remained listening to the lapping of the water and the faint distant roar.

“There must be another cavern beyond this, Tom,” I said after a thoughtful pause.

“Ain’t a doubt about it, Mas’r Harry,” he replied.  “It’s my belief that if any one would do it he might go on for ever and ever, right through the inside of the earth to find it all full of places like this.”

“Look!” I said eagerly, as I stood on the sandy slip of land and held up the light above my head, pointing the while to the end of the vault; “there’s a rift up there, Tom, if we could climb to it, and that’s where that roaring noise comes through.”

“Mean to try it, Mas’r Harry?”

“Yes,” I said, “if we can climb to it; otherwise we must come again with something we can fit together like a ladder.”

“Oh!  I can get up there, Mas’r Harry, I know,” said Tom.  “I’ve been up worse places than that in Cornwall after gulls’ eggs.”

Tom sprang ashore, and I gave a cry of horror, for the little raft was moving off; but with a leap Tom was back upon it and drew it ashore by a piece of line, which he tied to one of the poles after forcing it well down into the sand.

“That won’t get away now, Mas’r Harry,” he said.

And then stepping cautiously along over the sand, which gave way and seemed to shiver beneath our feet, we reached the end of the vault, and with very little difficulty climbed from cranny to cranny till we gained the opening ­a mere slit between two masses of rock ­through which we had to squeeze ourselves, and then wind up and up between block after block, that looked as though they had been riven asunder in some convulsion of nature.

Two or three times we were for going back, so arduous was the ascent; but determined to see our adventure to the end we pressed on and on, ever higher, till the noise became almost deafening, a cold dank wind too made our lights to flutter, and once they threatened to become extinct.  But five minutes after the passage widened and the draught was not so fierce, while bright veins running through the rock at my side whispered of some rich metal or other for him who would venture thus far in its search.

“We’re a-coming to it now, Mas’r Harry,” said Tom shouting, for the noise was deafening.

The very next moment we were standing in a vast vault stretching out as far as our feeble light would show us, while about fifty feet to our left, in one black, gloomy, unbroken torrent, fell from some great height above, a cascade of water, black as night, till it reached the basin below us, which, even with our trembling lights, shone forth in a silvery, iridescent foam.

We could hardly hear the words we uttered from time to time, but we felt but little inclination to speak, so awe-inspiring was the scene before us; and it was not until we had been gazing for some time that we ventured to climb down lower and lower, to find that the bottom of the cavern was a basin of restless water, from which it was evident some portion escaped through a natural conduit to the vault below, while probably the rest made its way to the vast gulf we had before seen.

Then up and down ­now near the great foaming basin, then with arduous climbing close to the dome that formed the roof ­I searched about, well aided by Tom, who seemed to think that I was looking for something precious, though he said nothing.  At one time we approached so near the waterfall that we could distinguish, high up, the narrow archway through which it gushed.  It seemed, too, that by a little management any one daring enough might have passed round the rocky amphitheatre in which we were, right beneath the waterfall to the other side, where rifts and faintly-discerned chasms whispered of further wondrous passages unexplored, and I felt sure ­for the more I searched the more the feeling came home to me ­that we were the first human beings who had ever entered this stronghold of nature.

With the exception of the bright veins I have mentioned there was no trace of gem or precious metal.  The sides and roof sparkled and glistened again and again, but it was only with some stalactitic formation ­beautiful to the eye, but worthless; and at last I felt that this was labour in vain ­the treasure was no more here than in the vast chasm where we had hurled the stone; and, shouting to Tom my intentions, we stood and had another look, and then lit upon a mass of rock a large piece of oily oakum which we had brought for the purpose.

Our oakum burned brightly, but it was of little avail, giving us not much more than a glimpse of the wonders of the grand chamber in which we stood; and then we turned to go, but only to encounter an unexpected difficulty.  The chamber was so vast and the rift by which we had entered the sloping side so high up amidst crags resembling one another that we had great difficulty in finding it, and I remember shuddering as I thought of the consequences of being lost there in the dark.