“‘Quitting air, must pass through water.’ The meaning of those words became apparent enough. I stood at the foot of the waterfall, looking up at the fissure from which it issued.  
“Although the fact had been most artistically disguised, I could not doubt that this fissure was artificial. A tunnel had been hewn through the rock, and a mountain stream diverted into it. Indeed, on close inspection, I saw that it was little more than a thin curtain of water, partly concealing what looked like the entrance of a cave.
 
“A great deal of mist arose from it. But I could see that, beyond a ducking, I had little to fear; and, stepping down into the bed of the little stream which frothed and bubbled pleasantly about my bare legs, I set my bundle on my head as the mendicant had done, and plunged through the waterfall, into a place of delicious coolness.
 
“A strange greenish light prevailed here and directly before me I saw a flight of stone steps leading upward through a tunnel in the rock. By the light of a pocket torch with which I had provided myself, I began to ascend the steps. These, as I have said, were hewn out of the solid rock, and as they numbered something like seven hundred, the labour expended upon the making of this extraordinary staircase must have been stupendous.
 
“At first the character of the surrounding tunnel suggested that it was, in part at least, a natural cavern. But as I mounted higher and higher, solid masonry appeared in places, some of it displaying unusual carvings, of a character with which I was quite unfamiliar. I concluded that it was very ancient.
 
“I should explain, gentlemen, that this ascending tunnel zigzagged in a peculiar fashion, which may have been due to the natural formation of the volcanic rock, or may have been part of the design of the original builder. I had ascended more than five hundred steps, and felt that a rest would shortly be necessary, when I reached a sort of cavern, or interior platform, from which seven corridors branched out like the spokes of a wheel. The top of this place was lost in shadows, which the ray of my torch failed to penetrate; and here I paused, setting down my bundle and wondering what my next move should be.
 
“To the damp coolness of the lower stairs an oppressive heat had now succeeded, and I became aware of a continuous roaring sound, which I found myself unable to explain.
 
“Attached to a belt beneath my native dress I carried a Colt revolver; and therefore, leaving my rifle and bundle in a corner of the cavern, I selected one of these corridors more or less at random, and set out to explore. This corridor proved to slope very gently upward from the platform, and I could not fail to notice that at every step the heat grew greater and greater. A suffocating, sulphurous smell became perceptible also, and the roaring sound grew almost deafening. It became possible to discern the walls of the corridor ahead because of a sort of eerie bluish light which had now become visible.
 
“Gentlemen, I don’t say that I hesitated in a physical sense: I went right on walking ahead. But a voice somewhere deep down inside me was whispering that this was the road to hell.
 
“At a point where the heat and the smell were almost unendurable the corridor was blocked by massive iron bars beyond which the reflection of some gigantic fire danced upon the walls of a vast cavern.
 
“The heat was so great that my garments, saturated by the curtain of water through which I had passed, were now bone dry, and I stood peering through those bars at a spectacle which will remain with me to the merciful day of my death.
 
“A hundred feet beneath me was a lake of fire! That is the only way I can describe it: a seething, bubbling lake of fire. And above, where the roof of the cavern formed a natural cone, was a square section formed of massive stone blocks, and quite obviously the handiwork of man. The bars were too hot to touch, and the heat was like that of a furnace, but while I stood, peering first upward and then downward, a thing happened which I almost hesitate to describe, for it sounds like an incident from a nightmare.
 
“Heralded by a............