"It comes to the same thing," Beresford went on imperturbably; and Forrester felt a little sorry that the man of cheery good fellowship was for the time sunk in the man of science. "Here there is none of the elaborate apparatus of the experimenter; but Nature has been experimenting through ages beyond count. What do our men of science know of the real nature of the X-rays? Next to nothing. They can produce them, that is all. And here, before our eyes, we have phenomena produced, not by man, but by the Great Artificer of the universe. Those creatures are swimming in the lake which you skirted just now. Their images are cast in some marvellous way upon this particular portion of the wall. I know no more than you the explanation, but.... My dear fellow, pardon me: this is not a lecture room. Come, I have something more to show you."
They recrossed the cavern, which was as broad as it was high, and turning a corner, were confronted by the arch-like opening of a passage. It was much more brightly illuminated by green light than the cavern out of which it led. Passing under the arch, the two men walked quickly up the passage, which twisted to right and left at every few yards, and inclined gradually upward.
"I feel very rummy," said Forrester after a while: "the sort of tingling you have before a severe thunderstorm."
"I feel it too," his companion responded: "not so intensely as you, perhaps. The thing is to keep as tight a hold on yourself as you can--as you ought to have done when that old sinner above hypnotised you."
"But----"
"Now don't talk. We shall have plenty of opportunities of discussing him, and hypnotism, and a thousand and one things. Take a grip of yourself, and will that the mephitic influence shall not affect you. You won't thoroughly succeed, but the effort will be good."
The feeling of tenseness increased as they advanced. To Forrester it seemed as though a hot band were tightening round his temples; but he kept silence. Glancing at Beresford, he perceived on his face an expression of grim, almost savage, determination. They went on, the passage becoming lighter moment by moment, until, after they had walked a few hundred yards, it widened out into a cavern, much less spacious than that which they had left, but almost as light as open ground at noonday. At the edge of it Beresford halted.
"Stand here, and watch," he said.
In the centre of the floor there was a large square slab of some greyish substance--the only spot in the cavern through which the green rays did not, as it were, percolate. It was about three feet each way, and stood a few inches above the floor. Upon it lay a coil of thin yellow-green chain, like an immense brass watch-guard tinged with verdigris, and an oblong lump about a foot in length, and of the same colour. A few feet above, a stout bar of yellow metal projected from the wall of the cavern, having at its free end, exactly over the centre of the slab, a wheel over which another chain hung.
These objects first caught Forrester's attention, no doubt because they formed a group in the centre of an otherwise bare floor; but they held it only for a moment or two. His eyes were diverted to a living figure. From a hitherto unnoticed recess on his left hand came a bent, decrepit, cadaverous Chinaman, to all appearance very old, carrying a thin square plate, in colour a dirty greenish-grey. He toddled slowly towards the slab, looking neither to right nor left, laid the plate upon it, and passed through a hole in the centre of the plate what seemed to be a small catch in the aforesaid lump of metal. This latter he attached to the chain hanging over the wheel.