"Echo," said Brown.
Morton tried again with the same result.
Brown fired his pistol, but the thunder of the echoes was the only answer.
"They must be poisoned with foul air," said Morton, in tones of the deepest sorrow.
"Must we wait until daylight?" asked Brown.
"I am afraid so. We might come to grief ourselves, and then it would be all up indeed. However, I think I can get down to the edge of the fissure without much danger, if you and the two blacks can hang on to the surcingles."
The preparations were soon completed, and Morton carefully made his way down the sloping sides of the hole and amongst the mud-encrusted boulders, by the help of the surcingles, which Brown and the two natives held above. It was slow work, for the candle he had gave out only a feeble light, but at last he found himself at the edge of the rift at the bottom. He stood there listening for some time; presently, with an up-blast of cold air that nearly extinguished his candle, came a strange wail as though some giant was sighing, far underground.
"Hear anything up there, Brown?" he shouted.
"Not a sound. Are you on level ground, can we slack off?"
"Yes, slack off. But do you think you could trust the two blacks to hold it while you come down? I will come back and show you a light."