For a little over a mile he strode on between the cliffs, then a bright light ahead warned him that he was approaching the end of the defile. Redoubling his caution as he advanced, he soon emerged from the gorge into another valley, much smaller than the one he had left, but lit by the same weird growths. At first he hesitated to advance into the light, the memory of his recent fright being still very vivid; but, putting a bold face on the matter, he moved forward at length from the shadow of the cliffs. As he stepped into the light of the luminous growths, clear and distinct to his ears came the clang of a bell. He pulled up short in sheer astonishment, and stood listening for a repetition of the sound. Clang! Once more it rang across the valley. Drawing his sheath-knife, Wilson moved forward, determined to investigate the mystery. What could be the meaning of the sound, he pondered? Had he reached the haunts of the wolf-men, and was the ringing of the bell some signal? Whatever it was he was resolved to get to the bottom of it. Clang! For the third time the musical note echoed amid the cliffs. The sound seemed to rise from a dense thicket of fungi, which covered the further end of the valley, and towards this the engineer hurried. Amid the towering growths he threaded his way, moving cautiously, having no wish to fall foul of any savages; then, with a low exclamation, he checked himself upon the edge of a clearing. Before him, tottering in the last stage of decay, rose a ruined building. Gaunt and ghostly, its roofless walls stood, the relics of some past civilisation. Fascinated, Wilson moved nearer. What was the history of this crumbling pile, the one sign of civilised life that he had seen in this underworld? For what purpose had it been erected, and by whom? The pillars, which once had graced its front, lay half buried in the spongy ground. Climbing fungi ran riot in the gaping cracks in its walls, and its stone pavement was covered with a carpet of moss. Its air of desolate grandeur strongly impressed Wilson, and for a while he forgot what had brought him thither. His engineer’s eye took in the monstrous size of the blocks which had formed the walls, and he marvelled how they could have been raised to their places. Surely they who erected such a building must have been men of gigantic stature and strength, unless indeed they were equipped with the appliances of modern engineering? Dare he enter? The place seemed as deserted as the grave. If there were savages about, they would, without a doubt, have shown themselves ere now. He longed to examine the ruins more closely. There appeared to be no danger, and, if it came to that, he was not safe where he stood. Thus reasoning, curiosity got the better of his prudence, and he strode across the clearing.