Hopeful of some enlightening sign as to who or what they might have been, he searched the earth about and between the shrubs and grasses with considerable care. Not so much as a bone, however, rewarded his scrutinizing gaze. He came to the tree trunk left hollow by the flames, and paused to marvel at its size. Above his head it was four feet through, while the base was certainly eight. An arch had been formed in its substance, near the ground, and into this he curiously peered. Kneeling thus on the earth, he was readily enabled to look straight up through and out at the top. The hollow in the stout old jungle champion was fully two feet in diameter, and almost perfectly round. There was nothing else of interest to be found about the place, save a huge, smooth log, lying with one end resting on a rock, and long enough to make a splendid boat. Attempting the passage of the jungle from this point across to the midway wall of tufa, Grenville expended fully fifteen minutes of the toughest sort of effort, and was then obliged to retreat once more to the trail. He encountered here the first wild animal discovered since his meeting with the tiger. It was a porcupine, bristling with trouble for any attacking beast. Grenville could have slain it with his club. He was fairly on the point of providing this much meat for the sadly empty larder, when the fact that he could ignite no fire deterred his ready weapon. He thought, in that extremity, of his watch, the crystal of which might serve to give him a white-hot spark from the sun. Trusting the porcupine might await the result of his quick experiment, he lost no time in submitting the glass to a trial. It formed a ring of brilliant light on the back of his hand, but the rays would not come to a focus. "Go thy ways," he said to the porcupine, and he continued at once on his own. Observing the trail more closely than he had on his earlier excursion, he presently discovered a divergence to the left that led towards the central wall of stone. Here he frightened a considerable troop of monkeys that swung in a panic of activity through the avenues of foliage overhead. There were likewise sounds of heavier beasts that escaped observation on the moist and thickly cumbered earth. The trail under foot was rather well worn, and not, the man was certain, by the hoofs or feet of brutes. The explanation was presently forthcoming, at least in part, for the path emerged at a clay pit that lay against the frowning tower of stone. Grenville could have shouted for joy as he took a bit of the smooth, sticky substance in his hand, and began thus promptly, in his fancy, making pots and jugs innumerable to meet their every need. The deposit had been previously worked. The evidence of this was unmistakable. But none of the tools employed by former craftsmen had been left for Grenville to discover.