"I think we have come upon the explanation of the island's uninhabited condition," he informed the girl, as he came once more to her side. "Those noises are made by the sea, forcing air to some cavern in the cliffs. It is doubtless repeated twice a day at a certain stage of the tide." "It's horrible!" Elaine replied in dread, as a feebler rehearsal of the chorus filled all that tropic breeze, "simply horrible!" "It may be our greatest bit of good fortune," Grenville informed her, sagely. "I much prefer those sirens to a colony of Dyaks who might otherwise live on the place." "We shall have to endure it twice a day?" "Possibly not. I may be entirely mistaken, concerning that. I can only be certain it is caused by the tide, and is, therefore, not to be dreaded." For fully ten minutes, however, the tidal conditions were favorable to the sound's continuance. It subsided by degrees, the last moaning notes possibly more suggestive than the first of beings perishing miserably. Meantime Grenville had gone indifferently about the business of cutting huge armfuls of the tall grass and ferns abundantly supplied in the clearing. This moist and not unfragrant material Elaine in silent helpfulness carried to the top of the terrace, where she spread it about on the rocks. She was certain Grenville was providing far more than they could use in reason, yet although his stubby knife-blade was a poor tool, indeed, for the business, he toiled away unsparingly, blithesomely whistling at his task. "You may be glad by nightfall to burrow into a stack of this hay," he told Elaine as he brought the last load up the trail. "If you wouldn't mind turning it over from time to time I think I'll look about again to get an idea of the island." Elaine had as little inclination to remain on the terrace alone, with all manner of worries respecting Grenville's safety, as she had to follow where he would lead through the shades and thickets of the jungle. She was aware, however, her presence at his side would be more of a care than assistance; while the necessity for his explorations addressed itself clearly to her mind. She made no confession of her natural wish to see him returning promptly. He departed, with his club in hand, quite certain he should not be gone above an hour. He had not, however, reckoned with the jungle. Despite the fact he had set his mind on the region about and beyond the spring, the flow of which formed the estuary, some wonder respecting the area once blackened and cleared by fire attracted his attention immediately upon his descent from the hill. Through a fringe of scrub he forced his way to this region close under the walls, discovering old, charred stumps, many dead saplings, and quantities of half-consumed branches, affording a large supply of fuel. There could be no doubt the fire had raged within the previous year. Human visitors of some complexion had come, left this scar, and departed.