"You're not going to blow down the hill?" "Hope not, I've taken a baby bomb, but I didn't wish to let it off till I'd told you what to expect. I'd keep away, in case of flying pieces." "I will," said Elaine. "But I'll go up now, and perhaps you can call to let me know how well you have succeeded." "I'll send you a wireless." Grenville hastened to his raft. "Please God she may never have to hear me fire another!" he thought, as he went, reflecting on things that might happen. He could not have known that only a mild beginning had been made on their programme as scheduled by the Fates. He was soon rowing eagerly and vigorously against the current of the tide, which would run with lessening velocity for perhaps another hour. When he came to the cave, he promptly discovered why the injunction to enter its mouth at high water only had been made a point in the mystic directions found with the map in the tube. The ledge whereon he had landed before was deeply undercut. During a tide no more than two or three feet lower than this that would serve him to-day, the place could scarcely be approached, and could never be entered at all. The swirl, which was rarely ever absent from the place, increased in violence steadily with the lowering levels of the water. It was not without some chance of catastrophe that he presently landed on the shelf. He lost little time in securing his painter to the rocks, the line so adjusted he could readily slip it from the crevice should a hasty retreat seem wise. The task of blasting out the ledge was not a simple matter. To lodge the bomb where its energy would be directed almost wholly against the dam, or rock, and yet protect it from the trickling stream that could readily render it useless, involved an extra toil of piling rocks, on which he had not reckoned. Fortunately, much of the thickest wall was opposed to the pot-hole in the dam, while one or two extra-heavy fragments from the cliff were so lightly poised he could drop them in the breach. Despite these natural advantages, however, he labored hotly for fully half an hour before he could even lay his fuse. Meantime, his torch was blazing smokily, against his final need of igniting the match and later exploring for results. At length he looped the fuse along a ragged line of broken honeycomb, where pits had been eaten in the tufa, and trailed it well down to the brink of the ledge, with its end propped high between two bowlders. With one last look at all his careful arrangements, he slipped off his raft-line, caught up his torch, and was stepping down to board his float when a sharp piece of rock broke away beneath his foot and dropped him forward on his hand. The torch was flung against the fuse, where it lay along the slope. He heard it hiss, where the powder had caught, and aware that, by three or four feet, it was shorter now than he had ever intended to light it, he lurched full-length upon his raft and fumbled to clutch up the oars.