"Listen hard, Filippo!" he exhorted. They strained their ears. No sound. The swell was so gentle that it did not break on the ledges of the island loudly enough to be heard a mile and a quarter off. The heaving circle of which they were the center was contracting fast. Its misty walls were now less than five hundred feet away. "Guess we'd better take a buoy aboard, and hang to it till Jim comes out to hunt us up. It'd make me feel cheap to do it, but it's the only safe way. But wait! What's that?" Both listened again. A sound reached their ears, plain and unmistakable, the rote of dashing water. "There's the surf!" rejoiced Percy. "Don't you hear it?" "_Si_, I hear it," answered Filippo. Dropping the buoy he had just gaffed, Percy took the oars and began rowing hard toward the sound, which gradually grew louder. The fog came on with a rush, sliding over them like an avalanche. It was hardly possible to see beyond the tips of the oar-blades. "Lucky we can hear that surf!" said Percy, comfortably. "But strange it sounds so loud and so near." Now it was close ahead. He stopped rowing, puzzled. A blast of cold air smote them. Suddenly there was a rushing all around. It was not the surf at all, but waves, breaking before the coming wind. They were lost in the fog! Percy faced Filippo blankly. For a moment his head went round. With bitter regret he now realized that in dropping the buoy he had given up a certainty for an uncertainty that might cost them dearly. But nothing was to be gained by yielding to discouragement. He reviewed his scanty stock of sea lore. "That wind is probably blowing from some point between northeast and southeast. If we turn around, and run straight before it, we'll be likely to hit the island." He swung the pea-pod stern to the breeze. "Here goes! Watch out sharp for lobster-buoys, Filippo!" But no buoys appeared. They might pass within ten feet of one and never see it. Five, ten, twenty, thirty minutes passed; and still no sign of Tarpaulin. The wind was becoming stronger, the waves higher; their rushing was now loud enough to drown the sound of any surf that might be breaking on the ledges of the island. Percy rowed for a quarter-hour longer, dread plucking at his heart-strings. At last he rested on his oars. "We've missed it," he acknowledged, despondently. They were lost now in good earnest. It was one o'clock. The fog hung over them like a heavy gray pall, so damp and thick that it was almost stifling. Percy turned the pea-pod bow to the wind and began rowing again. "We must try to hold our own till it clears up," he observed, with attempted cheerfulness. But his tones lacked conviction. It might not clear for two or three days. By degrees his strokes lost their force, until the oars were barely dipping. The boat was going astern fast.