The wooded bluffs of Tarpaulin had disappeared. While they had been wrestling with the stubborn trap the fog had stolen a march on them. On all sides loomed a horizon of gray mist, not a half-mile distant and steadily drawing nearer. They must locate the island and get back to it at once.
Percy tossed over the buoy and the warp at which they had been pulling. Tarpaulin lay southwest; but which way was southwest? Busied with the trap, he had utterly lost all sense of direction. The sun? He glanced hopefully up. No; that would not help any. The fog was too dense. Ha! The surf?
"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."