"It's a fog coming up!" he said uneasily, for that was the one thing he
had dreaded most of all while out upon the open waters of the big gulf,
and no haven near at hand.

With incredible swiftness the blanket seemed to sweep over the surface of
the sea. In ten minutes they were completely surrounded, and could not
discern any object fifty feet away.

"This is awkward, fellows; but perhaps it may not last long. Meanwhile,
we will have to steer by the compass. All of you listen to hear the wash
of the rollers on the beach, if we happen to get in too close," said
Frank, trying to keep calm.

They continued along for half an hour, under reduced speed. Still the fog
remained as dense as ever. Frank was wondering if they might not pass the
first haven without knowing it. He thought it was very unfortunate that
such a thing as this should occur on their very first day out.

"Hello! What are you stopping for?" demanded Jerry suddenly, as the sound
of the bustling little motor ceased and the boat slowed down.

Frank was bending low over the machinery.

"I don't know, fellows, but something has happened to the motor. That
stop was none of my doing; but I hope it won't amount to much," he
said cheerfully.

The other three looked at each other uneasily. With the motor broken
down, and surrounded by a treacherous fog, out there on the big gulf,