Suddenly a loud whistling noise rent the air, its weird shriek outvoicing the roar of the motor.
"Down helm!" shouted Mr. Graham.
Findlay, who had relieved the Patrol Leader at the helm, put the tiller hard over. Even as he did so, a faint light appeared through the fog almost on top of the yacht. Then the crew had a brief glimpse of a large can-buoy, painted in black-and-white vertical stripes, as it swept past them, straining at its moorings in the strong tideway.
It was a narrow squeak. A few feet nearer and the Spindrift would have crashed violently into the buoy. Even her stout planks and heavy timbers could not have withstood the shock.
Five seconds later the buoy was lost in the mist, but as a parting reminder it emitted another long-drawn whistle.
"It's the Run-something Buoy, sir," said Desmond. "I saw the first three letters painted on the side."
"Runnelstone," said Mr. Graham. "It marks a dangerous rock off the coast. Fortunately, we were outside the buoy. Put her east-sou'-east, Jock."
Mr. Graham realized that there was something wrong. Although he had allowed, as he thought, ample margin, the original course was not sufficient to give the coast a wide enough berth. Either the compass was in error, or else a strong indraught of tide was setting the yacht ashore. By steering another point to the south'ard the Spindrift ought to be clear of everything.
Hour after hour passed in nervous tension. All the crew kept on deck, straining their eyes needlessly, and listening for the faintest sound. In spite of oilskins, they were wet through. The fog, cold and clammy, seemed to penetrate everything. At one time, the fog-horns and wrens of several craft were distinctly audible. At another a bell clanged dolorously. But for the most part the yacht was in a zone of silence, broken only by the noise of the engine and the sullen splash of the water against her bows.
"Switch off the motor, Jock," said the Scoutmaster. "We haven't any too much petrol, and we may want the engine to help us into port."