"The light will be strong enough for another hour," he decided. "Have our two divers prepare to go down at once."
A launch, cleared away with the divers on board, was anchored in the middle of the oil spot. Two divers went over the side. Presently they signalled for extra cables. When these were let down they attached pieces of metal and gave the signal to haul away.
By the time that the hour was up Darrin had abundant evidence to prove that he had destroyed a mine-layer, and that his bomb had blown up several mines stored on the craft. This evidence took the form of fragments of mines.
"Some of these pieces must even have been driven up against our hull," Darrin declared. "It is a wonder that we were not sunk."
"The counter pressure of the water would lessen the force of these fragments, especially after they had been blown out through the shell of the submarine," Lieutenant Fernald argued. "But I agree with you, sir, that it's a wonder the 'Grigsby' suffered nothing worse than a shaking."
Other evidence, too, the divers sent up. The destroyed craft had surely been a mine-laying submarine. The divers measured the length of the wrecked hull, finding it to be close to three hundred feet. They reported, too, that scores of German dead lay in the wreckage.
For hours nothing more happened. Just before ten o'clock that night the mine-sweeper's blinkers signalled a call to the "Grigsby," then about four miles distant.
"They've found something," Darrin chuckled, when he reached the bridge on a call from Lieutenant Fernald.
As the "Grigsby" was heading in toward the shoal, and had some minutes still to go, Darrin asked:
"Mr. Fernald, you had a second and even more thorough inspection of the hull made, as I directed?"