At full speed, too, Dave tried for the second hidden enemy boat. There was barely time to have the second bomb in place when signal and order came.
Another terrific explosion, like that of the afternoon! It seemed as though the waters must divide! Yet the "Grigsby," moving fast all the time, felt the shock severely, but not like the one of the afternoon.
About the destroyer came, playing her searchlight on the waters. The tell-tale oil patches were there, showing only too plainly that two submarine craft had been destroyed.
"Apparently one craft carried no mines, while the other was loaded with them," said Dave to his executive officer. "Fernald, I think I'm beginning to get an idea of the way the enemy are working their mine-laying game. If I'm right we'll make a record along this patch of shoals while the hunting lasts."
Patiently Fernald listened and waited, but did not speak. He hoped to hear what his chief's idea was, but it was not the executive officer's place to ask for it.
"I may even be able to figure out when the best time would be for hunting these lazy rascals resting on the bottom," Darrin continued.
Mr. Fernald began to show signs of a more active curiosity.
"But I won't say much about it," Darrin smiled, "until I've more data to work on and have proved some part of my theory."
Lieutenant Fernald looked so much like a man who wished to speak that Dave laughed.
"Out with it, Fernald," he urged good-humoredly. "You've an idea, too. You may tell me if you wish."