“He’ll know we’re closing in to cover him with our hydrophones,” said Evans, “and assuming that, his best chance to get out of range is either to hold the course he’s been on, nearly at right angles to ours, or to double back about at right angles the other way.”
“I wonder which he’ll do.”
“I bet he’ll go back,” said Evans.
“He’s about as likely to think we’ll expect him to, and keep right on.”
“They don’t think much of our intelligence,” said Evans. “Of course it’s a gamble; but I bet he thinks we’re too stupid to think of his doubling back; he’ll bet on our going for the place his course has been taking him.”
“Well,” said Fraser, “suppose he hears us when we’re fifteen miles off, and then submerges and changes course. His best speed submerged is nine knots. By the times we get there he may be anywhere within a radius of about four miles of that point. The farthest we can hope to hear with our hydrophones, while we’re going faster than he, is a mile. That means we can cover at best a strip six miles wide. We’ve got to leave two miles of the circle uncovered on the first shot. If we miss, we can double back. If he goes slow enough, we’re apt to miss him altogether. I guess it’s our wits against his, with a betting element thrown in. Anyhow, I’m not betting on him to-night.”
Twenty-five minutes of converging courses brought the wing ships within two miles of the flagship, and dimly their dark forms and white streaming wakes could be seen through the darkness on either side. Now the assumed spot where the submarine, hearing her pursuers, had probably submerged, lay seven miles dead ahead;—twelve minutes more at their racehorse speed.
Fraser spoke. “Evans, I’ll chance it on your guess, and cover the eastern half of the circle, leaving the western two miles to search later if we miss.”
A few brief words were flashed out by radio phone, and the next minute the squadron had changed course eight degrees to the eastward, and all three charged on at top speed.
Presently the executive officer said, “Isn’t it about time to slow down and give the listeners a chance, Cap’n? They can’t hear anything while we go at this speed.”