The Good Shepherd

by C.S. Forester

The point where the U-boat had dived was known; she could be proceeding outwards from that point at two knots, four knots, eight knots. In the plot down below circles would be drawn spreading out from that point like ripples round the spot where a stone drops into a pond. The U-boat would be known to be within the largest circle. In ten minutes she could travel a mile easily, and a circle with a radius of a mile would be over three square miles in area. To search three square miles thoroughly would take an hour, and in an hour the maximum circle would expand to enclose a hundred square miles. It was most unlikely that the U-boat would linger near the point where she dived. She would head somewhere, in some direction, along one of the three hundred and sixty degrees radiating out from her center. Yet it seemed the most reasonable assumption that below the surface she would continue the course she had been following on the surface. Even a German submarine, cruising in the North Atlantic in search of prey, did not wander about entirely aimlessly. She would make a wide sweep in one direction and then a wide sweep in another. If she had dived for some trivial reason she would probably maintain her course; if she had dived to attack the convoy she would probably maintain her course, too, seeing that was the course that would bring her square into its path. If she was on any other course it would be hopeless to seek her with a single ship; hopeless, that was the right word, not d...