Then the submarine settled down to a rushing sixteen-knot gait." "I didn't know, sir," ventured Farley, "that submarines could go quite so fast." "The old types didn't," Lieutenant Jack answered.

"However, on the surface a capable submarine must be able to show a good deal of speed." "For getting away, sir ?" "Oh, no.

Naturally, when a submarine is pursued she can drop under the surface and leave no trail.

But suppose a single submarine to be guarding a harbor, unaided by other fighting craft.

A twenty-or twenty-two knot battleship is discovered, trying to make the harbor.
Even if the battleship steams away the submarine should be capable of following.