tower—a room glassed on four sides like the lantern room of a lighthouse, and provided with telescope, a telephone switchboard, range finders, and all the complicated machinery of gunfire control. On one side were trestle boards supporting charts of the ranges—figured areas representing every square yard of water from the nearer harbor below out to the farthest reaching distance of the monster disappearing guns. A second graphic sheet showed the harbor and anchorages and the entrance to the straits; this map was thickly spotted with little, red, numbered dots—the mines. Sown like a turnip field with these deadly capsules of destruction were all the waters thereabouts; their delicate tendrils led under water and through conduits in the Rock up to this slender spire called the signal tower. As he climbed the winding stairway to his newly assigned post, Woodhouse had seen painted on a small wooden door just below the room he was to occupy the single white letter "D."
Room D—where the switches were, where a single sweep of the hand could loose all the hidden death out there in the crowded harbor—it lay directly below his feet.
