March glanced around him quickly. And despite the number of drawings and pictures he had seen of the control room of a submarine, he gasped. Never had he seen such a myriad of instruments and wheels and levers and dials! Everything in the entire submarine was really controlled from this one central room. Beside him, in the middle of the room, were the two thick steel shafts which he knew were the periscopes. Their lower ends were down in wells in the deck and would not be raised until after they were submerged and the skipper wanted to look around. Facing the bow of the ship, March saw the forward bulkhead of the control room. Yes, there was the huge steering wheel with the helmsman holding it lightly. It seemed strange for a helmsman to be looking at a wall, or instrument panels on a wall, rather than at the open sea over which he steered. March knew that the controls were electrically operated by the wheel and thus easy to handle. But every man was made to steer it by hand on occasion—and that took real strength!—in order to be ready for that emergency that might come when the electric current failed. Forward, also, were the wheels controlling the angles of the diving planes. There was the gyro-compass dial, and near by the little table at which the navigation officer sat. “Some day that’s where I’ll be,” March said to himself. He didn’t have time to look carefully at the many other dials against this wall, but he knew they showed the ship’s depth under water, the pressure, and other essential data. Along the sides were still more dials showing the amount of fuel in tanks, the number of revolutions per minute being made by the propellers. He recognized the inclinometer, which showed just exactly the angle of tip assumed by the boat in diving or coming up. On another side were the long levers and wheels controlling the big Kingston valves which flooded the ballast tanks with sea water when the ship was to dive, the air vents, the pumps, and other equipment used in diving and surfacing. The regular crew stood tensely at their posts without a word, and the students who stood near by were completely silent. March glanced at the Skipper and saw that he was looking at a huge panel on one wall. Yes, this was the “Christmas Tree!” It was a large electric indicator board covered with red and green lights. It showed the exact condition of every opening—hatches, air induction vents, and all—into the ship. Everything having anything to do with diving had its indicator there on the board. March saw that most of the lights were green, but many were still red. He knew that every light had to be green before the ship could dive. “Stand by for diving,” said the Skipper in a quiet voice.