“It can be steered to the surface by the diving rudders, or sent flying to the top through emptying the storage tanks. If it strikes bottom, or gets stuck in the mud, it can blow itself loose by means of its compressed air. It cannot be sunk unless pierced above the flooring. It has a speed capacity of from eight to ten knots either on the surface or under water. “It can go 1500 miles on the surface without renewing its supply of gasolene. It can go fully forty knots under water without coming to the surface, and there is enough compressed air in the tanks to supply a crew with fresh air for thirty hours, if the air is not used for any other purpose, such as emptying the submerging tanks. It can dive to a depth of twenty feet in eight seconds. “The interior is simply packed with machinery. As you climb down the turret you are confronted with it at once. There is a diminutive compass which must be avoided carefully by the feet. A pressure gauge is directly in front of the operator’s eye as he stands in position. There are speaking-tubes to various parts of the boat, and a signal-bell to the engine-room. “As the operator’s hands hang by his sides, he touches a wheel on the port side, by turning which he steers the little vessel, and one on the starboard side, by turning which he controls the diving machinery. After the top is clamped down the operator can look out through plate-glass windows, about one inch wide and three inches long, which encircle the turret. “So long as the boat is running on the surface these are valuable, giving a complete view of the surroundings if the water is smooth. After the boat goes beneath the surface, these windows are useless; it is impossible to see through the water. Steering must be done by compass; until recently considered an impossible task in a submarine boat. A tiny electric light in the turret shows the operator the direction in which he is going, and reveals the markings on the depth gauges. If the boat should pass under an object, such as a ship, a perceptible shadow would be noticed through the deadlights, but that is all. The ability to see fishes swimming about in the water is a pleasant fiction. “The only clear space in the body of the boat is directly in front of the bench on which the man in the turret is standing. It is where the eighteen-inch torpedo-tube, and the eight and five-eighths inch aërial gun are loaded. “Along the sides of this open space are six compressed-air tanks, containing thirty cubic feet of air at a pressure of 2000 lbs. to a square inch. Near by is a smaller tank, containing three cubic feet of air at a fifty pounds pressure. A still smaller tank contains two cubic feet of air at a ten pounds pressure. These smaller tanks supply the compressed air which, with the smokeless powder, is used in discharging the projectiles from the boat.