I looked into the eyepiece, which was so much like that of an old-fashioned stereoscope that I felt that it, too, ought to work back and forth after the manner of a slide trombone. I found myself looking out over the broad blue waters of a sunlit bay. I noticed a squall blackening the surface of the water, a catboat running before it, and the gleam of the brass instruments of the band playing on the after deck of a big white excursion steamer half a mile away. “I can almost imagine I can hear the music of that band,” I exclaimed. “The optical illusion is perfect.” “It has to be,” rejoined the lieutenant. “If the image were in the least distorted or out of perspective, we couldn’t aim straight.” “What do you do when the periscope is wet with spray?” I asked him. “Wash the glass with a jet of alcohol and dry it from the inside with a current of warm air passing up and down the tube. A periscope-tube is double: the outer one passing through a stuffing-box in the hull, and the inner tube revolving inside it. The old-fashioned single tubes were too hard to revolve and the resistance of the water used to bend them aft and cause leakage. We can raise and lower the periscopes at will, and all our larger boats have two of them, so that they can keep a lookout in two directions at once, besides having a spare eye in case the first is put out.” “What are those two little things that big naval tug is towing over there?” I inquired. “The target for our torpedo practice,” replied Lieutenant Scope. “We shall try to put four Whiteheads between those two buoys as the tug tows them past at an unknown range and speed. If you step forward to the torpedo room you can see them loading the tubes.” As I walked forward it occurred to me that the twenty-odd men on board the _X-4_ seemed to be moving about inside her with perfect freedom, without disturbing her trim. I mentioned this to one of the crew. [Illustration: Courtesy of the Electric Boat Company. Forward torpedo-compartment, U. S. Submarine, showing breech-mechanism of four tubes. Round opening above is the escape-hatch. ] “It’s the trimming-tanks that keep her level,” he explained. “As we’re walking forward, our weight in water is being automatically pumped from the trimming-tank in the bow to the one astern. A submarine is just one blamed tank after another. Stand clear of that chain-fall, sir; they’re loading No. 1 tube.” Stripped to the waist like an old-time gun-crew, four beautifully muscled young gunner’s mates were hoisting, with an ingenious arrangement of chains and pulleys, a torpedo from the magazine. The breach of the tube was opened and the long Whitehead thrust in, two flanges on its sides being fitted into deep grooves in the sides of the tube, so that the torpedo would not spin like a rifle-bullet but be launched on an even keel. The breach was closed, and the men stood by expectantly.