The periscope is the eye of the submarine. It allows observation of the sea and the sky above, while the submarine remains submerged. It is also a crucial piece of combat equipment, featuring a stadimeter to estimate the range and course angle of a target. Originally printed by the U.S. Navy, this Periscope Manual explains the operation and design of the periscope, and includes descriptions of its complex optical and mechanical details. It also contains maintenance and repair information. It s a wonderful reference for anyone interested in the science of optics, for the modeler or museum docent, or anyone who ever wondered, How the heck does that work?