The parts indicated by numbers in this illustration are as follows: 1, main ballast tanks; 2, fuel tanks; 3, keel; 4, safety drop keel; 5, habitable superstructure; 6, escape and safety chambers; 7, disappearing anti-aircraft guns; 8, rapid-fire gun; 9, torpedo tubes; 10 torpedoes; 11, twin deck torpedo tubes; 12, torpedo firing tank; 13, anchor; 14, periscopes; 15, wireless; 16, crew's quarters; 17, officers' quarters; 18, warhead stowage; 19, torpedo hatch; 20, diving chamber; 21, electric storage battery; 22, galley; 23, steering gear; 24, binnacle; 25, searchlight; 26, conning tower; 27, diving station; 28, control tank; 29, compressed-air flasks; 30, forward engine room and engines; 31, after engine room and engines; 32, central control compartment; 33, torpedo room; 34, electric motor room; 35, switchboard; 36, ballast pump; 37, auxiliary machinery room; 38, hydroplane; 39, vertical rudders; 40, signal masts.] =How the Submarine Works.=--Reference to the diagrammatic view of a modern submarine will probably make clear the following explanation of the operation of a submarine. We will assume that our submarine leaves her own harbor with fuel, stores, and torpedoes on board, wireless and signal masts erected. She is bound to a station farther down the coast, but receives word by wireless that an enemy fleet has been seen approaching the coast in such a direction as to indicate an attack on New York. She receives instructions to return and take up a station fifteen miles off Sandy Hook, the entrance to New York Harbor, and also that she is to coöperate with the smaller harbor-defense submarines that are permanently located in New York. She therefore puts back to the station designated. All deck fittings and lines are stowed except the ventilators and the deck wireless outfit; the latter is left standing so as to keep in touch with the scout ships and destroyers which are reporting the approach of the enemy. Shortly after arriving at her station, the commander notes smoke on the horizon and orders are given to "prepare to submerge." Each member of the crew then proceeds to his particular task; the wireless masts and ventilators are quickly housed, and all hatches are closed and secured. The quartermaster and submerged-control man who controls the steering and hydroplane operating gear take their stations in the control department. The engines are uncoupled by means of the rapid operating clutch, the electric motor is coupled, the hydroplanes are unfolded, the valves are opened, and the word is passed to the commander, "All ready for submergence!" All this is done in a modern vessel in less than two minutes.