Armament—Most navies equip their sub marines with four torpedo tubes, two on the bow and two astern; others carry an additional two in the superstructure; the latter are of fixed or revolving type. Some British sub marines have fixed port and starboard broadside tubes in the interior of the boat. The number of torpedoes carried varies from two per tube to whatever the larger space of the big ves sels permit. Both ends of the torpedo tube are covered by watertight caps or shutters each opened and closed by hand. To load a tube the inside cap is opened, leaving the outside closed and the projectile is placed in the tube, the inside cover being at once closed and the open spaces at head and tail of the cigar-shaped torpedo is filled with water by pumping or blowing water from an internal tank specially fitted for the purpose. Next the outer shutter is opened and the projectile is discharged by compressed air, released from a tank and entering behind the torpedo by electric gear operating a large valve. The boat's com mander generally performs this latter opera tion. During the torpedo's egress mechanism in the tube pulls a lever that starts the pro pelling machinery of the torpedo as it leaves the tube on its deadly mission. Another weapon of the submarine is its one or two three-inch rapid-fire used as defense against air planes, dirigibles and small craft. In submerg ing the gun is housed in the superstructure aided by its hinged mount. To render the mount more rigid the later German submarines have eliminated the hinge and on submersion leave the gun projecting, after removing the breach-block and sighting telescope. To reduce propulsion resistance when submerged the gun is enclosed in a "breakdown° casing of sheet metal. During the World War cannon have been added to armament, the calibre growing ever with the capacity of the enlarged boat. (See notice, end of article, on the very latest structures).
Periscopes and Range The eyes of the submerged craft — the periscope — in its more recently developed form consists of an arrangement of prisms within a vertical tube (see PERISCOPE) adjusted to an eye-piece simi lar to a marine telescope. Usually submarines have at least two periscopes to provide for loss, besides permitting commander and the steers man to be using one each simultaneously. The periscope tube has about six inches diameter and 18 to 20 feet length above the superstruc ture. The more recently constructed peris copes have on the upper end a reduced diameter of from two to three inches for the length of five or six feet. This has the effect of reduc ing the °periscope wave° left in its wake which makes itself more visible to the enemy than the projecting tube. The remaining instrument needful to correctly aiming the torpedo is a range-finding device; for this purpose there are several inventions, space for the description of which in this article is lacking. The dangers attendant on the operation of the submarine have given rise to numerous inventions for their prevention and cure. One of the most interesting is the keel° used in Euro pean navies; it consists of a flat, hollow keel filled with lead and has a depth of about 12 inches and about 24 inches width. This is
fastened to the hull in such a way as to permit quick releasing in emergency and the reduced tonnage quickly brings the vessel to the surface.
A good example of strictly recent submarine construction is the Holland type, United States submarine Schley, built in 1917. It is 263 feet long, displaces 1,453 tons submerged, has sur face speed of 20 knots, submerged speed 11/2 knots. The hull is divided longitudinally into nine watertight compartments. There are four torpedo tubes in the bow, two port and two starboard; water-ballast tanks are also located here for their discharge. There are also two deck torpedo tubes besides those (four) in the bow. Aft of this is the torpedo com partment. The officers' compartment comes next and the crew's quarters, with storage batteries below deck, is aft of the officers' quarters. Next comes a smaller compartment, the upper part of which contains the wireless operator's room, while the lower half is devoted to cold storage. Next, at about midlength of the vessel comes the central operating com partment with conning tower and the bridge above. The Schley has three periscopes, two running into the operating room, the third leading to the conning tower. To the rear of this is another crew's quarters and storage batteries beneath its floor. Next comes the engine-room with its two 12-cylinder engines, capable of driving the vessel at 20 knots on the surface. The next compartment contains the electric motors, one attached to each shaft, together with other auxiliary machinery. Water ballast fills the last compartment. The torpedo armament consists of four fixed tubes in the bow; and two others on a revolvable mount, which are carried above the main hull, and within the false superstructure.
During the progress of the World War wonderful stories appeared in print of the great advances being made by Germany in submarine construction and the immense size of her latest craft. The British navy had been well posted because of steady capture of enemy submarines and their consequent examination. But the officers were silent and the public was unen lightened. Captain Persius, Germany's naval critic, gave out the following figures concern ing the German submarine fleet: In 1917 Ger many built 83 and had 66 destroyed; in April of that year she had 126 submarines; in Oc tober 146. In February 1918 she had 136 and in June 113. England's 1917 War Cabinet de clared the German submarine had a surface speed of 18 and 10 or 11 knots submerged. It later). All details are not given out but we read of four of these enemy boats: °The best of these were 'tuned up) for special trial* and a special trial board appointed. The German boat tried was built at Germania Yard, Kiel, 1918, and S-3, a submarine designed by United nited States Navy Department and missioned in 1918. They both belong to the 800-ton class with the following measurements: S-3.