Engineering Wonders of the World
Volume I

428 ENGINEERING WONDERS OF THE WORLD. of which it is built up have a thickness in the middle of the hull of ^yths of an inch, tapering to -/gths towards each end. The length over all, from nöse to point of propeller boss, is 63 feet to reduce the submarine to a “ diving ” con- dition, when the conning tower alone shows above water, all surplus buoyancy having been negatived by the addition to the ship’s weight SECTIONAL VIEW OF THE INTERIOR OF A SUBMARINE. 4 inches, the beam or diameter of the hull at its largest section 11 feet 9 inches. The sub- merged displacement, and therefore exact weight of the entire boat, is 122 tons. The pressure on a submarine’s hull, when sub- merged to a great depth, is very considerable, and to meet this external pressure the cir- cular frames to which the hull plates are riveted are set only 18 inches apart, from nose to tail. The various tanks which play so important a part in a submarine are placed under the deck and at the sides. These are (1) the “ forward ” and “ after trimming tanks ; ” (2) the “ main ballast tanks,” separated by a longitudinal bulkhead; (3) “ auxiliary bal- last tanks ; ” (4) “ gasolene tanks.” The “ trim- ming tanks ” are receptacles of relatively small capacity situated at each end of the sub- marine. Prior to diving, it is necessary to regulate the “ trim ” of the boat, and, by the careful filling or emptying of these tanks, to obtain the proper equilibrium in the longi- tudinal sense. The “ ballast tanks ” are filled of the water these tanks will hold. The boat, when thus prepared, can dive by the mere action of the horizontal rudders. In the “ surface ” condition, all superfluous water is ejected, and the vessel rides as high in the water as is possible. The difference between her surface and submerged displacement is the amount of her buoyancy. This buoyancy, the great safeguard in submersible vessels, differs very much in different types. The “ auxiliary ballast tanks ” are useful addi- tions to the main tanks to replace an absent member of the crew. They have other uses that do not need to be detailed here. The “ gasolene tanks ” contain the fuel supply for the engines. The low superstructure on the top of the hull is 31 feet 6 inches long, and 4 feet 5 inches wide. In its plates are riveted a number of cleats and rings for mooring-ropes and tow- ing-hawsers. In the front, too, a small locker or cupboard is provided for a folding anchor and its chain. This superstructure is not water-tight, wide “ scuppers ” or holes being