A Fessenden oscillator, before being installed. The flange of the oscillator is riveted to the shell of the ship and its diaphragm is caused to vibrate by the sound waves, which pass through water more distinctly than they do through the air. To send out signals it is caused to vibrate mechanically by electrical apparatus.
Invisible Conning Tower.—For night observation it has been proposed to use transparent conning towers built of clear glass, in which the commander takes his station and just sticks his head above the crest of the waves in order to direct his vessel against the enemy. This has not as yet come into general use because of the difficulty of securing sufficiently clear glass in the desired form. Experiments have been made, however, which show that quite a large transparent conning tower cannot be seen on a submarine at rest even when within a couple of hundred yards; the application of these conning towers will greatly increase the submarine's efficiency for night work.
Submarine Sound Receivers.—All modern submarines are fitted with devices which enable the commanders of submarines to communicate with each other when running under water even when considerable distances apart. One of these outfits consists of a signal bell and a powerful receiver with which sounds may be transmitted and heard. Conversations may be carried on by the Morse and other codes for distances of ten or twelve miles.
TORPEDO TUBES ASSEMBLED READY FOR INSTALLATION IN A SUBMARINE BOAT
Left view, the breech end of the tube. Right view, the outboard doors, which must first be opened before the torpedo is expelled from the tube by compressed air. When the torpedo is expelled it starts a compressed-air engine supplied with air stored at high pressure within the torpedo, and will run several thousand yards under its own power.
A later device, called the Fessenden oscillator, will transmit or receive sounds a distance of twenty miles. The principle of its operation is that of setting up wave vibrations by very large transmitters; these vibrations are carried by the water and taken up by receivers on other submarines. It has been found that the human voice will set up vibrations in the Fessenden transmitter so clearly that wireless conversation may be carried on under water for several hundred yards. I discovered in my earlier experiments that when a submarine was lying submerged, with all machinery shut down, the noise of the machinery in an approaching ship could be detected quite a distance off without the use of any special kind of receivers. In this way the commander of a submarine can always note the approach of an enemy simply by shutting down his own machinery. The warning thus given him comes long before he could sight the enemy ship were he on the surface. After a little experience one can tell the type of ship approaching from the sound, as every type of ship has sounds peculiar to her class. The smash of paddle wheels, the deep, slow pound of the heavy merchant ships or battleships, the clack and the whir of the higher speed machinery on destroyers or torpedo boats, are all easily recognizable when one becomes familiar with them. At the present time all the larger submarines are fitted with wireless outfits on their decks which they may use when on the surface to communicate with other submarines or with their base.
Torpedo Tubes.—These are used to start the automobile torpedo on its course toward the enemy. In simple form they are tubes about eighteen inches in diameter and seventeen feet long, placed in line with the axis of the vessel. They are fitted with doors both internal and external to the submarine. The inboard door of the tube opens into the interior of the vessel and permits the loading of the torpedo. When the torpedo is to be discharged the inboard door is closed and securely fastened. The outer door is then opened, and through the operation of quick-opening valves compressed air is admitted back of the torpedo and the torpedo is driven out of the tube in the same manner that the bullet is driven out of an air rifle or the cork out of a pop-gun. Some of the larger modern submarines carry several torpedo tubes firing in line with the axis of the vessel both forward and aft. Some carry torpedo tubes on their decks which may be made to train to fire broadside on either side of the vessel.
A WHITEHEAD TORPEDO