A compartment tell-tale (a numbered chart showing each compartment of the boat) also hangs in sight, and if a compartment should begin to leak it is instantly indicated by the tell-tale, which in this case is a miniature electric lamp that lights up back of the number.
By pressing a button he can ring an electric bell in the leaking compartment and so warn the crew that he is about to close the electrically operated bulkhead door and so shut the compartment off from the rest of the boat if the damage done is so serious that it cannot be repaired.
Now the Navigating Compartment.—As you have read before, the conning tower is not a part of the hull but of the superstructure. Now, when the captain or any of his crew wants to get from the conning tower into the hull of the boat he must do so through a hatch in the lower deck which is exactly like the hatch in the top or bridge of the tower.
This arrangement makes it easy to shut off the conning tower into the rest of the boat if it should be seriously damaged by shell-fire or by collision. Should this happen, the boat is steered from another compartment called the navigating room, in which are all of the devices used in the conning tower. So you see there are two complete navigating rooms and an outside deck control by which the submarine can be steered and operated, no matter how badly damaged she may be.
Next, the Diving Control Compartment.—The compartment containing the diving control, by means of which the submarine can be made to dive and to come to the surface, is fitted with the following devices:
First, there is the diving wheel, which works the horizontal or diving rudders.
Next, there is the angle indicator, which is simply a quadrant—that is, a quarter of a circle—marked off into degrees and each degree into quarters. It has a needle which moves over the quadrant as the pilot turns the diving wheel and this indicates the number of degrees up or down the horizontal rudders have moved.
Another instrument is the depth indicator.
Then there is also an indicator which is merely a modified form of a carpenter’s spirit level. This little device shows when the craft is running on an even keel and when it is running with its keel inclined. For instance, should the diving rudder fail to respond to the touch of the man at the wheel, the level would indicate it, as would also the depth indicator.
Other fittings are the levers and the valve controls, by means of which water can be let into the ballast tanks.