CHAPTER III
HOW A REAL SUBMARINE IS MADE AND WORKS
As we told you in the first chapter, there are two kinds of undersea boats. These are (1) the Holland, or submarine type, and (2) the Lake, or submersible type. Now, the Holland boat has a shape very much like a cat-fish—that is, it has a blunt round head—and hence it can dive easily; while the Lake is shaped more like an ordinary boat and has a large superstructure, as that part above the hull[16] is called, and this makes it easier for the Lake to submerge—that is, sink on an even keel.
As the art of undersea boat building moved on apace, the two kinds of craft began to lose their original distinctive features and were merged into a single type. This was done to get a boat that was as strong and as speedy as and could dive like the Holland, and to have at the same time a boat that was as fast and as seaworthy on the surface as the Lake.
This is the reason that most of the undersea craft of to-day are a cross between the two kinds. In the older boats, though, the difference is still marked; but the machinery of both is just about the same, and consequently what we shall tell you of one is just as true of the other, and from now on we shall call both kinds simply submarines.
The Parts of a Submarine.—To begin with, a submarine is formed of: (1) the hull; (2) the superstructure, which is built on the hull; (3) the steering apparatus, which includes the submerging and diving devices; (4) the power plant, which consists of the engines, the dynamo-motors, and the storage batteries, all of which drive the submarine when it is on the surface and under the water-line.
As the power plant is a most important part of the anatomy of a submarine, it will need a whole chapter to describe it the right way, and this will come next. Now I’ll start in and tell you about the other parts of the submarine.
How the Hull Is Made.—The hull is made of thin but very strong sheets of steel riveted together. As the pressure of the water on it amounts to 187 pounds to the square inch, at a depth of 300 feet, it must be well braced or else there would be the unpleasant possibility that it might be crushed in. As a rule, though, a submarine never travels at a depth much greater than 100 feet.
Now, there are really two classes of submarines: (a) those that are built for coast patrol cruising, and (b) those that are built for trans-oceanic going.