A “Baby Holland” Submarine, One of the First of the U. S. N. 18
The Conning Tower and Navigating Compartment Controls of a Modern Submarine 58
The Engine Room of a Modern Submarine Showing the Diesel Engines 82
A Bliss Torpedo with Rotary Compressed Air Motor 98
A 3½ inch Submarine Gun in Action Showing the Deck Well and Manner of Operation 118
The Latest Type of Periscope. A much Magnified Image of the Object Is Shown in the Inner Circle, while in the Outer Circle Is Shown the Object Plus an “all round” View of the Horizon. A Submarine Fitted with This Periscope May well be Said to Have Eyes in the Back of its Head 136
The Crew of a Submarine (Note Sailor Going Below through Hatch in After-deck) 166
A German U-Boat “Breaking Water” Preparatory to Examining the Cargo of an Enemy ship 178
Three Eighty-Foot Gasolene Chasers on their Way to Patrol Duty 188
Navigating the “Deutschland” by Means of the Deck Control (Note Open Hatch Leading to Conning Tower) 202
THE outcome of the great war that is now being waged in Europe hinges largely on the ability of the Central Powers[1] to sink the ships of the Allies[2] by means of _submarines_, and of the Allies to destroy the enemy _U-boats_,[3] as the German submarines are commonly called.
Now, while a U-boat is a submarine, all submarines are not U-boats; for the word _submarine_ means any and everything that lives, is done, or works beneath the surface of the sea. Thus, a fish is a submarine, and so is a boy while he is under water—though his clothes may be on the shore.
=How the Submarine Came to Be.=—Yes, the fish of the _Paleozoic_[4] era, see Fig. 1, was the earliest submarine, in that it moved in and through the water under its own power, and that was millions of years before the human race and the monkey tribe branched off from a common ancestor.
[Illustration: FIG. 1. A PALEOZOIC SUBMARINE. IT WAS THE FIRST FISH TO SWIM THE WATERS OF THE EARTH.]
Not only has the shape of the fish—or _ichthyoid form_, as it is called—served as a model for inventors of the submarine boat to go by, but the air-bladder in the fish, which aids it in keeping its place below the surface of the water, finds its counterpart in the ballast tanks of the modern submarine.