Submarine! It’s a word that’s in everybody’s mind—on every one’s tongue.

The very sound of it conjures up thoughts of great ships that were and will be torpedoed and sent to the bottom of the old ocean to rust and to rot there.

Of all the mighty monsters that ever sailed the seven seas this piratical craft is by long odds the most daring as well as the most dangerous to both life and property.

And yet while of course you know that a submarine can travel on or under the water, dive like a porpoise and destroy an enemy ship by shooting a torpedo at her, do you know exactly how an undersea boat works and fights and just how she does all the seemingly impossible feats for which she is notorious?

At the present time the greatest war in the world’s history is being fought, and you are more than a mere looker-on for your country is in it and you may be one of the boys who will be called to the colors to defend her on, or against, these undersea craft.

If for no other reason than this you ought to follow not only the battles as they are being fought on the east and west fronts of Europe, but the warfare that is being waged by the submarines on the high seas, for on these boats hinges to a very large extent the outcome of the war.

Ever since the year of 1900 when five of the first really successful submarines were built in the United States and sent to England the value of this kind of war-craft has gone forward by leaps and bounds as the devices for operating them were more and more improved.

Further too the submarine has played a far larger part in the war that is now going on than the wildest fancies of her inventors of twenty years ago could have pictured, much less believed, and what is of even greater import she bids fair to become the champion fighter of the sea in the future.

Indeed so wonderful is the submarine and so great are her possibilities that you should by all means know exactly how she is made and works, as well as her torpedoes. The easiest and certainly the most interesting way to find out these things is to read this book and then build a model submarine and torpedo according to the simple directions we have given.

To open the covers of this book and to read it is the next thing to going through the hatch in the bridge of the conning tower and examining the mechanism at first hand. So do it now.