The history of invention has no chapter more interesting than that of sailing under the ocean’s waves. The navigation of the air approaches it in character, but does not present the vital problems of undersea travel. Both these new fields of navigation have been notably developed within recent years, largely as a result of the great European war. It is the story of sailing in the depths beneath the ocean’s surface with which we here propose to deal. The problem was settled easily enough for his purpose by Jules Verne, in his “Twenty Thousand Leagues Under the Sea.” But that was pure fiction without scientific value. It is with fact, not fiction, that we are here concerned. [Illustration: A SUBMARINE ABOUT TO SUBMERGE] The story takes us back three hundred years, to the reign of James I, of England, when a crude submarine boat was built, to be moved by oars, but one of no value other than as a curiosity. At a later date a man named Day built a similar boat, wagering that he would go down one hundred yards and remain there twenty-four hours. So far as is known, he still remains there, winning the wager which he has not come up to claim. Other such boats were constructed at intervals, but the first undersea boat of any historical importance was the “American Turtle,” built by a Yankee named David Bushnell during the time that the British held New York in the Revolutionary War. He sought to blow up the British frigate “Eagle” with the aid of a torpedo and nearly succeeded in doing so, seriously scaring the British shippers by the explosion of his torpedo. The next to become active in this line of discovery was Robert Fulton, the inventor of the first practical steamboat. He, like Bushnell, was an American, but his early experiments were in France, where Napoleon patronized him. With his boat, the “Nautilus,” he made numerous descents, going down twenty-five feet in the harbor of Brest and remaining there an hour. He said that he could build a submarine that could swim under the water and destroy any war vessel afloat. But the French Admiralty refused to sustain him, one old admiral saying, “Thank God, France still fights her battles on the surface, not beneath it.” Fulton finally went to England and there built a boat with which he attached a torpedo to a condemned brig, set aside for that purpose. The brig was blown up in the presence of an immense throng, and Fulton finally sold his invention to the British government for $75,000. Nothing further came of it. The submarine next came into practical view during the American Civil War, when the Confederate government built several such vessels, known usually as “Davids” from their inventor. Now, for the first time, did such a craft demonstrate its powers. On the night of February 17, 1864, one of the “Davids,” the “Hunley,” blew up the steamship “Housatonic” in Charleston harbor. The wave caused by the explosion swamped the submarine and it and its crew found a watery grave.