What the Nautilus accomplished. The British design compared with that of the Nautilus. Folding propeller. Horizontal propeller. Details of machinery. Effectiveness of the vessel. Screening the Channel. However interesting from an academic point of view may be Fulton’s views on philosophy, free trade and social problems, and his personal peculiarities as displayed in his negotiations with government officials, the animating question of historical bearing relates to the boat itself. Was the design practical, would it as developed have been able to serve a useful purpose, or was it only a single step in a long process of evolution? The Nautilus, defective as she was in many particulars which Fulton admitted, clearly demonstrated certain facts: firstly, that a boat could be made to plunge and rise at will; secondly, that it could remain under water with a crew of three men for several hours; thirdly, that it could be manoeuvered and steered by the compass under water as well as on the surface. These features are the essence of the principle of successful submarine practice, and so much Fulton accomplished. It is a far cry from a little vessel like the Nautilus, no bigger than a ship’s boat that is carried at the davits, to a modern submarine capable of keeping the seas for many weeks, of crossing and recrossing the ocean without replenishing either stores or fuel, and of carrying not only torpedoes and apparatus for their discharge but also a 12–inch long-range gun firing a projectile weighing nearly one-half ton. Except as to size, which is not really a basic feature of principle, the modern submarine differs from Fulton’s proposals in that it possesses an engine actuated when on the surface by a fuel (oil) whose activity can be instantly stopped preparatory to plunging, and by a power (electric storage battery) that neither generates heat nor vitiates the air while submerged. For that combination of motive power the world had to wait another hundred years. The Nautilus, as a matter of fact, was something vastly more than a toy or experimental model. It possessed real offensive powers, and a fleet of them, as Fulton proposed and as the British navy officials feared, would have been able to do real havoc. In estimating the offensive power of Fulton’s design, the picture of the modern submarine must be kept out of sight. The latter is called on to meet conditions of mechanical development and types of hostile vessels that are as much in advance of those existing when Fulton lived, as is the complicated mechanism of a present-day submarine over the hand-driven propeller proposed by him.