Her method of attack was the same as the _Turtle’s_. Up through the top of the conning-tower projected what Fulton called the “Horn of the Nautilus.” This was an eyeleted spike, to be driven into the bottom of a hostile ship and left there. From a windlass carried in a water-tight forward compartment of the submarine, a thin, strong tow-rope ran through the eyehole in the spike to the trigger of a flintlock inside a copper case nearly full of gunpowder, which was not carried on deck, as on the _Turtle_, but towed some distance astern. As soon as this powder-case came to a full stop against the spike, the tow-rope would pull the trigger. Robert Fulton felt the lack of a distinctive name for such an under-water charge of explosives, till he thought of its likeness to the electric ray, that storage battery of a fish that gives a most unpleasant shock to any one touching it. So he took the first half of this creature’s scientific name: _Torpedo electricus_. Fulton had a knack for picking good names. He called his submarine the _Nautilus_ because it had a sail which it opened and folded away even as the beautiful shellfish of that name was supposed to furl and unfurl its large, sail-like membrane. On her first trial on the Seine at Paris, in May, 1801, the _Nautilus_ remained submerged for twenty minutes with Fulton and one other man on board, and a lighted candle for them to navigate by. This consumed too much air, however, so a small glass window was placed in the conning-tower, and gave light enough instead. Four men were then able to remain under for an hour. After that, Fulton made the first compressed-air tank, a copper globe containing a cubic foot of compressed air, by drawing on which the submarine’s crew could stay under for six hours. This was in the harbor of Brest, where the _Nautilus_ had been taken overland. A trial attack was made on an old bulk, which was successfully blown up. The submarine also proved its ability either to furl its sails and dive quickly out of sight, or to cruise for a considerable distance on the surface. Once it sailed for seventy miles down the English Channel. Fulton had planned a submarine campaign for scaring the British navy and merchant marine out of the narrow seas and so bringing Great Britain to her knees, more than a century before the German emperor proclaimed his famous “war zone” around the British Isles. In one of his letters to the Directory, the American inventor declared that: “The enormous commerce of England, no less than its monstrous Government, depends upon its military marine. Should some vessels of war be destroyed by means so novel, so hidden, and so incalculable, the confidence of the seamen will vanish and the fleet will be rendered useless from the moment of the first terror.” To a friend in America, Fulton wrote from Paris on November 20, 1798: