Robert Fulton, probably the greatest genius in nautical invention, carried the development of bath mines and submarines much further. His _Nautilus_, so-called because its collapsible sail resembled that of the familiar chambered nautilus, was surprisingly ahead of its time; it had a fish-like shape, screw propulsion (by a two-man hand winch), horizontal diving rudder, compressed air tank, water tank filled or emptied by a pump, and a torpedo[1] consisting of a detachable case of gunpowder. A lanyard ran from the torpedo through an eye in a spike, to be driven in the enemy hull, and thence to the submarine, which as it moved away brought the torpedo up taut against the spike and caused its explosion. Fulton interested Napoleon in his project, submerged frequently for an hour or more, and blew up a hulk in Brest harbor. But the greybeards in the French navy frowned on these novel methods, declaring them "immoral" and "contrary to the laws of war." [Footnote 1: This name, coined by Fulton, was from the _torpedo electricus_, or cramp fish, which kills its victim by electric shock.] [Illustration: BUSHNELL'S TURTLE] Later the British Government entered into negotiations with the inventor, and in October, 1804, used his mines in an unsuccessful attack an the French flotilla of invasion at Boulogne. Only one pinnace was sunk. Fulton still maintained that he could "sweep all military marines off the ocean."[2] But Trafalgar ended his chances. As the old Admiral Earl St. Vincent remarked, "Pitt [the Prime Minister] would be the greatest fool that ever existed to encourage a mode of war which they who command the sea do not want and which if successful would deprive them of it." So Fulton took L15,000 and dropped his schemes. [Footnote 2: Letter to Pitt, Jan. 6, 1806.] [Illustration: FULTON'S NAUTILUS] Much cruder than the _Nautilus_, owing to their hurried construction, were the Confederate "Davids" of the Civil War. One of these launches, which ran only semi-submerged, drove a spar torpedo against the U. S. S. _New Ironsides_ off Charleston, but it exploded on the rebound, too far away. The C. S. S. _Hunley_ was a real submarine, and went down readily, but on five occasions it failed to emerge properly, and drowned in these experiments about 35 men. In August, 1864, running on the surface, it sank by torpedo the U. S. Corvette _Housatonic_ off Charleston, but went down in the suction of the larger vessel, carrying to death its last heroic crew.