Nautilus is often considered the first practical submarine, though preceded by Cornelius Drebbel's of 1620. The Nautilus was designed between 1793 and 1797 by the American inventor Robert Fulton, then living in the French First Republic. He proposed to the Directory that they subsidize its construction as a means to balance British seapower, but he was turned down. His second proposal to them was that he be paid nothing until the Nautilus had sunk British shipping, and then only a small percentage of the prize money. Again, rejection. He directed his next proposal, a masterpiece of logic destroying all possible objections, to the Minister of Marine, who finally granted him permission to build.
Fulton built the first Nautilus at the Perrier boatyard in Rouen of copper sheets over iron ribs. She was 21'3"/6.5 m long, 6'4" in the beam. Propulsion was a hand-cranked screw propellor. Her hollow iron keel was her ballast tank, flooded and emptied to change her buoyancy. Two horizontal fins on the stubby horizontal rudder controlled angle of dive — the origins of the diving planes used on all modern submarines. She resembled a modern research sub in shape: a long teardrop with an observation dome we would call a conning tower. When surfaced, a fan-shaped collapsible sail, looking rather Chinese, provided propulsion. At this time, air other than that enclosed was provided by a water-proofed leather snorkel tube.
She was always designed to carry a "carcass" as Fulton called his dragged mines. A device on the top of the dome drove a spiked eye into the enemy's wooden hull. The sub then released its mine on a line that went through the eye. The sub sped away, and only when the long line had paid out would the mine strike the target hull and explode by a detonator. It was nothing like a self-propelled torpedo. They were variously sized copper cylinders carrying ten to two hundred pounds of gunpowder, triggered by a gunlock mechanism that went off on contact with the hull.
Nautilus was first tested, with constant success, in dives in the Seine near Rouen beginning 29 July 1800. As the river current interfered with some tests, Fulton took the boat to Le Havre to work in the quiet salt water of the harbor. He tested endurance with a candle lit, and found the flame did not challenge the air capacity of the snorkel. He tested the speed of his two men cranking against two men rowing on the surface, and Nautilus covered the 360'/120 m course two minutes faster. During this time he changed the rudder, and the screw propellor to one with four vanes like a windmill.
Through friends like Gaspard Monge and Pierre-Simon Laplace, Fulton obtained an interview with Napoleon, but nothing came of it. However, the Minister of Marine was by Fulton's friends pushed into appointing a scholarly panel to assess the submarine, to consist of Volney, Monge, and Laplace.
On the 3rd of July, 1801 at Le Havre, Fulton took down the revised Nautilus to the then-remarkable depth of . With his three crewmen and two candles burning he remained for an hour without difficulty. Adding a copper "bomb" (globe) containing . of air extended the time underwater for the crew for at least four and a half hours. However, one of the renovations included a 1.5" d. glass in the dome, whose light he found sufficient for reading a watch, making candles during daylight activities unnecessary. Speed trials put Nautilus at two knots on the surface, and covering 400 m. in 7 minutes. He also discovered that compasses worked underwater exactly as on the surface.
The first trial of a carcass attached by the sub blew to flinders a 40' sloop provided by the Admiralty. Fulton suggested that not only should they be used against specific ships by subs, but be set floating into harbors and into estuaries with the tide to wreak havoc at random.
The overseeing committee enthusiastically recommended the building of two brass subs, 36' long, 12' wide, with a crew of eight, and air for eight hours of submersion.
In September, Napoleon expressed intereste in seeing the Nautilus, only to find that, as she had leaked badly, Fulton had her dismantled and the more important bits destroyed at the end of the tests. Despite the many reports of success by reliable witnesses like the Prefect Marine of Brest, Napoleon decided Fulton was a swindler and charlatan. The French navy had no enthusiasm for a weapon they preferred to think suicidal for the crews (though Fulton had no problems). Certainly, it would be overwhelmingly destructive for conventional ships.
Though knowing the French had no further interest, the British preferred to keep a control on this dangerous device by paying Fulton £800 to come to England (where he had been before going to France) and develop a second Nautilus for them. Once there, they concentrated him on carcasses, with which he neatly blew up the brig Dorothea off Walmer Castle in October 1805. The victory at Trafalgar made his work no longer a danger, and he was ignored until he left in a high dudgeon for America in October 1806. He left his papers on submarines with the American consul in London. He never asked for them, never referred to his Nautilus work, and the papers went unpublished until 1920.
These show that his British Nautilus was planned as a 35' long, 10' beam sea-going boat with a crew of six, to be provisioned for 20 days at sea. The upper surface was provided with 30 carcass compartments. The hull was to imitate a sea-going sloop with conventional-looking mast and sails that could be lowered and unstepped for submersion. Her 2-bladed propellor, still hand-cranked, folded up out of the water when surfaced to reduce drag. When submerged, air came through two streamlined ventilation pipes, and light from the conning tower. However, nothing of it was actually constructed.