Nautilus

Nautilus was designed between 1793 and 1797 by the American inventor Robert Fulton, then living in the French First Republic. He twice proposed the submarine to the Directory without success — the second time offering to be paid nothing until she had actually sunk merchant shipping, and then only a small percentage of the prize money. Permission to build finally came from the Minister of Marine.

Fulton built her of copper sheets over iron ribs at the Perrier boatyard in Rouen: 21 feet 3 inches long, 6 feet 4 inches in the beam, driven by a hand-cranked screw propeller. The hollow iron keel served as her ballast tank, flooded and emptied to change buoyancy, while horizontal fins on the rudder — diving planes in modern terms — controlled the angle of dive. She carried an observation dome, a collapsible fan-shaped sail for the surface, and a snorkel of waterproofed leather.

Her weapon was what Fulton called a 'carcass' — a copper cylinder of ten to two hundred pounds of gunpowder. A device atop the dome drove a spiked eye into an enemy's wooden hull; the submarine released the mine on a line through the eye and sped away, and when the line paid out the charge struck the hull and a gunlock mechanism fired it.

The first test dives began on 29 July 1800 in the Seine at Rouen, in the Saint-Gervais dock. All were successful, but the river current interfered, so Fulton moved to the quiet salt water of Le Havre harbour. There he proved a lit candle did not strain the snorkel's air supply, and raced his two crankmen against two men rowing on the surface — over a 360-foot course, Nautilus won by two minutes.

On 3 July 1801 at Le Havre he took the revised boat down to the then-remarkable depth of 25 feet, remaining an hour with three crewmen and two candles burning. A copper globe holding 200 cubic feet of air extended the crew's endurance to at least four and a half hours, and a small glass in the dome gave light enough to read a watch. He found compasses worked underwater exactly as on the surface. The first trial of a carcass destroyed a 40-foot sloop, and the overseeing committee recommended building two 36-foot brass submarines with crews of eight.

In September 1801 Napoleon asked to see Nautilus — only to learn that, as she had leaked badly, Fulton had dismantled her and destroyed the more important parts at the end of the tests. Despite reports of success from reliable witnesses, Napoleon decided Fulton was a swindler and charlatan, and the French navy had no enthusiasm for a weapon it considered suicidal for the crews.

The British then paid Fulton £800 to cross the Channel and develop a second Nautilus — a 35-foot sea-going boat for a crew of six, provisioned for 20 days, with 30 carcass compartments and a hull disguised as a conventional sloop. The victory at Trafalgar made his work unnecessary, and he left for America in frustration in October 1806. His submarine papers, left with the American consul in London, went unpublished until 1920. Though preceded by Cornelis Drebbel's vessel of 1620 and the Turtle, Nautilus is often considered the first practical submarine.