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Submarines

 

            
             The first successful underwater craft was a leather-encased wooden rowboat, built by the Dutch Cornelis Van Drebbelin the 1620's. It carried 12 oarsmen and several passengers in a series of trips lasting several hours. It used air tubes supported on the surface of the water by floats to recycle the oxygen supply while the boat was underwater.
             The first submarine to be used in war was an egg-shaped craft, which only carried one person. The American engineer David Bushnell invented it in the 1770s. It was called "Bushnell's turtle." It was propelled by hand-operated devices, and submerged when a valve admitted water into a ballast tank, and rose when a hand pump emptied the tank. It could only remain submerged for a half-hour because it lacked an oxygen supply. It was used in an attack against a British ship during the American Revolution but failed.
             In 1800 the American inventor Robert Fulton built a submarine named the Nautilus. It was similar in shape to the modern submarine. Fulton introduced two new features in his submarine: rudders for vertical and horizontal control and compressed air as an underwater supply of oxygen. A hand-operated propeller powered the Nautilus. On the surface, sails attached to a folding mast propelled the boat.
             The American inventor John Philip Holland developed the first submarine with an efficient source of power in 1898, who used a dual-propulsion system. His submarine had a gasoline engine for surface cruising and an electric motor for underwater.
             Today submarines have many new features like a periscope, self-propelled torpedoes, sonar, radio, snorkel, and diving planes. They still use ballast tanks to submerge underwater, and they use compressed air to force the water out to surface.
             My submarine is a film canister, which has holes on the sides. It has one alka seltzer and six pennies on the inside. When it is placed in water, the weight of the pennies makes it sink, but water flows in the wholes and reacts with the alka seltzer which fills the canister with air which makes it rise.


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