The first submarine built for the French navy was the _Gymnote_. The original plans of this vessel were worked out by the celebrated engineer, Dupuy de Lôme, but unfortunately he never lived to execute his project, for he died just when he had finished the details. Some years later M. Gustave Zédé, a Marine Engineer, revived the ideas of his friend, and after making some modifications in Dupuy de Lôme’s original design, he brought it before Admiral Aube, the Minister of Marine, who accepted it at once, and signed a contract for its construction by the Société des Forges et Chantiers de la Méditerranée. M. Zédé was one of the directors of this society, and thus he was able to superintend the work, which was carried out under the direction of M. Romazzotti, then first-class Assistant Engineer of Marine. The _Gymnote_ is built of steel in the shape of a cigar. It is 59 feet long, 5·9 feet beam, and 6 feet in diameter, just deep enough to allow a man to stand upright in the interior; its displacement is 30 tons, a total weight a little less than the weight of the water displaced by the boat when completely immersed, and its speed about 6 knots; leaden plates placed on each side of the boat in two hollows regulate its draught of water. The top of the vessel affords a narrow platform, and on this are a manhole and a little cupola, with windows. The motive power was originally an electro-motor of 55 h.p., driven from 564 accumulators. It was designed by Captain Krebs and built in the workshops of the Société des Forges et Chantiers at Havre. It was of extraordinary lightness, weighing only 4,410 lbs., and drove the screw at the rate of 2,000 revolutions a minute, giving a speed of 6 knots an hour, its radius of action at this speed being 35 knots; reduced to 4 knots its radius of action was 100 miles. This motor was afterwards replaced by a much simpler machine. Immersion is obtained by the introduction of water into three reservoirs, placed one forward, one aft, and one centre. The water is expelled either by means of compressed air or by a rotary Behrens pump worked by an electro-motor. Two horizontal rudders steer the boat in the vertical plane and an ordinary rudder steers it on the horizontal. Originally one horizontal rudder only was carried at the stern, but this did not answer well and was given up.