Electricity was first applied in 1861 by another Frenchman, named Olivier Riou. This is the ideal motive-power for underwater boats, and it was at this time that Jules Verne described the ideal submarine in his immortal story of “Twenty Thousand Leagues Under the Sea.” But before we can have a _Nautilus_ like Captain Nemo’s we must discover an electric storage battery of unheard-of lightness and capacity. [Illustration: _Le Plongeur._] There was a great revival of French interest in electric submarines after Admiral Aube, who was a lifelong submarine “fan,” became minister of marine in 1886. In spite of much ridicule and opposition, he authorized the construction of a small experimental vessel of this type called the _Gymnote_. She was a wild little thing that did everything short of turning somersaults when she dived, but she was enough of a success to be followed by a larger craft named, after the great engineer who had designed her predecessor, the _Gustave Zédé_. “The history of the _Gustave Zédé_ shows how much in earnest the French were in the matter of submarines. When she was first launched she was a failure in almost every respect, and it was only after some years, during which many alterations and improvements were carried out, that she became a serviceable craft. At first nothing would induce the _Gustave Zédé_ to quit the surface, and when at last she did plunge she did it so effectually that she went down to the bottom in 10 fathoms of water at an angle of 30 degrees. The committee of engineers were on board at the time, and it speaks well for their patriotism that they did not as a result of their unpleasant experience condemn the _Gustave Zédé_ and advise the government to spend no more money on submarine craft.”[10] Twenty-nine other electric submarines were built for the French navy between 1886 and 1901. During the same period, a French gentleman named M. Goubet built and experimented with two very small electric submarines, each of which was manned by two men, who sat back to back on a sort of settee stuffed with machinery. Little or big, all these French boats had the same fatal defect: lack of power. Their storage batteries, called on to propel them above, as well as below, the surface, became exhausted after a few hours’ cruising. They were as useless for practical naval warfare as an electric run-about would be to haul guns or carry supplies in Flanders. But if compressed-air and electricity were too quickly exhausted, gasoline or petroleum was even less practicable for submarine navigation. To set an oil-engine, that derives its power from the explosion of a mixture of oil-vapor and air, at work in a small closed space like the interior of a submarine, would soon make it uninhabitable. While Mr. Holland was puzzling how to overcome this difficulty, in the middle eighties, a Swedish inventor named Nordenfeldt was building submarines to be run by steam-power.