The submarine of Mr. Alstitt, constructed in 1863 at Mobile, in the U.S.A., possesses a great interest in that it was the first to be fitted with two modes of propulsion; the one for navigation on the surface, the other beneath. [Sidenote: Bourgois and Brun.] The _Plongeur_, invented by Captain Bourgois and M. Brun, and built at Rochefort in 1863, was the most ambitious attempt that had up till then been made to solve the problem of submarine navigation. It was driven by an 80 h.p. compressed-air engine, and underwent numerous trials; these did not satisfy the officials, and it was eventually converted into a water tank. The armament of the _Plongeur_ was a spar-torpedo. [Sidenote: Lacomme.] In 1869 Dr. J. A. Lacomme submitted to Napoleon III. a project for a submarine railway across the Channel. Rails were to be laid on the floor of the ocean, and in the event of an accident the submarine car, by reason of its reserve of floatability, could detach itself from the track and rise to the surface. M. Goubet has since proposed a similar “submarine ferry.” [Sidenote: Halstead.] The _Intelligent Whale_ was built at Newark in 1872 from the designs of Mr. Halstead. Its novel features were two doors in the bottom through which divers could leave the boat when submerged. On one occasion the boat went down in 16 feet of water and General Sweeney, clad in a diver’s suit, passed out through the bottom manhole, placed a torpedo under a scow anchored there for the purpose, and after entering the boat and moving away to a safe distance, exploded the torpedo by a lanyard and friction primer, and blew the scow to pieces. [Sidenote: Constantin.] During the siege of Paris, André Constantin, a lieutenant in the French navy, built a vessel which was submerged on an entirely novel principle. Instead of admitting water to sink his boat he immersed it by the drawing in of pistons working in cylinders. [Sidenote: Drzewiecki.] The Russian inventor, Drzewiecki, built a vessel at Odessa in 1877, which had two methods of submersion. Whilst in motion a system of sliding weights inclined the boat either upwards or downwards. To regain the horizontal position the weights were brought to the centre. When at rest submersion was obtained by the introduction of water into a central reservoir. [Sidenote: Campbell and Ash.]