This experience caused me to apply to the _Argonaut_ a further improvement, for which I had already applied for a patent. This was to build around the usual pressure-resisting body of a submarine a ship-shape form of light plating which would give greater seaworthiness, better lines for surface speed, and make the vessel more habitable for surface navigation. It would, in other words, make a "sea-going submarine," which the usual form of cigar-shaped vessel was not, as it did not have sufficient surface buoyancy to enable it to rise with the seas, and the seas would sweep over it as they would sweep over a partly submerged rock. [Illustration: THE "ARGONAUT," AFTER BEING LENGTHENED AND REBUILT, IN 1898, SHOWING SHIP-SHAPED, WATERTIGHT, BUOYANT SUPERSTRUCTURE] The _Argonaut_ was therefore taken to Brooklyn, twenty feet added to her length, and a light, watertight, buoyant superstructure of ship-shape form added. This superstructure was opened to the sea when it was desired to submerge the vessel, and water was permitted to enter the space between the light plating of the ship-shape form and the heavy plating of the pressure-resisting hull. This equalized the pressure on the light plates and prevented their becoming deformed, due to pressure. The superstructure increased her reserve of buoyancy in the surface cruising condition from about ten per cent. to over forty per cent., and she would rise to the seas like any ordinary type of surface vessel, instead of being buried by them in rough weather. This feature of construction has been adopted by the Germans, Italians, Russians, and in all the latest types of French boats. It is the principal feature which distinguishes them in their surface appearance from the earlier cigar-shaped boats of the diving type. This ship-shape form of hull is only suited to level-keel submergence, and must be controlled by hydroplanes. I also departed from the cigar-shaped inner hull and was granted a patent on a form of pressure-resisting hull with rising axes. This improvement overcame the tendency to dive by the head common to the cigar-shaped form, increased the surface speed on an equivalent displacement, and gave a considerable increase in metacentric height over a vessel of equivalent length and beam. Some incorrectly informed writers of books and magazines have, through their lack of complete information, given the credit of inventing and developing this seagoing type of submersible to the Krupps of Germany, to former Naval Constructor Lauboeuf, of France, or to former Naval Constructor Laurenti, of Italy. For the purpose of giving a correct history of this development, perhaps I may be pardoned and not considered overconceited if I mention a few facts in connection with the development of this type of boat in European countries. On April 2, 1897, I applied for a patent on a combined surface and submarine vessel, the specifications of which began as follows: