Mr. Lake then sent the _Argonaut_ to a Brooklyn shipyard, where her original cigar-shaped hull was cut in half, and lengthened twenty feet, after which a light ship-shaped superstructure was built over her low sloping topsides. To keep it from being crushed in by water pressure when submerged, scupper-like openings were cut in the thin plating where it joined the stout, pressure-resisting hull, so that the superstructure automatically filled itself with sea-water on submerging and drained itself on rising again. Though uninhabitable, its interior supplied useful storage space, particularly for the gasoline fuel tanks, which, as Mr. Lake had already discovered, gave off fumes that soon rendered the air inside the submarine unbreathable, unless the tanks were kept outside instead of inside the hull. The swan-bow and long bowsprit of the new superstructure, together with the two ventilator-masts, gave the rebuilt _Argonaut_ a schooner-like appearance, and her bowsprit has been compared to the whip-socket on the dashboard of the earliest automobiles. But Mr. Lake declares that this was no useless leftover but a practicable spring-buffer to guard against running into submerged rocks, while the bobstay helped the _Argonaut_ to climb over the obstruction, as she could over anything on the sea-bottom she could get her bows over. Primarily, the superstructure served to make the submarine more seaworthy as a surface craft. Until then, most inventors and designers of undersea boats had confined their attentions to the problems of underwater navigation only, because, as had been pointed out by the monk Mersenne before 1648, even during the most violent storms the disturbance is felt but a little distance below the surface. But Mr. Lake realized that a submarine, like every other kind of boat, spends most of its existence on top of the water and that it is not always desirable to submerge whenever a moderate-sized wave sweeps over one of the old-fashioned, low-lying, cigar-shaped vessels. With her new superstructure, the _Argonaut_ rode the waves as lightly as any yacht and ushered in the era of the sea-going submarine.