The _Cachalot_, which may as well be described here as elsewhere as a type of the submarine warship of the time, was a double-pointed cylinder, built of plates of nickelised aluminium steel, not riveted, but electrically fused at the joints, so that they formed a continuous mass equally impervious all over, and presenting no seams or overlaps. The cylinder was a hundred and fifty feet from point to point, with a midship’s diameter of forty feet. The forward end was armed with a sheathing of azurine, the metal peculiar to the mines of Aeria, which would cut and pierce steel as a diamond cuts glass. This sheathing formed a ram, which was by no means the least formidable portion of the warship’s armament. The upper part of the cylinder was flattened so as to form an oval deck forty feet long by fifteen wide. A centre section of this deck, three feet wide, could be opened by means of a lateral slide which allowed of the elevation of a gun twenty-five feet long, which could be used either for discharging torpedoes by water or for throwing projectiles through the air. It could be aimed and fired from below the deck without the artillerists even seeing the objects aimed at, save in an arrangement of mirrors, so adjusted that when the object appeared in the centre of the lowest of them, the gun could be fired with the certainty of the projectile reaching its mark. Four underwater torpedo tubes, two ahead and two astern, completed the armament of the submarine warship. When under water the deck could be hermetically closed, and sliding plates could be drawn over the opening of the torpedo tubes, so that from stem to stern of the cylinder there were no excrescences to impede the progress of the vessel through the water with the sole exception of a dome of thick forged glass just forward of the deck, under which stood the helmsman, who gave place to the commander of the vessel when she went into action. Her powerful four-bladed screw, driven by engines almost precisely similar to those of the air-ships, gave her a maximum speed of a hundred miles an hour. The _Cachalot_ ran at twenty-five miles an hour down the harbour, and as soon as he got abreast of Cape François Captain Ernstein, who was standing on deck, saw a small red flag apparently rising from the waves about a mile to seaward. A similar flag was soon flying from a movable flagstaff on the _Cachalot_, and a few minutes later she was lying alongside the _Narwhal_. This vessel was a very leviathan of the deep, and as she lay three parts submerged in the water Captain Ernstein calculated that she could hardly be less than two hundred feet in length and forty-five in diameter amidships. She appeared to be built on very much the same plan as the _Cachalot_ and of the same materials, saving only, of course, the ram of azurine, which was replaced by one of nickel steel.