We walked around her; Dr. Plantet showed her points with a creator’s pride. Hardly a projection to mar this sleek exterior. The vertical and horizontal rudders might have been a tail; the lateral planes, flexible, sensitive as the wing-tips of a wasp-flyer, were folded in against the hull, so closely that the cracks of them were barely visible. A workman on board slid them out for us--fins opening out to barely a foot of width, trembling in the air like thin steel sheets. There were tiny stern ports for the atomic exhausts; the man on board swung them to show us how in themselves they could guide the vessel. There were bull’s-eye windows, like freckled patches on the hull; and under the bow, like a mouth, a tiny port swung open to expose a torpedo tube, the craft’s single weapon, with the staring eyes of the Franklin searchlights above it. We climbed over the spider-bridge and went on board. A small bull’s-eye turret came sliding up for surface cruising; a tiny door gave into it so that we might crouch through and descend the ladder. The upper slope of the hull had ingeniously opened to form a small level deck upon which we might sit with the ship awash. Even for the eighty-two-foot length and a bulge at the middle of some twenty-four-foot diameter, the interior of the Dolphin was surprisingly small. Dr. Plantet explained to me his principle of reciprocating pressures, as he called it. But I could comprehend, this day, no more than its generalities--a mere glimpse of the fundamentals of what now is so famous; and it was many months before I grasped it in detail. * * * * * There was an inner hull, so that the interior space of the vessel was considerably reduced. Within these two _ralite_ hulls, each of them reënforced with every modern device, was an intricate core of tiny passages and cells, with water circulating through them under pressure. A strange yet simple principle of hydraulics--so difficult mathematically to grasp that none before had ever imagined it. It involved many of the intricate laws of modern hydrodynamics--yet in theory simple as all great things must be. The outer hull, crowded by the immense pressures of the ocean’s depths, would give inward a trifle, to yield its pressure to the water flowing in the core. And that internal water, so swift of motion, converted the pressure we call latent into what now physicists are calling kinetic. Strange term--kinetic pressure. Strange absorption into harmless gurgling motion of this crushing ocean force which for so long had held the deeps impenetrable! I stared at Dr. Plantet. “Kinetic pressure?” Yet we have accepted as simple enough the conversion of other energies to be lost in motion. Latent energy, kinetic energy--terms simple indeed.