Bathyscaph

Bathyscaph, submersible deep-sea research vessel, invented by Auguste Piccard in the late 1940s, comprising a small, spherical, pressurized passenger cabin suspended beneath a cigar-shaped flotation hull. Before dives most of the flotation tanks in the hull are filled with gasoline, the rest with air. For dives, the air is vented and seawater takes its place; seawater is allowed to enter the gasoline-filled tanks from the bottom, compressing the gasoline and increasing the density of the vessel. To begin descent, iron ballast is jettisoned. As the vessel rises, the gasoline expands, expelling water from the flotation tanks, thus lightening the vessel further and accelerating the ascent. Battery-powered motors provide the vessel with a degree of submarine mobility.