Bathyscaphe, submarine vessel designed to operate at great depths. The first such vessel, invented in 1947 by the Swiss physicist Auguste Piccard, explored the ocean bottom at a depth, in 1954, as great as 4000 m (13,125 ft) and operated under water pressure of 0.42 metric ton/sq cm. The bathyscaphe Trieste, built in 1953, set a world record on January 23, 1960, when it descended 10,915 m (about 35,810 ft) to the bottom of the Mariana Trench, deepest known point in the oceans, 338 km (about 210 mi) southwest of Guam. It withstood pressure of 1.17 metric tons/sq cm at that depth. The craft, which carried gasoline for buoyancy and iron pellets for ballast, descended when water was pumped into air tanks at either end and ascended when water was pumped out and the pellets released. The dive, manned by the Swiss scientist Jacques Piccard, the son of Auguste Piccard, and Lieutenant Donald Walsh of the U.S. Navy, yielded important geophysical information. The Trieste was also used in the search for the hull of the nuclear submarine USS Thresher, which had plunged 2560 m (8400 ft) to the ocean floor 354 km (220 mi) east of Boston in April 1963. After an exhaustive search, the Trieste recovered only scraps of metal and equipment, leading the Navy to believe that extreme pressure caused the submarine to implode before it hit the ocean bottom. This theory was confirmed during covert operations to survey the wreckage in the 1980s. See Deep-Sea Exploration; Geophysics.
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