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Reading the Depths

Working on the deck of the R/V Atlantis, William Shultz disassembles a bathythermograph, or BT—a torpedo-shaped device containing sensors that detect changes in water temperature and pressure. Developed in the 1930s by Athelstan Frederick Spilhaus, thousands of BTs were launched and retrieved from oceanographic research vessels and navy ships from 1940 to the mid-1960s. The device also played a major role in defense against German submarines during World War II.(Photo by Jan Hahn, Woods Hole Oceanographic Institution)