National Geographic : 1954 Jul
69 card withdrew to build his own bathyscaphe, the Trieste, in Italy, using part of the French plans. We were happy that the world's "bathy fleet" had been thus augmented. As for me, I looked forward to the coming dive as the greatest experience of my undersea investigations, the more so because of the work I had engaged in for months with Dr. Harold E. Edgerton, of the Massachusetts Institute of Technology,* who invented the strobo scopic flash for high-speed photography. As part of a National Geographic Society research project, we had been using his auto matic electronic flash cameras in the depths from aboard our oceanographic vessel, Calypso. Our target was the mysterious "deep scattering layer," often known by its initials -the DSL. Echoes Bounce Off "Phantom Layer" The problem of the DSL is a recent one in oceanography, appearing with the advent of the echo-sounding device in the 1930's. In all seas, echo sounders had recorded a puzzling layer or layers, rising by night, sinking by day, between the surface and the actual sea floor, often at 250 fathoms. Even in the mid-Atlantic, expeditions sponsored by the National Geographic Society, Woods Hole Oceanographic Institution, and Columbia Uni versity had found this same "phantom layer."t What was the DSL? Some scientists at first thought it a stratum of water markedly dif ferent in temperature, salinity, or other physi cal factors. Others decided it was a crowded * See "Burr Prizes Awarded to Dr. Edgerton and Dr. Van Biesbroeck," NATIONAL GEOGRAPHIC MAGA ZINE, May, 1953. t See, in the NATIONAL GEOGRAPHIC MAGAZINE: "New Discoveries on the Mid-Atlantic Ridge," No vember, 1949; and "Exploring the Mid-Atlantic Ridge," September, 1948, both by Maurice Ewing.