To its public list of gadgets for locating castaways at sea (Very pistols, dye markers, a hand-cranked automatic radio, etc.) the U.S. Navy added another that has vastly more range and accuracy than al] the rest. The latest, perfected too late for use in World War II but due for plenty of use, nevertheless, is a long-range underwater sound system called Sofar (Sound Fixing and Ranging).
Sofar, a by-product of wartime submarine detection research, is as curious as it is practical. A five-pound bomb, tossed into the water by the survivor, explodes under hydrostatic pressure 3,000 to 4,000 feet under sea. Sound...