National Geographic : 1945 Jan
The National Geographic Magazine iMaurice Ewing How the Moon Makes the Tides Ebb and Flow Is Recorded at Seaside Stations All over the world a close check is kept on how the tides are running, as an aid to ships entering and leaving harbors. This tide gauge at St. George, Bermuda, has a float inside the vertical pipe, protected from the pounding of the waves. Tidal rise and fall are recorded in galvanized-iron shelter above. a handful of earth or rock from equally scat tered locations! Yet we've had to base our knowledge of the deeper parts of the ocean bottom on far more meager information. Greatest Known Ocean Depths Greatest known depth in the ocean is 35,400 feet (6.7 miles), in the Mindanao Deep off the Philippines. Mount Everest, world's highest mountain, would be more than a mile under water if submerged there. Other great deeps are: Bartlett Deep, south of Cuba, 22,788 feet (4.3 miles); Wharton Deep, just south of Java, 22,968 feet (4.4 miles); Richards Deep, off Chile, 25,050 feet (4.7 miles); Milwaukee Depth, north of Hispaniola, 30,246 feet (5.7 miles); Nero Deep, southeast of Guam, 31,614 feet (6 miles); and Ramapo Deep, off Japan, 34,626 feet (6.6 miles). Conditions down on the hidden ocean bot tom are hard to imagine. There live creatures which never in all their lives are as warm as a cake of ice. Because salt water freezes at a lower temperature than fresh, water in the ocean depths stays liquid even where its tem perature is below 320 F., the freezing point of fresh water. Sea-bottom mud dredged up in the Tropics by the British scientific ship Chal lenger was so cold that the officers chilled their champagne in it. Everything that sinks in the sea sinks all the way to the bottom, contrary to the old be lief that ships, dead bodies, and other things "find their level" at various depths and remain suspended there. Despite the great pressures, up to six or seven tons to the square inch, nearly 1,000 times that on the ocean surface, any solid object, or anything into which water can penetrate, such as the body of an animal, is not greatly changed by sinking to the bot tom. But closed glass thermometer tubes, even when protected by metal cases, have been crushed to powder.