Buying the magnetometer was the easy part. Towing it was art. An operator set up a predetermined grid, then towed the instrument slowly and methodically back and forth, a process known as “mowing the lawn.” As the magnetometer detected ferrous metal objects below, the locations were recorded by the boat’s onboard computers, which would make a chart of the hits. All the while, the captain would work to keep his magnetometer at optimum altitude, about ten feet above the seafloor. In that way, surveys often turned into an ongoing waltz with the sea. The finest captains were the ones who could
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