The invention of the barometer by Evangelista Torricelli in 1643 is arguably the most important moment in the history of the atmospheric sciences. Because hurricanes are accompanied by dramatic drops in air pressure, a device like the barometer that measures air pressure is an indispensable tool for meteorologists and sea captains alike. For Larson, barometric readings serve as helpful literary tool for narrating the story of the Galveston hurricane and communicating its severity to readers. In fact, some of the book's most effective passages tell the storm's story through sheer data. When checking in on Blagden who is hunkered down in the Levy Building, Larson writes, "At [five o'clock Galveston time], the barometer read 29.05 inches. Nineteen minutes later, 28.95. At 6:40 p.m., 28.73 inches. Eight minutes later, 28.70. An hour later, the barometer read 28.53 inches, and continued falling. It bottomed at 28.48. […] At the time, it was the lowest reading ever recorded by a station of the U.S. Weather Bureau" (194).

The reader, knowing about barometric pressure from earlier sections, can keenly understand why these are such dramatic figures. It reminds one of an earlier section in the book when Halsey, the grizzled and hardened sea captain who believed he had seen it all, is terrified to see that his ship's barometer "had fallen to the remarkable figure of 28.