Tuesday, August 28, 1900
16 N, 49.3 W

The vortex gained definition. Rivers of air flowed toward its center. The earth's rotation drove them to the right, but each right-veering gust imparted to the vortex a left-hand spin, just as a glancing blow on the right side of a cue ball will cause it to spin left. The arriving winds lowered pressure. As the pressure fell, air moving toward the storm gained velocity. The stronger winds drew more water vapor from the sea, which fed the clouds around the center of the vortex -- releasing more heat and driving the pressure still lower.

On Tuesday, August 28, the storm overtook a ship located about three hundred nautical miles southeast of Monday's first sighting. The ship's log noted winds from the south-southwest, the bottom right rim on a Piddington horn card. The wind was stronger, Force 6, twenty-five to thirty-one miles an hour.

Guy wires whistled.

Excerpted from ISAAC'S STORM. Copyright © 1999 by Erik Larson.

Copyright © 1999, Random House, Inc.