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Tuesday, June 23, 2009

Opening a Book at Random, #2

What is “petrified lightning”?
Petrified lightning is a popular name for fulgurite (Latin fulgure, lightning), which consists of siliceous tubes formed vertically in loose sand by the passage of lightning. When lightning strikes sand a temperature of several thousand degrees Fahrenheit is created and the particles along the central part of the path are volatilized, driven out and fused into a tube with the interior surface glossy and smooth as glass. Such tubes extending to a depth of thirty feet or more have been found, and occasionally they are three or four inches in circumference, although generally they are smaller. As a rule the thickness of the walls is not more than one-thirtieth or one-twentieth of an inch. Sand hills unprotected by vegetation are constantly shifting[,] and not infrequently petrified lightning tubes are left projecting several feet above the surface. Sometimes the tubes are branched and a large number of them together creates the weird effect of a glass forest. Fulgurites are also occasionally produced by lightning running through a wire or cable buried in sand. Tubes resembling natural fulgurites have been produced in the laboratory by discharging electricity of a high voltage through powdered glass or sand of the proper composition.

From A Book About a Thousand Things (1946), by George Stimson


Gerry said...

The movie "Sweet Home Alabama" used fulgurites as a plot element--and in the process wildly exaggerated their size and appearance. I was captivated by the notion of lightning glass anyway. This was a fun dip into randomness!

P. J. Grath said...

Do you recommend the movie? I thought of adding something about "lightning stones," but that wouldn't have been random. Should randomness follow rules? Wouldn't that be contradictory?