Lightning Lore

To the top of Pittsburgh's grimy Gothic Cathedral of Learning went Dr. Gilbert D. McCann last week, there to bait his traps for thunderbolts and thus officially open the 1943 lightning season. Other claptraps (more than 200) were set out along power lines, on forest watchtowers, atop radio masts and the tall stacks of copper smelters--wherever lightning is likely to strike twice.

If the new season is up to average, lightning will kill some 400 people by October,* burn up about twelve million dollars worth of farm buildings, cause half the oil-tank fires, set forests ablaze across the country, scare millions of picnickers and bathers, and add new legends to already existent vulgar errors.

Young (31) Dr. McCann has been a Westinghouse lightning hunter for five years. His full-time job is the study of lightning's quirks for the protection of life and property, particularly the vulnerable equipment of power companies, and--these days--explosives plants. Because he cannot always whistle up a black thunderhead to observe, between bolts he works with laboratory lightning.

His traps record both intensity and duration of the flash. Electric-eye cameras reveal the number of separate pulses within a single stroke. Another device (the fulchronograph) clocks the quickest stroke and measures the amount of current. Its heart is an ever-turning aluminum wheel, with hundreds of small strips of magnet steel projecting from its rim. Lightning, when it strikes, creates an electrical field in coils which magnetize the strips. When the fins are removed in the laboratory their magnetism is measured, gives the strength of the stroke charted.

Biggest bolt ever recorded: a flaring snapper which hit the 585-ft. smelter stack of the Anaconda Copper Mining Co. at Butte, Mont., in the summer of 1941. Its current totaled more than 160,000 amperes; its estimated pressure exceeded 15,000,000 volts. (Ordinary home circuit: 110 volts.)

Sample lightning findings, from Ben Franklin to Dr. McCann:

> Electrical charges accumulate in clouds, positive at the top, negative on the bottom. A spark bursts through the air to another cloud or to the earth--lightning. First comes a faint leader stroke, then a huge discharge builds upward from the earth. The slender core (about the thickness of a finger) explodes into a column of fire much greater in diameter. As this heated air cools and contracts, other air rushes in to fill the space. This sudden disturbance makes the thunderclap.

> Destruction comes from the speed of the discharge, not the total amount of electricity: the quantity of electricity in an average thunderbolt would be worth only a few cents if tamed and metered.

> New Mexico, Arizona, Georgia and Mississippi are the most lightning-liked states, with an annual fatality rate of ten in a million population. Pacific Coast states and the Middle Atlantic seaboard states are the safest: (less than two per million in Pennsylvania, New York, New Jersey and southern New England).

> Avoiding drafts, closing doors and windows will not keep out lightning. It is most likely to hit the chimney. Safest place in the house: the middle of a downstairs room.

> Telephones are not unsafe in a thunderstorm. The crackling and tinkling are caused by induction charges.

> Thick woods are safe enough, but isolated trees are bolt-catchers. Since they are poor conductors, lightning may take the easier way through humans standing near.

*About the same number killed in streetcar accidents; half the number killed by the heat.

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