Lightning Page 141

cellar into the back shed, then jumped to a sink, scaring the tar out of her son who was repairing his bicycle in the shed.

Some of the phenomena manifested by lightning are so weird that it becomes hard to separate fact from fiction. For instance, ball lightning was long thought to be an old wives' tale. Too many credible observations by competent personnel have been reported, however, to pass it off as a myth. Present theories consider the phenomenon to consist of a small, heavily charged mass of ionized air that becomes separated from the path of a stroke and then drifts along with natural air currents until it either dissipates or finds a ground path where it discharges, sometimes with explosive violence. Sheet lightning is thought by some to be merely reflections of lightning discharges in a faraway cloud. Others think it is the instantaneous discharge of a large area of atmosphere, spreading the energy that would otherwise be discharged in a stroke over a wide area a sort of high-speed Aurora Borealis.

People have gone to great lengths over the years to protect themselves from lightning, ranging from charms and prayers to more scientifically sound methods. When Mr. Franklin invented the lightning rod, all sorts of applications were tried. An early drawing depicts an umbrella with a lightning rod on top and a conductor trailing off along the ground. Good thinking, but a very dangerous device. Lightning rods today are confined to the tops of buildings.

Modern-day lightning rods are generally pointed, not so much to make them more likely to be hit as to prevent the buildup of charges that would lead to a stroke. It is generally known among those who work with high potentials that a point encourages corona discharge. Working on that principle, the point on a lightning rod constantly bleeds off accumulating charges thus preventing their building up to a dangerous level.

In the communications field, lightning protection varies depending not only on the nature of service but on the geographical location as well. This is because the frequency and severity of thunderstorms varies throughout the continent. Equipment that is protected sufficiently on the west coast would go up like a Roman candle in central Kansas or on the Florida peninsula. In the latter two areas, electricians do as much business repairing lightning damage as they do putting in new installations. The Great Lakes region has 50% more thunderstorm activity than the New England coast. By contrast, southern Alaska has perhaps only