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Show Lightning Strokes Are Preceded by "Feelers" Which Guide the Main Bolt Strokes of lightning are preceded by "feelers" which guide the main bolt to its objective, according to Karl B. McEachron, high voltage electrical engineer, writes a Schenectady Sche-nectady (N. Y.) United Press correspondent. cor-respondent. The lightning stroke which appears ap-pears to be a single one-way discharge dis-charge is met part way by a small flash originating from the earth, he said. This preliminary discharge attracts the main stroke and draws it to the ground. In some cases the leader stroke shoots upward to a cloud, to be immediately im-mediately followed by several successive suc-cessive Hashes over its exact path from the sky downward, McEachron McEach-ron said. The discoveries of lightning habits were made through a three-year observation ob-servation of the Empire State building build-ing in New York city, the best and most frequently struck lightning conductor that could be found. The study was conducted by the General Electric company to solve the problem of better protection to transmission lines and other electrical elec-trical apparatus. Hundreds of pictures token by a high-speed camera aimed at the 1,025-foot tower from another skyscraper sky-scraper displayed strange phenomena phenom-ena in lightning conduction. "We learned that leader strokes which precede all lightning flashes move toward the ground in a series of hesitating steps of approximately 200 feet in length," McEachron explained. ex-plained. "The streamers progress this short distance, substantially die out, and after a wait of a few mil-lionths mil-lionths of a second proceed in a second step, repeating until they reach the earth. Succeeding flashes move without hesitation at speeds of 10,000 miles per second or faster." Dr. B. F. J. Schonland in South Africa, uiing a camera similar to the one used in the New York experiments, ex-periments, also discovered that the usual lightning discharge consisted of a leader stroke, which was followed fol-lowed by a main stroke from the ground upward to cause the visible flash. |