Multiple lightning strokes — II

THE multiple stroke has been defined as a succession of discharges in substantially the same path, either between clouds or between cloud and ground. Multiple strokes are of considerable interest to the engineer, because of the possible effects of successive application of impulses to equipment with a very small cooling or resting period interposed. The author has undertaken studies of natural lightning in three different locations with three somewhat different methods, one of the objects being in each case the determination of characteristics of multiple strokes. One of these investigations is a detailed study of lightning strokes to the Empire State Building in New York, another in Pittsfield, Mass., employs photographic methods making use of an observatory erected for the especial purpose of studying lightning, and the third is an investigation of multiple strokes to transmission lines as measured by the use of the especially designed crater lamp oscillograph installed and operated in co-operation with the American Gas and Electric Company at Roanoke, Va.