Lightning to the Empire State Building

Abstract
Lightning to the Empire State Building in New York City has been under investigation since 1935. Boys camera photographs of 62 strokes have been taken and 99 oscillograms. Twenty of these were taken simultaneously with photographs of the same stroke. Upward step leaders were discovered and continuing strokes were shown to be in the nature of a direct current arc. A brief résumé of the more important results up to the end of the 1937 season is given. The paper is chiefly concerned with the oscillographic results of the 1938 and 1940 seasons. The low speed oscillograph in the Empire State Building recorded 17 of the 20 strokes to the building while the high speed oscillograph recorded 41 current peaks in 13 strokes. 1. Of 49 strokes recorded oscillographically during the years 1937-40, no stroke has been entirely positive although 41, or 84 per cent, were entirely negative. The first recorded current peak in stroke 13 was positive and had a crest current of 58,000 amperes. 2. Fifty per cent of the 49 strokes had charge of 25 coulombs or more, the maximum charge measured being 164 coulombs. These values are for the total stroke and not for current peaks. 3. Ninety-one per cent of all strokes recorded to the Empire State Building are classified as continuing, i.e. had a low current component. 4.

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