National Geographic : 1950 Jun
823 general electric Company Lightning, Quicker than the Eye, Is Analyzed by the Camera. Eleven Strokes Appear as One A central lens photographs what the eye sees, a "single" bolt to New York's Empire State Building. A second lens slowly rotating around the other records the 11 (numbered) flashes which actually sped between cloud and tower. Scientists put such seemingly unimportant facts to work protecting electrical equipment (pp. 809, 827).