Progressive Lightning

Abstract

I HAVE to thank Dr. Perrine for his observations on my article on “Progressive Lightning.” They are interesting as indicating some difference in the appearance of lightning in the Argentine, where the strokes are exceptionally strong, and that of lightning in Great Britain. Here without any question the appearance of the multiple flash is found when the distance is as little as a kilometre, and I certainly believe much less. In Cordoba Dr. Perrine only observes this when the flashes are so distant that thunder is barely beard. Such a distance here is from sixteen to twenty kilometres. I suppose here, with a flash near enough, even if it were multiple, the eye would be so dazzled by the primitive flash as not to be able to see those that follow, but it is difficult to account in this way for the great distance implied by the faint audibility of the thunder. I have seen a large number of photographs taken with an ordinary camera held in the hand, and not intentionally moved as Dr. Hoffert's was, but nevertheless not really fixed, which show the multiple flash, and the size of the flashes on the plates indicates that they must have been fairly near. At any distance such as sixteen kilometres the flash would occupy but a small portion of the plate.