124 PHOTOGRAPHING LIGHTNING WITH MOVING CAMERA. 



LlfjJitnhxj f<(sh {fig. 5) — Continued. 



In the summer of 1005 a new departure was undertaken hy the 

 writer at the suggestion of the Secretary of the Smithsonian Institu- 

 tion, the. object being to obtain spectrum photographs of lightning. 



Spectroscopic examinations of lightning have beeii made by many, 

 but most of these observations have been visual, which at their best 

 can only be rough' approximations of the number of lines and their 

 I'elative positions. As far as the writer knows, only one institution 

 in the country — the Harvard College Observatory — had undertaken 

 any work in photographing the spectrum of lightning. 



A crude apparatus was constructed, consisting of a camera with a 

 85-millimeter prism fitted in front of the lens, no slit being used, as 

 a lightning flash is a relatively narrow streak of light yielding a prac- 

 tically parallel beam. By. means of this arrangement a few photo- 

 graphs have been obtained, two of which are reproduced in figures (> 

 and 7. A spectrum photograph of a spark from a static machine, for 

 comparison, is shown in figure 8. 



The spectrum shown in figure 6 is from a vertical flash, the picture 

 of which was obtained June 18, 1905. It was about 1^ miles distant 

 and was taken at the end of a storm of local character. The spec- 

 trum of this flash resembles that from the static machine in most of 

 its details, 



