Dr. A. Schuster on Spectra of Lightning . 



319 



spot of the sky was illuminated during some flashes with a 

 strong blue light, looking like a fluorescent light. I pointed 

 the spectroscope to that spot, and observed a single broad band 

 in the green. I moved the pointer on it as well as I could ; 

 but not being able to get another flash to verify the measure- 

 ment, I had to take the reading. The position of this band, 

 which I call S, is very doubtful. 



August 18th, Salt-Lake City. — I only obtained one mea- 

 surement of the band y. The kind of lightning observed differed 

 considerably from that of the preceding nights. The lightning 

 was nearly all forked lightning; and the bright nitrogen- 

 line came out very strongly. The bands were but seldom seen. 

 In one flash I saw a series of lines in the green which I had 

 never seen before. My impression is that they were at about 

 equal distances from each other, decreasing in strength towards 

 the red; so that the whole made an impression similar to that 

 of a fluted band, such as those seen in the spectrum of alu- 

 minium oxide, but shading off towards the red. 



In addition to the line and band spectra, I have on many 

 occasions seen a continuous spectrum only. 



The following Table contains all the measurements I have 

 taken. I have added in the last column numbers contained 

 in Dr. Vogel's list of lines. It will be seen that these coincide 

 with two of the bands I have seen. 



Band. 



Date. 



\ 



Mean. 



Vogel. 



a. 



July 25 



5592 



5592 





0. 



July 25 

 July 25 

 Aug. 3 



5348 

 5329 

 5325 



5334 



5341 



r- 



July 25 

 July 25 

 Aug. 18 



5175 

 5193 

 5177 



5182 



5184 



s. 



Aug. 3 



5260 



5260 





In trying to identify these bands with known spectra we 

 meet with an unexpected difficulty. Two of them unfortu- 

 nately admit of two different interpretations. At first sight 

 I was struck by the close agreement of « and <y with two bands 

 of carbonic oxide. These bands fade away towards the blue; 

 and their sharp edges have a wave-length ' of 5607 and 5197. 

 Observing with the same spectroscope, and widening the slit 

 as I did in observing the lightning, I can produce the same 

 impression of an unshaded band; and taking a measurement of 



202 



