2 SMITHSOXIAN MISCELLANEOUS COLLECTIONS VOL. 92 



To summarize, will say that the flash was apparently one which took place 

 between two clouds; it has the appearance of a very flexible tube of large 

 diameter, was almost instantaneous, and accompanied with a heavy downpour of 

 rain. The camera when the exposure was made was moved by hand, the camera 

 being placed on the stand described previously and was slanted upward at an 

 angle of 15° ; the speed was i revolution in 5 seconds. 



Temperature was 23° C. Barometer steady at 29.81 inches. Wind S.W. after- 

 wards changing W. and N.W., with intervals of calm. 



On the same evening [July 17, 1908] a friend of mine, R. J. Spickerman, 

 residing at 2813 Lowe Ave., about 6 miles south from my place, secured a most 

 remarkable photograph of a flash [pi. i, fig. 2], by means of a small 2^ by 3i" 

 film camera. A copy from the original photograph is enclosed, marked no. 9, 

 and also an enlargement of the same, marked no. 10. In describing how he 

 obtained the flash he said that he was sitting on the porch watching the beautiful 

 display, and having a camera, he thought that he would try his luck in photo- 

 graphing, having heard me speak of it several times. 



He held the camera on his lap, pointing it toward the southeast, where the 

 most flashes were observed. He thought that he held the camera still, at the 

 time that he secured the flash, but the photograph shows that it must have moved. 

 It shows a meandering and very complicated flash, consisting of four distinct 

 and separate rushes,^ following one another in the same path, opened up by the 

 first discharge. It is almost incomprehensible how such a complicated flash can 

 follow all those curves and bends which the photograph shows. The only rea- 

 sonable explanation to my mind would be that the path of the flash was a partial 

 vacuum with very low resistance, which the beaded or striated appearance of 

 this flash also would tend to confirm. How this partial vacuum can be ac- 

 counted for is a difficult problem to solve. It is the first lightning photograph 

 which I have had the fortune of seeing that shows the path in broken lines, or 

 striated. It is this peculiarity which makes it especially interesting. I have only 

 on one occasion observed a vertical flash which showed the path broken up in 

 alternate light and dark divisions (it is about 4 years ago). I did not succeed 

 in getting a photograph of it. 



It is possible that those beads or striae are of similar nature as those produced 

 in vacuum tubes, although they differ from them in this respect, that the striae 

 in a vacuum tube are narrow (as the name implies), whereas in the flash they 

 are wide. The word striae is really a poor term to use; beads would be more 

 appropriate, and I shall use it hereafter when speaking of them. On the original 

 photograph some of these beads are i mm long but the most of them about 

 \ mm. The dark spaces between them are on the average about i mm wide. 

 Now, saying that the angle of the lens is 36°, and the distance of the flash from 

 the camera was 10,000 feet, which is a conservative estimate, that would mean 

 that the average length of the beads would be 36.5 feet and the average distance 

 between them would be 14.6 feet. Of course these figures are only approximate; 

 they only give an idea for comparison between the striae in a vacuum tube and 

 those in the flash. These divisions seem to have been of a stationary nature, 



I think I can see six separate rushes. — C. G. A. 



