POPULAR SCIENCE MONTHLY. 



support of the vortex theory. Fig. 4 shows the marks left by a 

 stroke of lightning on the wall of a house at Mort, illustrating its 



course from the iron 

 water pipe to the iron 

 hinges of the window, 

 and from thence to the 

 iron sewer grating. 

 For comparison he 

 sends two other photo- 

 graphs (Figs. 5 and 6). 

 These are obtained by 

 the discharge of an im- 

 mense Ruhmkorff in- 

 duction coil containing one hundred thousand metres of insulated 

 copper wire. Two small triangles of tin foil are glued opposite to 

 one another on a photographic plate, and when dry the whole is 



Fig. 6. Discharge of a Ruhmkobff Induction Coil. 



Fig. 7. Artificial Solar Eclipse. 



covered with a light brownish coating of lampblack. After the 

 discharge a white track is found, as shown in the photographs. 

 Both these pictures show evidence of the vortex motion of the 



