194 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1925 



ARKA PROTECTED BY A ROD 



The general character of the division of hits between a rod and 

 the surrounding ground is shown in Figure 35. In this specific 



Storm Center 



a 14 IZ 10 8 6 4 Z'JO/l^^ t 8 10 H M 

 Protected Area ^ 



h H 12 10 8 6 4 Z Z ^ 6 8 IQ }Z 14 



c /4 12 10 8 



Fig. 35. — Protected area and distribution of hits between rod 

 and gmund for different positions of storm center 



example, taken for illustration, the rod is located on a conducting 

 plane and is 1.85 per cent of the cloud height. In (a"). Figure 35, 



^ 10 

 9 

 8 



>3 



o 



I / 



'^ 



02 0.4 OB O.S 1.0 12 14 1.6 15 20 22 

 Height of Rod in percent cf Cloud Height 



Fig. 36 



the storm center is located directly above the rod. Under this 

 condition 84 per cent of the strokes hit the rod. while 16 per cent 

 hit the ground approximately as shown in the shaded portion. 



