LIGHTNING RODS 437 



communities and localities where there are few high trees 

 and improvements projecting into the air or extending 

 to any great depth into the earth. As good connections 

 between the moist earth and the cloud are not available, the 

 charge accumulates in the cloud until a discharge is neces- 

 sary, when it passes through the nearest and least resistant 

 object. The greater the resistance that is offered by the 

 object through which the current is passing, the more 

 damage will be done by the current. Where there are suit- 

 able conductors and enough of them, the electric current is 

 equalized by a continuous flow from the cloud to the earth, 

 and dangerous accumulations are thus prevented. It has 

 been observed that lightning seldom strikes in cities and 

 that metal objects such as locomotives and steel ships are 

 apparently immune. Smoke stacks, high buildings with 

 steel frames, wiring systems, etc., of the city, are projecting 

 into the air as well as deep into the ground and offer an 

 easy route for the current. As a result, the equilibrium 

 between the earth and the cloud is maintained and damaging 

 lightning strokes do not occur. 



When an animal or a building is in the path of the light- 

 ning, death or fire is likely to be the result. Since water 

 offers less resistance than dry earth, the current will tend to 

 pass through an object that leads into moist earth, and as 

 warm air offers less resistance than cold' air, there is a tend- 

 ency for the current to follow the warm air. This may 

 account for the fact that animals are frequently killed in 

 an open pasture, because during a storm they have a tend- 

 ency to crowd close together and their bodies warm the 

 air above them. Animals are also killed when standing 

 close to a wire fence. The current is carried on the fence 

 and passes through the body of the animal in reaching the 

 ground. The dangers of lightning stroke are materially 

 reduced when the rain begins to fall, because each drop 

 comes to earth with a charge which assists the neutralizing 

 of the stress between the cloud and the earth. 



