30 



trough and which should be connected to the cable as indicated later. Another 

 factor that may sometimes influence the selection of the ground-rod locations is 

 the presence of manure and the liquid from it. The ammonia in the manure will 

 attack the copper rods, and in a few years eat them off. The heat of the decaying 

 manure will hasten rusting of the iron rods. Consequently ground-rods should 

 be located where there is no manure. 



Some rodding companies in Michigan use a length of half-inch gas piping to 

 protect their ground-rods'. This pipe is first closed at one end by welding and then 

 sharpened, after which it is driven in the earth point downward until the top is 



Fig. 37.— The drill (in left hand) used in 

 making groundings. 



within a foot or so of the earth's surface. The cable is then shoved down inside 

 the gas pipe till it reaches the bottom, and the pipe then flattened at the top till 

 it presses firmly on the cable. The Patrons' Mutual of that State prefers that the 

 groundings be thus protected before they accept the risk in their rodded class, and 

 as already stated they have paid in eleven years only three lightning claims on 

 rodded buildings. The Protected Mutual, on the other hand, will not accept a 

 risk at all if they discover that the gas-pipe protection is used. They make two 

 objections against it, one that the pipe acts somewhat as a choke-coil, the other 



