Insulator's 



331 



rod, its form is a matter of considerable im- 

 portance. The cable forms have been used 

 extensively and successfully, but the ribbon or 

 flat form is better on account of the smaller cost, 

 and because there is a greater area exposed for 

 the dissipation of the heat generated by the 

 lightning in passing from the points to the 

 ground. A rectangular section of three-quarters 

 by one -eighth of an inch is recommended. 



In supporting the conductor from the wall or 

 roof, it should be separated or "in- ; 

 sulated" from these surfaces. There 

 is a slight chance that the lightning 

 might leave the conductor if the build- 

 ing were wet. A more important ^ 

 reason for the use of the insulator J^^ 

 is that the heat which is generated 

 on the surface of the rod when a 

 heavy discharge occurs will not be 

 able, if supported away from the 

 wall, to heat up any inflammable ma- 

 terial near it. Fig. 135 shows a 

 method of support in which one of 

 the standard insulators used in run- 

 ning electric light and other wires is 

 employed. These insulators, which «uppoi-ti»g -^ '"J- 

 are made of porcelain and iron, can be 

 screwed into the wood or into a plug driven 

 into the joints between the stones very readily. 



Fig. irff) 



