Harmless Discharge 



325 



especially if there are tin or iron water pipes 

 running to the ground. Even steam and gas 

 pipes are good if connected with the roof. 

 Tin and copper roofs are not so common in 

 the country as in the city, and this is one of 

 the many reasons why city houses are less 

 frequently struck by lightning than country 

 ones. Copper roofs are not used now as they 

 once were on account of the great expense; 

 but from the electrical standpoint they are an 

 excellent protection to a house in a thunder 

 storm. The writer has 

 noticed in a room in a 

 city house, in which 

 steam heat is used, that 

 the lightning will come 

 in and down on the 

 steam pipes without 

 doing any harm. If 

 one will go into a tele- 

 graph station during a 

 storm he wall frequently 

 notice the discharges of 

 1 ightning which take 

 place through devices 

 provided for the pur- 

 pose, and this without the least fire risk. 

 This is an illustration of the fact that, if 

 properly provided for, the dangerous element 



Fig. 133. Tree-form discharge. 



