178 THE STORY-BOOK OF SCIENCE 



vention due to Franklin 's genius. The lightning- 

 conductor is composed of a rod of iron, long, strong, 

 and pointed, fastened to the top of the building. 

 From its base starts another rod, also of iron, which 

 runs along the roofs and walls, where it is fastened 

 with staples, and plunges into damp ground or, bet- 

 ter still, into a deep well of water. If a thunderbolt 

 falls, it strikes the lightning-conductor, which is the 

 nearest object to the cloud as well as the best suited 

 to the electric current on account of its metallic na- 

 ture. Besides, its pointed form has much to do with 

 its efficacy. The bolt that strikes the metal light- 

 ning-conductor follows it and is dissipated in the 

 depths of the earth without causing any damage. " 



