LIGHTNING AND THUNDER. 221 



the lower terminal, is of the utmost importance ; and 

 in a majority of cases of injury to buildings from badly 

 constructed conductors, such injury is traceable to 

 imperfect earth terminals. 



The terminal should connect with damp earth, at a 

 sufficient depth below the surface, to insure permanent 

 dampness, and hence permanent conductivity. And, 

 to render this connection more complete, it should 

 bifurcate below the surface ; and be connected by sol- 

 dering, with a mass of metal, buried in the earth. The 

 hole, in which this mass is buried, should be filled to the 

 surrace with cinders or coke, to facilitate the percolation 

 of water; and any available drainage of pure water, 

 from rain water pipes or otherwise, connected with it. 



The metal mass may be of copper or galvanized iron, 

 having about eighteen square feet of surface. And 

 where permanently damp earth is not available, it 

 should consist of three or four hundred pounds of iron. 



Where the use of large iron water or gas mains is 

 available, a connection by a copper strip, can be made 

 with them ; no risk being incurred by such connection, 

 as in the case of internal supply pipes. 



INSPECTION. Periodical inspection, and careful elec- 

 tric testing, are requisite to maintain the system in 

 efficient order ; as points may corrode or become fused, 

 joints become electrically imperfect, connections be- 

 come severed above or below ground, or other im- 

 perfections occur, from alterations in the building, and 

 the carelessness or ignorance of occupants or workmen. 



The author has, on his house, a copper tape conductor, 

 constructed in accordance with these principles, and 

 erected twenty-three years ago ; and neither the house, 



