Dr. Hare on Lightning Rods. 323 



have been sufficiently near to endanger the premises. Noth- 

 ing in my opinion can be more erroneous than this notion. 

 The truth is, that the earth and the thunder clouds being in op- 

 posite electrical states, the electric fluid tends to pass from 

 one to the other, in order to restore the equilibrium. The 

 atmosphere being a non-conductor, through which a dis- 

 charge cannot be accomplished without a forcible displace- 

 ment of air, any solid body rising above the earth's surface, 

 which may be more capable than the air, of transmitting elec- 

 tricity, is made the medium of communication. Metals being 

 pre-eminently capable of acting as conductors, the transmi- 

 sion of electricity is made through them, with proportionably 

 greater facility. Yet they do not attract it more than other 

 substances, similarly electrified. A glass, or wooden ball, is 

 as readily attracted, by the excited conductor of an electrial 

 machine, as a ball of metal ; and as much more, than a me- 

 tallic point, as the superficies of the ball, may be greater than 

 that of the point. 



Nothing, to me, appears more unfounded than an idea, 

 lately suggested, that the attraction between a ship, and a 

 thunder cloud, can be increased, by the presence of a point- 

 ed metallic rod surmounting the main-mast. 



If houses, or vessels, have been struck with lightning, 

 while provided with conductors, it is, in my opinion, owing 

 to the conductors being improperly constructed ; or having 

 no adequate connexion with the earth. The power of any 

 body to receive an electric discharge, is dependant on the 

 conducting power of the medium in which it terminates, no 

 less than upon its own. A metallic rod, held by a glass han- 

 dle, or entering a mass of pounded glass, or dry sand, would 

 not be more efficacious, as a conductor, than a glass rod 

 similarly situated. If terminated by an imperfect conductor, 

 as for instance by earth or water, its power is reduced in pro- 

 portion to the imperfection of the medium thus bounding it. 

 This influence of the media, in which conductors terminate, 

 has not been sufficiently insisted upon in treatises on electri- 

 city. I should not consider a metallic rod, terminating, with- 

 out any enlargement of surface, in the water or the earth, as 

 an adequate protection against lightning ; but were such con- 

 ductors to terminate in metallic sheets, buried in the earth or 

 immersed in the sea, or by a connexion duly made with the 

 iron pipes, with which our city is watered, or the copper with 

 which ships are generally sheathed, I should have the most 

 perfect confidence in their competency. 



