On Lightning- Rods. 335 



Lightning-Rods for Churches. 



For a tower, the stem of the rod should rise 15 or 25 feet, 

 according to the area : the domes and steeples of churches 

 being usually much higher than surrounding objects, do not 

 require so high a conductor as buildings with extensive flat 

 roofs. For the former, therefore, their stems, rising six feet 

 above the cross, or weathercock, will be sufficient ; and being 

 light, may be easily fixed to them, without altering their ap- 

 pearance, or interfering with the motions of the vane. 



Lightning-Rods for Powder-Magazines. 



These require to be constructed with the greatest care. 

 They should not be placed on the buildings, but on poles, at 

 six or ten feet distance. The stems should be about seven 

 feet long, and the poles of such a height- that the stem may- 

 rise fifteen or twenty feet above the building. It is also ad- 

 viseable to have several lightning-rods about each magazine. 

 If the magazine be in a tower, or other very lofty buildisig, it 

 may be sufficient to defend it by a double copper conductor, 

 without any stem. This is done on the European continent. 

 As the influence of this conductor will not extend beyond the 

 building, it cannot attract the lightning from a distance, and 

 will yet protect the magazine should it be struck. 



Lightning-Rods for Ships, 



The stem of a lightning-rod for a ship consists merely of a 

 copper point, screwed into a round iron rod, entering the ex- 

 tremity of the top-gallant mast. An iron bar, connected with 

 the foot of the round rod, descends down the pole, and is 

 terminated by a crook, or ring, to which the conductor of the 

 lightning-rod is attached, which in this case is formed of a 

 metallic rope, connected at its lower extremity with a bar or 

 plate of metal, and which latter is connected to the copper 

 sheathing on the bottom of the vessel. Small vessels require 



