LIGHTNING AND THUNDER. 217 



the world, a code of rules for the construction and 

 erection of lightning rods, or conductors, was adopted 

 December 14, 1881; which is substantially as follows: 



RULES FOR THE CONSTRUCTION^ AND ERECTION OF 

 LIGHTNING CONDUCTORS. 



POINTS AND UPPER TERMINALS. As the point of 

 the upper terminal, from its peculiarly exposed position, 

 is liable to be fused by a heavy charge, it should not 

 be sharper than a cone whose height is equal to the 

 radius of its base. But, to secure the peculiar advan- 

 tages derived from sharp points, three or four such 

 points made of copper, each about six inches long, 

 should be attached to a copper ring ; which should be 

 screwed or soldered to the terminal, about twelve inches 

 below its highest point. And all points should be so 

 platinized, gilded, or nickel-plated, as to resist oxidation. 



The number of terminals required, their height above 

 the building, and the number of conductors connected 

 with them, depends on the size and style of the build- 

 ing, and the conductivity of the material of which it is 

 constructed. 



All elevated parts, such as turrets and spires, should 

 be protected by terminals : and especially chimneys, 

 whose liability to receive a discharge is greatly increased 

 by the heated air and soot. 



Factory chimneys should have a copper band round the 

 top; with stout, sharp, copper points, each about twelve 

 inches long, projecting from it at intervals of two or three 

 feet, and specially guarded against oxidation. And the 

 conductor, attached to this band, should be attached to 

 all bands and metallic masses in or near the chimney. 



SPACE PROTECTED. No definite rule can be given 



