Lightning Rods

Metallic conductors intended to establish a definite line of least resistance between two bodies in opposite electrical states. The most important ancient notice of the relations between lightning and conducting metal appears to be that of Ctesias. The function of a lightning rod is twofold; first, that of conducting the charge to earth, and, second, the prevention of a disruptive discharge by silent neutralization of the cloud electrification. The latter explains why a rod should terminate in a point and likewise have good ground connection. It has been found that all exposed buildings should have lightning rods, especially if on hillsides, or near ditches which are full of running water. Houses in city blocks have no need of rods. Iron or copper conductors should be used, the latter weighing ab. 6 oz. to the foot and preferably in the form of tape. If iron is used, and it seems to be in every way as efficient as copper, it may be in rod or tape form and weighing ab. 35 oz. to the foot. The top of the rod should be plated with material which will not rust or corrode. Independent ground connections are preferable to gas or water mains. Linked conductors are of little use. Clusters of points are recommended along the ridge. There is no definitely protected area, though it has been claimed for a radius equal to the height of the points above the ground. In 1892 in U. S. lightning caused 839 fires, causing a lo on original risk of $2,921,484.