Lightning Rods as a Protection to Buildings.
Lightning rods properly installed are almost an absolute protection and out of every $1,000 worth of damage done to unrodded buildings by lightning, $990 would be saved if the buildings were properly rodded—a very strong statement—but it has taken thirteen years of investigation to compile data that enables us to make that statement. From reports of eighteen insurance companies it is found that in every two hundred farm buildings insured, forty-two are rodded, but out of every two hundred struck by lightning only three arc rodded—we should expect forty-two if the rods were no good. Or, stating it in another way, in every seven thousand unrodded buildings insured by these companies, thirty-seven were struck and several burned, but out of every seven thousand rodded ones, only two were struck and only slightly damaged, while we should expect thirty-seven if the rods were no good. Hence, an unrodded building is eighteen and one-half times as likely to be struck as a rodded one is. These results cover all kinds of rods and doubtless include some improper work. To prevent damage in thirty-five out of a possible thirtyseven means an efficiency of 94½ per cent., so I am fully justified in concluding that experience establishes the claim of science, that lightning rods as installed, proper and improper, do actually prevent lightning from occurring in ninety-five cases out of one hundrred where strokes would occur if the buildings were not rodded. But, despite our logic, we do not expect to convince all our hearers by reports covering one year. For those who want reports for a period of years, we have them. Our attention has been drawn to the States of Iowa and Michigan, where advanced work was done in rodding. In September last, I was able to visit these states and examine conditions for myself. In Iowa, I found some valuable compilations had already been made for the eight years, 1905-1912 included. F”ifty-fivc insurance companies have reported the percentage of rodded buildings covered by their risks and also the claims paid on rodded and unrodded buildings. These companies report that 50 per cent, of all their risks are rodded. The total lightning claims paid by all these companies for the whole eight years on rodded buildings was only $4,464.30, which is an average of $10.15 per company per year. On unrodded buildings lightning claims of $341,065.32, which is an average of $775.15 per company per year and the number of unrodded buildings was the same as of rodded ones. Comparing $775.15 with $10.15 we see that the rods save $75 out of an expected loss of $76 if the buildings were not rodded, and it is possible that some improper rodding is included as the work was not inspected. This case is not as yet complete. Iowa reports cover some defective rodding. True efficiency of lightning rods can only be determined when we consider a large number of properly rodded buildings. The Farmers Mutual Lightning Protection Insurance Company, of Michigan, insured only rodded buildings and only after the company’s inspectors have carefully examined the rodding. For the four years, 1909-1912 inclusive, in a business which totalled $56,000,000, this company paid $3,200 for damage done to buildings by lightning in three claims, all traceable to minor defects in rodding. The Patron’s Mutual Insurance Company, which does business all over Michigan, insures both rodded and unrodded buildings. In the same four years on a total risk of $60,000,000, this company paid lightning damage to the extent of $33,000, which is 1,008 times as much as the protected company paid. The secretary of the Patron’s Company told me that in eleven years they had only three small claims for lightning damage on rodded buildings. They report 20 per cent, of their risks rodded. Deducting these rodded risks amounting to $32,269 damage occurred in unrodded risks amounting to $47,753,818. At this rate the loss on $55,000,000 of unrodded risks, the same as the protected company, would be $37,282, which is 1,168 times as great as the loss on the same amount of properly rodded risks. Thus we see that when the damage to properly rodded buildings amounts to $1, the damage to unrodded buildings amounts to $1,168, or in other words, the rods saved $1,167 out of a possible $1,168, indicating an efficiency of 99.91 per cent., or $999 out of $1,000.