35 



Our reply to this letter was in part as follows : 



" We are in receipt of yours of August 25th re the rods on your barns that were 

 burned. We note that only one barn was struck, and the second caught from the first. 

 Judging from your letter the rod ran down the gable from the peak at the north end, 

 and not from the eaves. Is this correct? We also conclude that the cable ran along the 

 peak of the barn, and that there were three uprights from this cable. Is this correct? 

 Or having a metal roof, was any cable used except at the ground-rod? 



" Did you examine the points or were they destroyed? Were any of them fused? We 

 should be glad to have sample of the rods, also one of the points, a fused one if any 

 were fused. 



" We note that the rods were in good condition, but the system of rodding is very 

 defective indeed. In the first place, there should have been at least two ground-rods. 

 In the second place, with a metal roof, the cable must leave the roof at the eaves, because 

 in a metal roof resistance and self-induction are both so small that the obstruction 

 offered by the roof, and the air-gap at the corners may be less than that of a long cable 

 from the peak, especially if air-gap is short on account of conductor-pipe, and, thirdly, one 

 of the ground-rods should have been at the south-west corner, so that the conductor-pipe 

 could have been connected to the rod. If the one ground-rod that was in had been at 

 the south-west corner, and the conductor-pipe connected, as suggested, we are satisfied 

 that your barn would have been saved. 



" We are not sure that you are right in concluding that the rods were not touched. 

 We know that whenever electricity has two nearly equal paths open to it, part goes one 

 path and part the other. Probably part of the charge went down the rod and part down 

 the conductor-pipe. It would appear that the bolt must have been a very violent one." 



" The writer has just come back from Iowa and Michigan, where he has been inves- 

 tigating the subject of protection against lightning, and without going into detail, we 

 are going to give you one or two facts learned on the trip. In the State of Michigan 

 there are two mutual companies which insure buildings all over the State. One insures 

 only rodded buildings, we shall call it the Protected Company. The other insures both 

 rodded and unrodded, we shall call it the Unprotected Company, but it keeps its rodded 

 buildings in a separate class, and this class is assessed for its own losses. Both these 

 companies are very particular in having the buildings rodded properly. Neither one of 

 them would have accepted your building in their rodded class, considering the rodding 

 defective in the respects pointed out above." 



Here is another illustration that shows the need of connecting metallic bodies 

 to the rods: A barn was rodded, the cable passed down the end to the ground. 

 Inside at a distance of about three or four feet was the end of a water-pipe. Under 

 the water-pipe stood a cow. A bolt of lightning struck the rod and the cow was 

 killed. Now what happened was probably this: Part of the charge side-flashed 

 througli the wall to the water-pipe, and from that to the cow. 



The second damage suffered by the Protected Mutual is described by the Secre- 

 tar}'- in the following words: " The other damage in 1912 was on account of a large 

 galvanized storage tank in the attic of the house, only a few feet below the rod, 

 which ran along the ridge of the building. This tank was thoroughly grounded 

 with gas-pipe, so that the lightning split and part of it followed the rafter down 

 and jumped across to the tank. TTad the tank been connected with the rod, we are 

 satisfied this damage would not have occurred." 



In nearly all cases where damage is done to rodded buildings it is found that 

 the current has jumped an air-gap. The obvious remedy is to avoid possible air- 

 gaps. If the end of that water-pipe had been connected to the cable outside the 

 barn and the other end connected to the other " ground " the cow alcove referred to 

 would doubtless have been perfectly safe. 



On page 32 attention was drawn to the great importance of having the 

 groundings properly made. The connecting of metallic parts of the structure to 

 the systems is equally important. After the correspondence with Mr. fnrrie wo 

 observed a large number of barns where the gutters, eave-troughs and cotiductor- 

 oipes were not connectcfl in the system. We are satisfied this is one reason why 

 the efficiency of rods in Ontario is only 92 to 94.5 per cent., while in Iowa it is 98.7 



