200 STATE BOARD OP AGRICULTURE. 



SYSTEM OF LIGHTNING PROTECTION USED ON COLLEGE 



BARNS. 



BY L. J. SMITH_, INSTRUCTOR IN FARM MECHANICS. 



The planning of protection for the college barns was carried on 

 with special attention to the needs of the average farmer along this line. 

 The aim was for a cheap yet durable construction, simple enough for 

 the farmer to make if he has the use of a forge, drill, and set of dies 

 and taps. If these tools are not accessible, that part of the work in 

 which they would be used can be done by any blacksmith. 



Though the individual may buy his lightning rods from any of the 

 several reliable firms who have such goods on the market, there is no rea- 

 son why he should not install the rods himself, and the following pages 

 may be of interest from that standpoint. 



DISCUSSION OF MATERIALS USED. 

 CABLE. 



A y-2\ seven strand, double galvanized iron cable was used as 

 the conductor. The only practical advantage of copper over the iron 

 cable is in durability, the difference in conductivity being immaterial 

 in lightning rod construction when the distance from the points to 

 the "grounds" is relatively short. Indeed, it is maintained by some 

 authorities that the higher resistance of the iron cable is of distinct 

 advantage in that it prevents the charge from grounding so violently 

 When we think of the durability of common single galvanized fence 

 Avire, it is evident that a cable containing seven strands of larger wire 

 double galvanized, will be serviceable for a long period of j^ears. The 

 difl'erence in cost of iron and copper cable will more than offset their 

 difference in durability. The above considerations led to the selection 

 of iron cable for the conductor. 



A %'' seven strand double galvanized iron cable is undoubtedly of 

 sufficient size for the average barn or house. The I/2" cable is quite 

 stiff and heavy to handle and will take more time to put 6n the 

 building. The %'' cable costs about three cents a foot, the %" two 

 cents. However, the essential thing is to have the cable heavily galvan- 

 ized. Any hardware firm can get double galvanized cable sent them 

 in a few days. 



STAPLES. 



The cable was fastened to the building without insulation by the 

 means of 3" staples ]>laced from 24 to 30 inches apart. Two and one- 

 half inch staples will do very well if they can be readily secured. 

 Holes were drilled for the staples by the use of a gimlet bit and brace, 

 as the staples split the shingles and ridge boards very easily. 



