114 On Lightning Conductors. 



7. Mateeial for Kod. — Copper, weighing not less than 

 6 oz. per foot run, and the conductivity of which is not 

 less than 90 per cent, of that of pure copper, either in the 

 form of tape or rope of stout wires, no individual wire 

 being less than No. 12 B.W.G. Iron may be used, but 

 should not weigh less than 2 J lbs. per foot run. 



8. Joints. — Although electricity of high tension will 

 jump across bad joints, they diminish the efficiency of the 

 conductor ; therefore every joint, besides being well cleaned, 

 screwed, scarfed or riveted, should be thoroughly soldered. 



9. Protection. — Copper rods to the height of 10 feet 

 above the ground should be protected from injury and 

 theft by being enclosed in an iron pipe reaching some 

 distance into the ground. 



10. Painting. — Iron rods, whether galvanised or not, 

 should be painted; copper ones may be painted or not 

 according to architectural requirements. 



11. Curvature. — The rod should not be bent abruptly 

 round sharp corners. In no case should the length of the 

 rod between two points be more than half as long again 

 as the straight line joining them. Where a string course 

 or other projecting stone work will admit of it, the rod 

 may be carried straight through, instead of round the 

 projection. In such a case the hole should be large enough to 

 allow the conductor to pass freely and allow for expansion. 



12. Extensive Masses of Metal. — As far as practicable 

 it is desirable that the conductor be connected to extensive 

 masses of metal, such as hot-water pipes, fee, both internal 

 and external ; but it should be kept away from all soft metal 

 pipes, and from internal gas pipes of every kind.* Church 

 bells inside well-protected spires need not be connected. 



13. Earth Connection. — It is essential that the lower 

 extremity of the conductor be buried in permanentl}^ damp 

 soil ; hence proximity to rain-water pipes and to drains is 

 desirable. It is a very good plan to make the conductor 

 bifurcate close below the surface of the ground, and adopt 

 two of the following methods for securing the escape of the 

 lightning to the earth. A strip of copper tape may be led 



* It is recommended that the inlet and outlet pipes of large gas-meters be 

 electrically connected together independently of the meter. The absence of 

 this precaution has led to accidents in two very remarkable eases. 



