220 LIGHTNING CONDUCTORS. 



appearance in the case of ordinary buildings and the multiplica- 

 tion of points, even of the short pattern now advocated, cannot 

 be carried to excess. Prominent ridges should be provided with 

 one for every fifteen or twenty feet of length ; every corner 

 should also have its point and all should be connected together 

 and to the " earth." 



10. This connecting up of points results in a net-work over 

 the whole roof which forms the nearest feasible approach to 

 the continuous metallic screen held by modern views to con- 

 stitute an absolute safeguard. 



11. As suggested in paragraph 7 the down pipes from rain 

 guttering may frequently be used for bringing down the wires 

 from roof net- work to earth. The connection to roof net-work 

 should be made by inserting the wire into a corner point, 

 where it will meet two net- work wires. Soldered joints will 

 still be unnecessary as the wires will be in close contact through- 

 out the length of the point. 



12. The question of earth connection has next to be con- 

 sidered. This is usually held to be of primary importance and 

 various rules are laid down which state the exact maximum 

 resistance permissible. It is, no doubt, desirable that the resis- 

 tance should be reasonably low so that disturbance may be avoid- 

 ed, but whether it be of two ohms or fifty matters very little. 

 The effect of a poor earth connection was recently demonstrat- 

 ed at the Civil Prisons in Singapore, where a discharge taken 

 by the conductor blew out the soil over the earth connection, 

 leaving a hole about three feet in diameter and two deep. This 

 earth was formed of the coiled end of the conductor — a heavy 

 galvanised iron cable — and was buried to a depth of a couple 

 of feet only, on a slope. Moist soil would have been reached 

 by taking it a little further away to lower ground and burying 

 it a little deeper, but, on enquiry, the writer found that the 

 workman responsible bad miscalculated the length required, 

 cut the cable and hurriedly buried the end. The instance 

 serves to show that no great harm results from imperfect earth 

 connections if they are placed sufficiently far from foundations. 



13. It is rarely a matter of great difficulty or expense — es- 

 pecially where galvanised iron is the material used — to con- 

 tinue the conductor to permanently damp earth. If it is laid 



Jour. Straits Branch 



