10 Construction and Erection of 



In absence of such earth connections the conductor should 

 terminate in a large plate or coil of wire buried sufficiently 

 deep in a permanently moist stratum, and will be best if 

 surrounded by coke or charcoal, which are absolutely 

 imperishable materials of relatively high conductivity, and 

 therefore well-suited for distributing the electrical discharge. 

 There should be several of such earth plates, even to one 

 conductor, which can be arranged by joining two or three 

 such connectors to the conductor before entering the earth. 



To summarise this part of the subject it may be laid 

 down that "A good and extensive earth connection is of 

 paramount importance" 



From the earth to the higher parts of the building the 

 conductor may assume almost any form of a continuous 

 metallic path. Iron rod, wire rope, sheet metal, pipes, or 

 anything of the kind so long as it be large enough and 

 metallically continuous ; mere contact of one piece of pipe 

 or rod with another is dangerous — they must be joined by 

 solder ; thus down pipes and ridging metal may be quite 

 safe to use if every joint is soldered over a large surface : no 

 lapping, however extensive, will do. Whatever be used 

 must take the form of a continuous metal connection with 

 the earth. 



It is unnecessary, and in fact wrong, to insulate the con- 

 ductor from any part of the building at all ; it should lay on 

 the roof, along the gutters, or anywhere convenient, and 

 pass down the walls at any convenient place, and be kept 

 in position by any ordinary hold-fasts. 



The upper projecting-rod of a lightning-conductor need 

 never be more than three to five feet above the highest 

 portion of the building to be protected, and should termi- 

 nate in a single point, which it is better to make of a metal 

 not liable to rust, and as most projectives of conductors will 

 be of iron, a good copper point, stoutly gilt, well brazed to 

 the iron, will be found the most economical and effective. 



From experiments conducted by the French Academy of 

 Sciences it is considered that the area protected by a single 

 lightning conductor is about equal to twice the radius of its 

 height ; therefore, if a conductor were a hundred feet high, 

 it would protect a building covering an area of 100 feet 

 radius ; but half this is now generally taken as the safest 

 proportion, and, therefore, a conductor 100 feet high would 

 protect a building of fifty feet radius. The lower the con- 

 ductor the less area it will protect, so that a low straggling 



