THE HOUSE AND ITS EOl II .MENT. 127 



LIGHTNING CONDUCTORS. 



duiscs of Lightning Popular Scepticism Alton! Conductors IVr.v.v &amp;lt;&amp;gt;j Sir (Hirer l.ody The 

 &quot; ( &amp;lt;, &amp;lt; &quot; Svslcin Copper remits (idlrtiniscd Iron Sa/c/v in a Stonn. 



Til XDER and lightning have been tin. most universally awe-inspiring of Nature s phenomena 

 in all ages of the world, and lightning was, undoubtedly, tin 1 first manifestation of electricity 

 to hi voiiclisali d to man. Tins being so, it seems strange that in thoe days of advanced 

 electrical research there should he so little positive knowledge available concerning it. 

 Lightning was not identified with electricity until the eighteenth century, and in the twentieth 

 we cannot better protect our buildings from the ravages of the lightning stroke than by following the 

 precepts of Franklin as elaborated by Maxwell. Maxwell in this, as m other matter-, has proved liimsell 

 the greatest of electrical prophets, his proposed modifications ot Franklin s isolated lightning rods into 

 a network of conductors running along the angles ot a building bein.i; very much on the lines of the latent 

 recommendations of the Lightning Re-search Committee. 



There does not yet appear to be any general concensus ot opinion anionn those who have studied 

 the question as to how the clouds acquire a charge of electricity sufficiently great to cause repeated 

 lightning Hashes sometimes as much as two miles long. Recent research into the electrical conditions 

 at high altitudes shows that the air there is electrically charged. In that case, the theory that it is the 

 coalition of minute particles ot vapour, ultimately forming raindrops, which cause-- the high charge oi 

 electricity in a thunder-cloud, would seem to be a feasible one. The minute vapour particles have a much 

 larger superficial area in the aggregate than tin raindrop which contains many ol them, and as the electrical 

 charge resides entirely on the surface, there is less room tor any given quantity ot electricity alter the 

 coalescence has taken place than there was before, and consequently the potential of the charge is greatly 

 increased. It also seems to be proved that the light and heat of the sun to some extent electrically charge 

 the bodies on which they fall directly, and that the interposition ol a cloud annuls this ellect. It is, 

 therefoie, possible to assume this to be one of the contributory causes ol a thunder-cloud. Cyclonic winds 

 with horizontal axes, which are assumed to act in the manner of a trictional electrical machine, and 

 other natural phenomena, have at one time and another been pressed into the service of lurnUhiiig 

 explanations of the electrical charge. Whichever of the above theories may be the true one, and it is quite 

 possible that all are true to some extent, it is to the avoidance of damage to life and property that the 

 designers of lightning conductors must address themselves ; and the problem is a difficult one on account 

 of the cataclysmic nature of the lightning stroke. During the short period that it lasts many thousands 

 of horse-power have to be dissipated, and this must be done harmlessly. 



The fact that a building protected by lightning conductors is occasionally struck has given rise to 

 a certain amount of popular scepticism as to their utility. This is unfortunate if it leads anyone to 

 neglect this means of protection, which, if properly carried out, is undoubtedly a very great safeguard, 

 though never an absolute specific against the ravages of the storm. Perhaps the following analogy may 

 help the non-technical reader to an understanding of the matter : Supposing that all the culverts which 

 run through a railway embankment for the purpose of conveying away the surface drainage water were 

 suddenly called upon to deal with a flood caused by a bursting reservoir. They would obviously be 

 incapable of doing it as designed at present, and though they would ultimately carry away all the water, 

 some slight damage might be caused. Suppose, further, that the bursting of the reservoir was a more 

 or less frequent occurrence, and culverts were designed to meet the case. They would have to be .it 

 enormous size to be capable of dealing with such a cataclysmic contingency. It may be asked,&quot; Is it, 

 then, merely a question of making the lightning conductor big enough 5 No ! for if we pursue our 

 analogy still further, and assume that there is a row of cottages facing our railway embankment on the 

 lower side, we find that while these would suffer little if the culverts through the embankment were of 

 normal size, they might be altogether swept away if large culverts capable of dealing with the flood had 

 been put in. So it is with the lightning conductor ; a large conductor is rather a source of danger than 

 otherwise. A flash of lightning develops enormous energy, and this must be got rid of. It cannot be 

 conjured out of existence by conducting it too easily to earth ; in that case it will run up again, surging 

 backwards and forwards many times, before it finally dies away, and may do much damage in the process. 

 Sir Oliver Lodge, who has perhaps been more active in lightning research than any other scientist 

 in this country, divides lightning strokes into two classes Class A, when a cloud becomes highly charged 



