Lightning conductor

“ What is beyond controversy is, that a good conductor, in proper condition, is absolutely harmless to surrounding objects, including human beings. A man, even with a ‘fowling-piece’ in his hands, might lean full length against half-an-inch copper rod carrying off a heavy stroke of lightning into ‘good earth’ without so much as becoming aware of the passing of the electric discharge. ”

“ It may be laid down as an absolute fact, that a well-made lightning conductor, properly placed, and kept in an efficient state, can never, under any circumstances, fail in its action. Undoubtedly it has happened that buildings to which conductors were attached have, in many instances—of which some will be enumerated in another chapter—been struck by lightning, and even damaged; but these cases, so far from going against the truth that good lightning conductors are infallible, only serve to prove it. ”

“ In the first place, they laid it down as a hard-and-fast rule that the upper rod of a lightning conductor—that projecting over the roof—‘will be an efficient protective against lightning within the circular area of a radius double that of its height,’1 and the acquiescence in this supposed absolute formula had for one of its results the erection of monstrously huge rods, made to tower high above buildings, so as to increase the field of protection to the largest possible extent. ”

“ Lightning conductors are such every-day objects that no description is necessary; but the reason the lightning runs along it harmlessly is because the galvanized iron rod is the best conductor in the immediate neighbourhood. ”

“ He established the identity between the electric force and lightning, and upon it based one of the noblest inventions of all ages, that of the lightning conductor. And perhaps there never was any invention acknowledged more deeply by mankind. ”

“ Mischief Done by Bad Conductors.—If the earth contact is bad, a lightning conductor does more harm than good. It invites the lightning down upon the building without providing for it, at the same time, a free passage to earth. The consequence is that the lightning forces a way for itself, violently bursting asunder whatever opposes its progress, and setting fire to whatever is combustible. ”

“ From the above remarks, it will easily be seen that lightning conductors should be made of materials possessing the highest possible power of conductivity, and be large enough to carry off the heaviest electric discharge that is ever likely to fall upon them. The various metals being by far the best conductors of electricity, it follows that the lightning conductor must be constructed of metal of some kind. ”

“ Here, again, we have a good imitation of Professor Richman’s experiment, with only this difference, that a small hole in the rock is substituted for a glass bottle. A lightning conductor of this kind fulfills two functions: it increases the chance of the lightning coming down on the building, and it makes it positively certain that, having come, it cannot get to earth without doing mischief. ”

“ A close investigation of all known instances where the electric force has struck buildings, nominally protected against lightning, shows most conclusively that the conductors placed on them were either inefficient, in some way or the other, or did not lead properly into moist ground—that is, had not the all-indispensable ‘earth connection.’ There is no case on record in which a really efficient lightning conductor, properly placed, and with its terminal in technically so-called ‘good earth,’ did not do its duty ”

“ Franklin’s Lightning Rods.—The object of lightning conductors is to protect life and property from these destructive effects. Their use was first suggested by Franklin, in 1749, even before his famous experiment with the kite; and immediately after that experiment, in 1752, he set up, on his own house, in Philadelphia, the first lightning conductor ever made. ”

“ Height was sought where nothing but depth was required, and the same unsightly rods, towering high above buildings, would have very effectually carried off the electric forces if brought from the top to the bottom of the conductor, being taken out of the air and stuck into the earth. Still, there were not wanting philosophical minds impressed with the truth that no lightning conductor can discharge its functions unless rooted in moisture, and who not only knew it, but did their best to spread this knowledge in all directions. ”

“ This examination ought to be insisted on, as the earth connection is often wilfully destroyed; but I have never in all my experience known a building which had a conductor properly fixed to suffer damage from lightning.’
What is really required is to make a lightning conductor155 of sufficient calibre to carry down the electric discharge, however great it may be, from the summit of the building into the earth, and that the earth contact should be above suspicion and thoroughly good in all seasons. ”

“ In America, as elsewhere, the earth-terminal is regarded as of prime importance, and in all properly constructed lightning conductors receives the greatest care and attention. In the first place, such metal pipes as lead from the building to the water-mains, gas-mains, and sewers are carefully connected with the principal lightning conductor, in order that they may act as auxiliary earth-terminals. ”

“ As the use of metals, especially iron, in the construction of dwellings, both exterior and interior, is rapidly extending, this becomes a very important consideration in planning the design of lightning conductors. Of equal moment is a second point—that of the existence of water or great moisture under the buildings, or part of them. This must decide invariably the direction of the conductor towards the earth, and its depth underground. ”

“ EARTH PLATES.—This portion of the lightning conductor is of the utmost importance, but has hitherto been the most neglected. The majority of cases in which lightning has caused injury very near to or upon conductors are traceable to those conductors having imperfect earth terminals. We know of many cases in which the earth terminals have been miserably imperfect, or entirely neglected, when the above-ground portion has been perfectly satisfactory. ”

“ It is much to be regretted that not only professors and amateurs studying the manifestations of the electric force, but even learned societies, such as the French ‘Académie des Sciences,’ should have spread so many imaginative theories about this ‘reception rod.’ At the bottom of all was the fancy, not often declared, but still visible in its expression, of the metallic conductor possessing some occult power of attracting lightning. ”

“ Consequently, wherever trees are being planted, or growing up around houses, the greatest care should be taken in designing lightning conductors, so as to provide against the action exercised by them in juxtaposition to the electric force. Thus, if trees, originally small, should reach to such a height above dwellings as to make it possible that a stroke of lightning will fall upon them, in preference to the conductor, the arrangements for protection will have to be altered, so as to ensure the safety of the house nearest these particular trees. ”

“ It therefore appears proved that the discharges of electricity of high potentials obey the laws of Ohm, and are not affected by change of form. Hence, extent of surface does not favour lightning discharges. No more efficient lightning conductor than a cylindrical rod or a wire rope can therefore be devised. ”

“ The tramping ‘lightning-rod men’ of the United States are notorious for extortion and ignorance: they use all kinds of fantastic and peculiar shaped terminal rods and conductors,134 the main object being to make as great a show with as little metal as possible. Their work is almost entirely confined to the upper portion of the conductor, to the neglect of the most important part—the earth terminal. In consequence, the majority of the lightning conductors in America are untrustworthy ”

“ It is not, therefore, surprising that atmospheric electricity, of a tension sufficient to strike through a stratum of air several hundred yards thick, should find an easier path to the earth by leaping from a lightning-conductor through a few feet of air or stone to a great system of gas or water mains, extending in large towns for miles, than by the short line of metal extended in the ground which forms the usual termination of a lightning-conductor. ”

“ Modern experience has proved this to be an absurdity; still, in the infancy of all knowledge about lightning conductors it was, perhaps, not unnatural that even learned men should believe in such fancies. Lightning was looked upon, not only in name but in reality, as an electric ‘fluid’ and the conductor was supposed to102 draw this ‘fluid’ from the clouds. ”

“ The discharge sometimes takes place from the earth to the cloud, or from a lower to a higher stratum, and sometimes from conductors silently. Rain discharges the electricity quietly to earth, and lightning frequently ceases with rain (see Atmospheric Electricity) .
LIGHTNING CONDUCTOR, or Lightning Rod (Franklin) , the name usually given to apparatus designed to protect buildings or ships from the destructive effects of lightning (Fr. paratonnerre, Ger. Blitzableiter) . ”

“ I had, moreover, beside me a portion of a chain cable through which a lightning discharge had passed, the electricity in passing from link to link encountering a resistance sufficient to enable it to partially fuse the chain. The abolition of resistance is absolutely necessary in connecting a lightning conductor with the earth, and this is done by closely embedding in the earth a plate of good conducting material and of large area. The largeness of area makes atonement for the imperfect conductivity of earth. ”

“ Franklin found he could not destroy a wet rat by artificial electricity, although he could a dry one.
The first lightning conductor was erected in England at Payneshill, by Dr. Watson, in 1762.
The lightning conductor should expose a large surface, and should be united with all the great masses of metal in its vicinity. For stationary elevations the conductor should consist of solid or tubular rods or flat plates of metal. We must consider the mechanical action (86) the lightning may produce on the conductor, as well as any possible heating action. ”

“ He lastly considers the question, formerly much debated as to whether a lightning rod attached to a house will attract to the house a discharge that otherwise would not have struck it, and he concludes that there is no foundation for the erroneous impression that the existence of a lightning conductor can ever cause damage. ”

“ It is the old delusion that a lightning conductor need be brought down underground only, and that then all is right. In this case, those who protected Christchurch, Clevedon, thought it quite sufficient to bring the conductor down into a drain-pipe carrying rain-water from the roof, without reflecting for210 a moment that an earthenware drain-pipe would insulate the conductor from ‘earth.’ A similar instance came under the writer’s notice about a year ago. One of the pinnacles of Cromer Church, in Norfolk, was struck by lightning, although fitted with a conductor on one of the pinnacles. ”

“ A warm flue, terminating in a metal grate, is a dangerous conductor, as it ends in the room and not in earth: hence so many accidents indoors. A lightning conductor should expose a prominent metallic point, and offer a path of little or no resistance thence to earth. ”

“ This method possesses several advantages; it is very sightly and neat, it can be easily applied without injury to any building, and as it allows the conductor a certain freedom of movement, it readily permits the contraction and expansion caused by the variations of temperature. The band conductor shown here is one inch wide by one-eighth of an inch thick, and weighs ·44 pound per foot. The rope conductor, although it appears less, has more metal in it; it measures five-eighths of an inch in diameter, and weighs ·67 pound. Fig. 33 shows a different mode of attaching the lightning conductor. ”