Before quitting the French system, mention should be made of a novel form of lightning conductor devised by M. Jarriant. This gentleman proceeds on the hypothesis that the most essential requisites of a lightning conductor are:--a terminal rod metallically homogeneous, which should rise to a good height; that it be sufficiently light to avoid damage to the roof, and yet be strong enough to resist the violence of the wind. To attain these requirements, M. Jarriant secures his conductor with three or four stays, which are firmly fixed to the roof and converge to the top of the terminal rod, to which is fastened the ordinary copper point, recommended in the ‘Instruction’ of the Academy of Sciences. Iron supports are placed at different heights in order to ensure the perfect solidity of the system. Galvanised iron is employed, and all the various stays and supports are metallically connected with each other. The angles of the irons are all acute, and placed so as to offer the least resistance to the wind. The advantages claimed for this method are that the upper part of the conductor bristles with spikes and aigrettes, which he considers a great advantage in regard to the preventive effect produced by the conductor; it allows of the conductor being raised much higher above the building; it presents a large surface to the electrified cloud; the joints are so arranged that they cannot be dislocated by the expansion and contraction caused by variations of temperature; and, lastly, it is affirmed that these conductors cost thirty per cent. less than those erected under the ordinary system.
America stands pre-eminent above other countries in the numerous and extraordinary schemes that have there been promulgated in regard to the protection of buildings from the effects of lightning, and probably no other nation has been so systematically victimised and swindled in this matter. 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, 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; very often they are practically insulated from the ‘common reservoir’ or subterraneous water, and are therefore more often a source of danger than a protection. Unhappily, these peripatetic mechanics are by no means extinct, although increased knowledge is gradually driving them from the field.