In fig. 24 is given an illustration of a small detached house, in which the arrangement of the lightning conductor is indicated by the dark lines. The method followed is exactly the same in principle as that employed for the mansion just described. A terminal rod is placed upon each chimney. These terminal rods are connected with each other by a copper-rope conductor which is carried along the ridges and gables of the roof, thus constituting a similar arrangement to the French ‘ridge-circuit’ (_circuit des faîtes_), with the additional advantage of being far lighter and more sightly. The copper conductor descends to the earth down the angle formed by the projecting entrance to the house. By this means every corner of the building is protected; an important matter in all detached buildings, and especially when they happen to stand among trees. The preference of the electric force for trees as its path to the earth in the absence of metal or other bodies of higher conductivity than trees, has probably no other ground than their being full of moisture; still this is a disputed question.
Fig. 25 exhibits a slightly different method of arranging the lightning conductor. In this case the ridges of the roof are surmounted by ornamental iron-work, instead of the usual terra-cotta, or earthenware, tiles. This iron-work is utilised and carefully connected with the conductor. The chimneys, in place of being fitted with terminal rods, are provided with cast-iron caps--as shown in the engraving--to which the conductor is attached. The conductor, after descending to the ridge, is led along it and down the edges of every gable, and is finally carried down to the ground and connected with the earth in the usual manner. It is of course absolutely necessary that all masses of metal, such as gutters, waterspouts, rain-pipes, &c., should be brought into connection with each other and with the conductor, in order that the house may constitute one electrically homogeneous body.
It was for a long time held that the protection of churches against lightning offered special difficulties. This arose mainly from the constant reports of churches being struck, often when they were believed to be protected, whereas the accidents arose from the conductor not being properly fitted. It is even now too often forgotten that all so-called ‘conductors’ of the electric force are only so in relation to ‘non-conductors,’ and that, strictly speaking, all things on earth are to some extent conductors and to some extent non-conductors. This being kept clearly in view, there is no more difficulty in protecting the largest cathedral against lightning in the most efficient manner than in similarly guarding the smallest cottage.
