5.--All this plainly teaches us, that in order to guard a building effectually against damage by Lightning, we must endeavour to bring the general structure as nearly as may be, into that passive or non-resisting state it would assume, supposing the whole were a mass of metal.
6.--To this end, one or more conducting channels of copper depending upon the magnitude and extent of the building should be systematically applied to the walls; these conducting channels should consist either of double copper plates united in series one over the other, as in the method of fixing such Conductors to the masts of Her Majesty’s Ships, the plates being not less than 3¹⁄₂ inches wide, and of ¹⁄₁₆th and ¹⁄₈th of an inch in thickness, or the Conductors may with advantage be constructed of stout copper pipe not less than ³⁄₁₆ths of an inch thick, and 1¹⁄₂ to 2 inches in diameter: in either case the Conductors should be securely fixed to the walls of the building, either by braces, or copper nails, or clamps; they should terminate in solid metal rods above, projecting freely into the air, at a moderate and convenient height above the point to which they are fixed, and below they should terminate in one or two branches leading outward about a foot under the surface of the earth; if possible, they should be connected with a spring of water or other moist ground.
It would be proper in certain dry situations, to lead out in several directions under the ground, old iron or other metallic chains, so as to expose a large extent of metallic contact in the surface of the earth.
7.--All the metals in the roof and other parts of the building of whatever kind, should so far as possible have metallic communication with these Alarm Conductors, and in case of any prominent elevated chimney, it would be desirable to lead a pointed conducting tube along it to the metals of the roof; all of which satisfies the conditions above specified.
8.--Remark 1.--It is now proved beyond all questions, that the electrical discharge never leaves perfect conducting lines of small resistance, in order to pass out upon bad conducting circuits, in which the resistance is very great, that is an established law of nature; hence a stroke of Lightning upon such conducting lines will be confined to the Conductors as constituting a line of discharge of less resistance than any other line of discharge through the building, which can be assigned. The apprehension of “Lateral Discharge” therefore, from the Conductor, is quite absurd; and is not countenanced by any fact whatever; if any doubt could possibly exist, it would be now most completely set at rest by the experience of the permanent Conductors, applied to the masts of Her Majesty’s ships. In very many instances furious discharges of Lightning have fallen on the masts with a crash as if the ship’s broadside had been fired, and the solid point aloft has been found melted; in all these cases electrical discharge robbed by the Conductor of its explosive violence, has traversed the line of action to the sea, through the ship, and through the copper bolts, driven through the ship’s solid timbers, without the least damage to the surrounding masses, whether metallic, as in the case of the massive iron hoops on the lower masts, or not. Persons have either been close by or actually leaning against the Conductors at the time, without experiencing any ill consequence.