There has been much controversy as to whether it is better to carry the conductor from the roof to the ground inside a building than outside the walls. As a matter of fact, it is a question of very small importance which way the conductor is carried, so long as it arrives at the ground by the shortest possible route. Benjamin Franklin, to judge from many expressions in his works, seems to have been decidedly in favour of the inside plan, which was adopted almost universally in France and on the Continent in general on the first introduction of lightning conductors. But the method was soon abandoned, owing partly to a witty saying of Voltaire, constantly quoted to this day. Speaking of the death of the unfortunate Professor Richman, of St. Petersburg, killed while experimenting with electric discharges from the clouds, Voltaire remarked, ‘There are some great lords whom one should only approach with extreme precaution: lightning is such a one.’ A mere jocular exclamation, it would have had no great force except in France, where a _bon mot_ may cause the fall of a king and the dethronement of a dynasty. In regard to Voltaire’s pleasantry about not approaching too close to lightning, it really had in great part the effect of preventing conductors to be laid inside the houses. Even such calm philosophers and men of science as Professor Arago quote Voltaire with approval. ‘I feel inclined,’ he remarks in his ‘Meteorological Essays,’ ‘to admit that the illustrious author (Voltaire) may be right, when I remember a case that occurred in the United States.’ The case relied upon, a very curious one, was as follows, in Arago’s own words.
‘Lightning,’ Professor Arago tells his story, ‘having struck a rather thick rod erected on a Mr. Raven’s house, in Carolina, United States, afterwards ran along a wire carried down the outside of the house to connect the rod on the roof with an iron bar stuck in the ground. The lightning in its descent melted all the part of the wire extending from the roof to the ground-storey, without injuring in the least the wall down which the wire was carried. But at a point intermediate between the ceiling and the floor of the lower storey things were changed: from thence to the ground the wire was not melted, and at the spot where the fusion ceased the lightning altered its course altogether, and, striking off at right angles, made a rather large hole in the wall and entered the kitchen. The cause of this singular divergence was readily perceived, when it was remarked that the hole in the wall was precisely on a level with the upper part of the barrel of a gun which had been left standing on the floor leaning against the wall. The gun barrel was uninjured, but the trigger was broken, and a little further on some damage was done in the fire-place.’ Commenting upon this case, Professor Arago goes on: ‘Here the lightning went off horizontally through the wall, in order to strike a fowling-piece standing upright in the kitchen. How much injury might not have resulted from this lateral movement, if the lightning had not had to traverse a thick wall?’ Consequently, he argues, Voltaire is right in his jocular-oracular declaration about the perils of indoor lightning conductors, in their being ‘great lords’ dangerous to approach.