Probably, the matter was more studied by Italian scientific men than any others, the study of electricity having always been a favourite pursuit in that country; yet there, too, the matter was not understood till quite recently. This is proved by a letter of the celebrated astronomer and meteorologist, Father Secchi, addressed to the French scientific journal ‘Les Mondes,’ in October 1872, in which he tells the story of an accident that befel a building protected by lightning conductors set up under his own direction, the earth connection being made after rules laid down by Professor Matteucci, considered the leading authority on the subject. The letter of Father Secchi, though of some length, is given here entirely, both on account of the great fame of the writer, but recently deceased, and because it throws a flood of light on some of the most important points connected with the art of designing and applying lightning conductors.
‘Eight years ago,’ says Father Secchi, writing, as just mentioned, in 1872, ‘some lightning conductors had been erected under my direction on the cathedral and on the Bishop’s palace of Alatri, situated at the summit of the Acropolis of that town, which, by its elevated and solitary position, was exposed to frequent ravages from storms. It was not long ago that a flash of lightning demolished a great part of the belfry, and damaged the organ of the church. In the erection of this lightning conductor there arose a great difficulty proceeding from the nature of the soil, which at the depth of some centimetres turns out to be entirely of solid calcareous rock.
‘In order to remedy this defect, that part of the conductor which enters the ground has been made very long, more than 4 metres [13 feet], and has been provided with a great many couples of points, 5 centimetres [2 inches] broad, 5 millimetres [⅛ inch] thick, indentated on the edges, with the addition of a thick copper wire twisted among the same points, to help to multiply the points of contact between the rod and the carbon. The foot of the lightning conductor is entirely of copper. The rod is also of copper up to a metre [3¼ feet] above the ground; and there is joined to it the iron conductor, in the ordinary receptacle made in the heart of the wall, to preserve it from disturbances of the inferior parts. The ditch into which the foot of the lightning conductor was sunk is 5 metres [·16 feet] long, and half-a-metre [1⅝ feet] wide, and it was dug into the ground as far as to touch the roots of some neighbouring trees, from which point upwards a layer of cinders was placed, covering the greater part of the ditch. Thus the surface of contact between the metal and the carbon, and of the latter with the soil, was such that one would have supposed it to be more than sufficient, while the presence of trees, although they were not very large, made it highly probable that the ground did always contain sufficient moisture. Moreover, as the edifice had two culminating points--namely, the belfry and the raised back portion of the choir--two rods were placed on them, each having an independent connection with the earth, so that, in the case of a discharge on one of the points, the electric force might find two ways in its course towards the earth.