‘These arrangements produced, on the whole, a good result, since, although the edifice was struck at least four times after conductors had been placed on it, it suffered no damage of any kind. Nevertheless a very curious accident, highly interesting as a scientific study, happened on October 2. Early on the morning of this day several flashes of lightning fell down from the clouds during a terrific storm, which lasted over two hours. The belfry was struck at first by weak discharges twice; but the third flash was so appalling in its strength as to terrify the whole town below. The injuries it caused were not great, still they seemed to me to be extremely noteworthy. But before I describe them I must give some necessary details as to place and position of the lightning conductor.
‘It so happened that four years after the erection of the conductor a line of pipes was laid down to carry water to the towns of Alatri and Ferentino, passing at a short distance from the belfry of the cathedral. The lightning conductor was not placed in communication with the pipes, because it seemed established, from previous experiments and observations, that it was needless to do so, the ground containing apparently sufficient moisture, the head of the waterworks being close, and there existing also a running fountain. I was not asked at the time whether it was necessary to establish this communication, but, had the question been put to me, I should probably have answered it in the negative, considering, from what I then knew, the work as superfluous. That I was in error then as to the necessities of a perfect underground connection is shown by what happened during the great storm in the early morning of October 2. The heavy flash of lightning before referred to did not go its appointed path underground, but passed off into the waterworks, with the following results:—
‘1. It made in the earth a perfectly rectilinear excavation, which, from the lower part of the conductor, went to the tube of the waterworks running to Ferentino, and in traversing the wall destroyed the angle of that structure. The earth of the ditch thus dug was disposed regularly to right and left with great symmetry. The length of the ditch was about 10 metres, the depth about 70 centimetres [28 inches].