The information thus spread by the French Government gave rise to important results. It caused the setting-up of lightning conductors throughout the country, on private as well as public buildings, and it likewise led to an improved construction of them, in as far as the ‘Instruction’ recommended the rods to be made of stout pieces of metal, well fastened to each other, and, above all, led into the ground deep enough to reach moist earth or water. If this was well enough, and useful enough, to meet with general acceptation, there were some points in the advice of the learned men of the ‘Académie’ that gave rise to much criticism, as being more founded upon theory than practical experience. In the first place, they laid it down as a hard-and-fast rule that the upper rod of a lightning conductor--that projecting over the roof--‘will be an efficient protective against lightning within the circular area of a radius double that of its height,’[1] and the acquiescence in this supposed absolute formula had for one of its results the erection of monstrously huge rods, made to tower high above buildings, so as to increase the field of protection to the largest possible extent. Another and worse fault was committed by the authors of the ‘Instruction’ in not saying anything about the necessity of regularly inspecting the actual condition of lightning conductors, and testing them in respect to their efficiency. While giving minute advice as to the mode of construction and the general design of conductors, the contents of the ‘Instruction’ were such that, on the whole, its readers would take it for granted that it was only necessary to properly join the strips of metals and bring them down into the ground, after which, thenceforth and for ever, the protection against lightning would be complete. This grave omission, together with the erroneous dogma as to absolute rule of protection within an area prescribed by the height of the ‘tige,’ or upper part of the rod, had the inevitable result of causing disasters, and before the ‘Instruction’ had been issued many years, there came report after report to the
[1] The original, long taken as a scientific dogma, runs: ‘Une tige de paratonnerre protège efficacement contre la foudre autour d’elle un espace circulaire d’un rayon double de sa hauteur.’