Together with Dr. Hemmer in Germany, Professor Landriani, of Milan, drew attention to the paramount importance of a perfect earth connection. He made it his special business to investigate cases in which buildings with lightning conductors had been struck, and was able to show in nearly every instance that it had been for want of ‘good earth.’ A very striking case, which ought to have brought conviction of the truth to all investigators of the subject, occurred in Genoa in 1779. The church of St. Mary in this city, standing in a very elevated position, had been frequently struck by lightning, sometimes as often as twice in one year, and it was noticed that the electric force always followed precisely the same path, running along a certain portion of masonry, partly secured by iron hoops, and finally demolishing a wall at the bottom to get into the earth. At last, in November 1778, a conductor, made of the most approved design, was placed over the church, but, to the great surprise of the scientific men who had superintended the work, the lightning fell once more upon the building in the month of July of the following year, again following the old path it had constantly taken before, and causing absolutely the same damage as previously, even to the knocking out of certain portions of the wall nearest the ground. Naturally, the event caused widespread interest, leading to the closest examination of the church of St. Mary by several experts, among them Professor Landriani. He had no great trouble in discovering both the causes of the path of the lightning having always been the same when falling upon the church, and of the edifice having been struck again in the same manner when provided with a lightning conductor. Being a somewhat peculiar structure, consisting in part of hewn stones held together with iron cramps, there was a large quantity of metal both in and outside; and it was found that the path of the lightning had always been precisely in the direction where the metal offered the greatest continuity, leaping over the short intervals that existed by destroying the stone, and finally getting into the ground to a place where there was always a collection of water by knocking down a wall. If this accounted satisfactorily for the former accidents, that which took place when a conductor had been placed was not much more difficult of explanation. Professor Landriani found that though the conductor itself was very good, it was useless simply by having its roots in hard rock instead of moist ground. On the one side of St. Mary’s Church there was a rill of water rippling down from the hills, and forming a small pool near the church, while on the other was the hard rock. It was into a crevice of the latter that the conductor had been laid, thus leaving the electric force to seek its old path into the water along the iron bars, which, although disjointed, formed a far better road to earth than the planned road. It was a convincing proof of the supreme necessity of a good earth connection. Still, a long time yet was to elapse before conviction became general.