From out of the almost endless number of cases in which lightning conductors failed for want of a good earth connection, another one or two may be given, illustrated as having happened quite recently in England, and as such showing, in a very striking manner, in what a neglected state the knowledge of the subject still is at this moment. A thunderstorm passed over the town of Clevedon, Somersetshire, in the afternoon of March 15, 1876, and a flash of lightning fell upon the steeple of Christchurch, provided, as was generally thought, with a most efficient conductor of recent construction, made of good copper rope. What happened is graphically and minutely told in a letter addressed to the ‘Journal of the Society of Telegraph Engineers,’ by Mr. Eustace Buttor, of Lewesfell, near Clevedon. ‘There was but a single flash,’ Mr. Buttor relates, ‘which appeared to many observers to travel horizontally through the air. However, the lightning passed down the lightning conductor of Christchurch. The flag-staff, about 100 feet high, and the four pinnacles, about 90 feet high, have each a conductor, the flag-staff having the usual conical point, the pinnacles having the copper rope attached to their vanes. The five copper ropes unite inside the tower in the neighbourhood of the clock. Lower down the conductor passes through a slanting hole to the outside, and for the lowest 12 feet is encased in a pipe. On reaching the ground it passes into a dry freestone channel for about a dozen feet, and then dips down into the drain which carries rain-water from the roof. As no rain preceded or accompanied the flash, it may be presumed that _the drain was dry_.
‘The protector is copper throughout, and, with the exception of the termination, seems to have been carefully and efficiently placed. The diameter I estimate to be half-inch, or it may be a trifle more. Just at the point where it leaves the pipe and enters the ground, the electric charge left it, dashed through three feet or more of solid wall supporting the tower, in order to reach the gas-meter inside, then it passed safely along the gas-pipe. The cavity made was considerable, but very irregular. I was unable to ascertain when the workmen were engaged in repairs, and therefore cannot give their estimate of the weight of stone displaced, but it must have been many hundredweights, though only a few pounds were actually thrown out on to the path, or inside into the vault. A large quantity of stone was pulverised, and the whole gave one the idea of the explosion of a charge of gunpowder under great compression. In a house about 100 yards from the church, the inmates felt the shock intensely, but did not know that the house had been touched. Some hours after, however, on going to turn on the gas, a hissing noise was heard, and a hole was found in the composition gas-pipe, about five-eighth inch diameter, just where the pipe passed within an inch of a water-pipe. The lightning must have come along the main from the church gas-pipe to this house, and then passed to the water-pipe as the readiest way to moist earth. The whole soil in the neighbourhood is mountain limestone, very dry. There is not the slightest evidence of displaced plaster, or any other sign of the passage of an electrical discharge through the house.’ There need be little comment on the facts stated in this letter, notable though they are. It is the old delusion that a lightning conductor need be brought down underground only, and that then all is right. In this case, those who protected Christchurch, Clevedon, thought it quite sufficient to bring the conductor down into a drain-pipe carrying rain-water from the roof, without reflecting for a moment that an earthenware drain-pipe would insulate the conductor from ‘earth.’ A similar instance came under the writer’s notice about a year ago. One of the pinnacles of Cromer Church, in Norfolk, was struck by lightning, although fitted with a conductor on one of the pinnacles. On examination it was discovered that the earth terminal had been inserted into an earthenware drain.