Faraday to Jacob Herbert   27 September 1852

Royal Institution, | 27th September, 1852.

My dear Sir,

I fortunately reached the Nash Low Lighthouse¹ last Thursday², before any repairs were made of the injury caused by the discharge of lightning there, and found everything as it had been left: the repairs were to be commenced on the morrow.

The night of Monday, 30th August, was exceedingly stormy, with thunder and lightning; the discharge upon the lighthouse was at six o’clock in the morning of the 31st, just after the keeper had gone to bed. At the same time, or at least in the same storm, the flagstaff between the upper and lower lights was struck, and some corn stacks were struck and fired in the neighbourhood. It is manifest that the discharge upon the tower was exceedingly powerful, but the lightning conductor has done duty well - has, I have no doubt, saved the building; and the injury is comparatively slight, and is referable almost entirely to circumstances which are guarded against in the report made by myself and Mr. Walker 22nd September, 1843³.

The conductor is made fast to the metal of the lantern, descends on the inside of the tower to the level of the ground, and passes through the wall and under the flag pavement which surrounds the tower. It is undisturbed everywhere, but there are signs of oxidation on the metal and the wall at a place where two lengths of copper are rivetted together, which show how great an amount of electricity it has carried.

A water-butt stands in the gallery outside the lantern. A small copper pipe, 1 inch in diameter, brings the water from the roof of the lantern into this butt; it does not reach it, but terminates 10 or 12 inches above it. A similar copper pipe conducts the surplus water from the butt to the ground, but it is not connected metallically with the other pipe, or with the metal of the conductor, or the lantern. Hence a part of the lightning which has fallen upon the lantern has passed as a flash, or, as we express it, by disruptive discharge from the outside of the lantern to this tub of water, throwing off a portion of the cement at the place, and has used this pipe as a lightning conductor in the rest of its course to the ground. The pipe has holes made in it in three places, but these are at the three joints, where, it being in different lengths, it is put together with tow and white lead, and where of course the metallic contact is again absent; and thus the injury there (which is very small) is accounted for. The pipe ends below at the level of the ground in a small drain, and at this end a disruptive discharge has (naturally) occurred, which has blown up a little of the cement that covered the place. Some earth is thrown up at the outer edge of the pavement round the tower over the small drain, which tends to show how intense the discharge must have been over the whole of the place.

Instead of the lantern there are traces of the lightning, occurring at places where pieces of metal came near together but did not touch, thus at the platform where a covering copper plate came near to the top of the stair railing, but the effects are very slight. All the lamps, ventilating tubes, &c., remained perfectly undisturbed, and there was no trace of injury or effect where the conductor and the lantern were united.

Inside of the tower and the rooms through which the conductor passes there were and are no signs of anything (except at the rivetting above mentioned) until we reach the kitchen or living-room which is on a level with the ground, and here the chair was broken and the carpets and oil-cloth fired and torn. To understand this, it must be known that the separation between this room and the oil-cellar beneath is made by masonry consisting of large stones, the vertical joints of which are leaded throughout, so that the lead appears as a network upon the surface, both of the kitchen floor above, and the roof of the oil cellar beneath, varying in thickness in different places up to 1/3 or more of an inch, as in a piece that was thrown out. The nearest part of this lead to the conductor is about 9 inches or a little more distant, and it was here that the skirting was thrown off, and the chair broken; here also that the fender was upset and the little cupboard against the skirting emptied of its articles. If this lead had been connected metallically with the conductor, these effects would not have happened.

The electricity which in its tendency to pass to the earth took this course, naturally appeared in the oil-cellar beneath, and though the greater portion of it was dissipated through the building itself, yet a part appeared in its effects to have been directed by the oil cans, for though they were not at all injured or disturbed, the wash or colour in the wall above four or five of them was disturbed, showing that slight disruptive connections or sparks had occurred there.

At the time of the shock, rain was descending in floods, and the side of the tower and the pavement was covered with a coat of water. This being a good conductor of electricity has shown its effects in connection with the intense force of the discharge. A part of the electricity leaving the conductor at the edge of the pavement and the tower, broke up the cement there, in its way to the water on the surface, which for the time acted to it as the sheet of copper - which I conclude is at the end of the conductor - does, i.e., as a final discharge to the earth. Also on different parts of the external surface of the tower near the ground, portions of cement, the size of half a hand, have been thrown off by the disruptive discharges from the body of the tower to this coat of water: all testifying to the intensity of the shock.

I should state that the keeper says he was thrown out of bed by the shock. However, no trace of lightning appears in the bedroom, still there are evidences that powerful discharges passing at a distance, and on the other side of the thick walls may affect bodies and living systems, especially by spasmodic action, and something of the kind may have occurred here. It may be as well for me to state that the upper floors are leaded together like that of the kitchen. The reason why they did not produce like effect is evident in that they from their position could not serve as conductors to the earth as the lower course could.

The keeper said he had told the coppersmith to make the necessary repairs in the pipe, and I instructed him to connect the waste pipe and the upper pipe by a flat strap of copper plate. I would recommend that the lead of the lower floor be connected metallically with the conductor to a plate of copper in the earth. I could not see the end of the present conductor, not being able by any tools at the lighthouse to raise the stonework, but I left instructions with the keeper to have it done, and report to me the state of matters.

I am, &c., | (signed) M. Faraday

The Secretary, | Trinity House.