 
Selected accidents.I.About a quarter past ten p.m. on Aug. 14, 1857, an occurrence took place at the Brick-lane station of the Chartered Gas Company, St. Luke’s, which caused some alarm. It appears that the lightning struck one of the iron columns which supported one side of a gasometer, or gas holder, situate on the right hand side of the yard. Owing to the column having been thus struck by lightning, the gas, comprising many hundred thousand feet, became ignited. Fortunately, the services of the firemen were not required, for, owing to the admirable directions given by Mr. Upward, the superintendent of the works, and the exertions of the men under him, the flames were subdued in a comparatively short period. Fortunately no person was injured, and no damage was done to any of the surrounding property. II.At half-past eleven on Aug. 14, 1857, there was a terrific discharge of lightning, by which the south-east pinnacle of St. Michael’s Church, Stamford, was instantaneously struck down. The Church of St. Michael is a modern structure, erected in 1832. It is situate in the centre of the town. The south-east pinnacle, which received the electric fluid, was composed of a mass of masonry, weighing about fifteen hundred weight; the iron clamps or ties by which the work was bound together served as partial conductors. At every break in their arrangement a series of disruptive discharges of the electric fluid took place in lateral directions, driving out large masses of the stonework, spreading them over the roof of the nave and churchyard, doing considerable damage to the roofing and tombstones. The effect of the fluid when it reached the base of the pinnacle, from not meeting with a ready conducting medium, was to uplift the whole mass imparting to it at the same time a kind of circular motion to the southward, the apex of the pinnacle falling in a line with its original base; and the base having traversed about the eighth part of the circle, fell into the roof of the tower. Immediately at the base of the pinnacle there is a three-inch iron spout or tube erected to convey the water from the tower roof. This iron tube the electric fluid entered, and, finding through it an unopposed channel, passed down the tower, and finally III.At Walthamstow, at 7.30 a.m., on June 5th, 1858, the flag staff of the church was shivered, the gutters were torn up, the robing room and various parts of the exterior injured, and the gas pipes torn open. IV.Effects of lightning on a chimney stalk 240 feet high.—Facts collected by Alexander Cruickshank, 28th June, 1859: During the thunder storm at Aberdeen, between 8 and 9 a.m., 26th June, 1859, the lightning struck Messrs. Richard & Co’s chimney, 240 feet high, at Rubislaw, Bleachfield, one mile west of the city. At the height of 120 to 140 feet three patches of surface bricks were torn off. By the aid of a telescope and knowing the size of the bricks and the thickness of the mortar between them, the two largest patches of denuded bricks were 7 feet by 3 feet and 4½ feet by 3 feet—the longest measurements are vertical. These patches were visible to the naked eye at least two miles off. The parts denuded were 4½ inches thick, or the breadth of a brick when placed with its largest surface horizontal and its sides external and internal. Every fourth layer, however, of the bricks have their ends placed external and internal with respect to the axis of the chimney, and these bricks are broken across at the depth of 4½ inches, or midway between their internal and external ends, the latter being at the surface of the chimney. Thus three-fourths of the bricks of the denuded patches were torn off through the lime seam parallel to the surface of the chimney, while a fourth of the number has been broken across in the same vertical plane. Another portion of the surface bricks, 10 feet (vertical) by 3 feet, has not been entirely detached from the side of the chimney but forms a bulging of 1 foot at its greatest projection, and is visible in profile half a mile off. The lightning on striking the chimney appeared like a cricket ball, of the brightness of iron at a white heat. This instantaneously passed into a bluish flame a little darker than that of common salt when thrown on the fire. A momentary flicker and a hard crack were perceived. The lightning seems to have struck the chimney 20 feet above the uttermost denuded patch at a small abraded spot occupying a few bricks, and reddish when seen from the ground. The chimney has no lightning conductor and the damage done has not affected its stability and draught. Additional remarks, by Alexander D. Milne, chemist, of Rubislaw Works. 6th December, 1859.—Half the lower bulging part, where the force of the electric fluid seems to have become diffused or spent, fell during the gale of 3rd and 4th December. The 3rd inst. had been frosty, followed by thaw, rain, and wind from S.W. The part newly exposed is 10 feet in vertical height and 2 feet across, and the first mortar joint forms also the plane of separation, the radial bricks V.Gloucester, July 2nd, 1859.—Two clumps of objects were struck, two elm trees in the Spa walks and Rycroft Chapel—with the adjoining elm. This shows the lightning to have been forked, as they were both struck at the same time, and there was a double explosion of thunder; the extremities of the fork were 1480 feet from each other. The trees in the Spa standing close to each other were stripped from a great height, of six or seven inches width of bark, which, with the branches, was strewed to the distance of several yards. The elm at California had a large bough struck off; the lightning then ran along another branch, struck the stone edging of the roof of the chapel, scorching the end of the bough and chipping great pieces off the stone; it then ran along the metallic gutter to the end of the roof near the schoolroom, where it descended the iron spouting to the ground, bursting the spouting at the joints, where it was a quarter of an inch thick, and in one place knocked a hole in the wall ten inches deep, as if some superior conductor had attracted it inside. VI.I delayed answering your note until I could give you a correct description of the damage done to the chimney by examination from the scaffolding (which we were erecting at the time of its receipt.) The chimney is a portion of some additions made to my manure works only last November. It was struck during a fearful thunderstorm on Tuesday the 19th of July, about three o’clock in the afternoon. The electric fluid detached about one-third of the topmost stonework, which fell with great violence through the roof of the buildings below; it then displaced and passed through the joints of the remainder of the stonework to the brick shaft. This octagonal brick shaft it split and shattered in all directions on three of its sides, for a space of about twenty-five feet, completely detaching portions of Through the ventilator a portion of the electric fluid seems to have escaped from the chimney into the interior of a large warehouse, some of the main timbers of the roof of which it has split and shattered very much. A portion only of the fluid seems to have escaped in this way, as the chimney is split below the ventilator for a further space of about ten feet. Several persons were at work in the warehouse at the time, none of whom were injured in any way (although they felt benumbed.) Two strong horses standing in a cart were, however, struck down by the lightning on its escape from the warehouse. The greater portion of the chimney must come down; in fact, we are now taking it down. JOHN STERRIKER. Driffield, August 8th, 1859. P.S.—In the construction of the chimney, hoop iron was imbedded in the body of the brickwork every five or six courses, to bind it together; and this, I think, prevented the whole of the upper shaft from being thrown down, although in many places the iron has been completely fused. The total height of the chimney was 85 feet. Extract from Mr. Symons’s report on Thunderstorms in 1857–58 and 1859.[Read at the Oxford Meeting of the British Association, 1860.] Lightning Conductors.—No building provided with a conductor is recorded to have been injured during the three years; in a few cases bars or pipes of metal acted as such, so far as they extended. The first instance was at Wibsey School, where the charge, which killed one boy and injured eight others, had passed safely down an iron pendant from the roof—in fact, an iron rod of, I believe, small diameter. In the case of a house in Camden Square, the charge which overturned one end of a stack of chimneys, passed safely down the iron water-pipe at the back of the house. The flash which injured Ryecroft Chapel, Gloucester, first struck an elm-tree close to the chapel and broke off a large bough, it then darted to the roof, ran along the metallic gutter to the end of the roof, where it descended the iron spouting to the ground, bursting the spouting at the joints, where it was a quarter of an inch thick, and in one place knocked a hole in the wall ten inches deep, as if some superior conductor had attracted it inside. I presume few persons will now oppose the results obtained by the elaborate investigations of Sir W. Snow Harris, either as to the utility of conductors, or their best form and distribution. These But as no insurance nor ought else can compensate for loss of life, it becomes important to consider if any cheap and effectual substitute for a regular conductor can be found. One plan for effecting this, as far as private dwellings are concerned, is that of connecting the lead gutters of the roof with the rain water pipe, and with a rod projecting a few feet above the chimneys; it is obvious that both gutters and pipe would derive additional conducting power from the water which (at such times as the conductor is required) is usually flowing along them. I am not sufficiently acquainted with the laws of electric action to offer an opinion on this plan; as far as my own limited experience goes, I think it would be decidedly better than the entire neglect which now so largely prevails, for it would probably induce the shock to pass down the outside of the house instead of down the chimney inside, which has hitherto been its most frequent course. I much wish that those who have turned their attention to electric action would express a decided opinion on the matter. In one of the foregoing cases the iron pipe was perfectly competent and effectual in conveying the charge; and in the other the damage (limited, be it remembered, to bursting the joints) doubtless arose from the intervention of the lead between the two lengths of pipe—considering the somewhat low conducting power of the lead, such a result might almost have been anticipated. Kind of Trees Struck.—In sixteen cases the class of tree struck has been mentioned; of these one-third were elms. The next in order of this unenviable distinction are the oak, ash, and poplar; instances also occurred of the crab, the lime, and the willow being injured by lightning. It is satisfactory to find that as far as so short a series is competent, it corroborates previous opinions on the subject. I may perhaps be permitted to quote one of the earliest with which I am acquainted. In the year 1787 Mr. Hugh Maxwell wrote to the American Academy that he thought he might state from his own experience that the elm, chestnut, oak, and pine, are often; ash rarely; and beech, birch, and maple never struck. A communication with which I have been favoured by Mr. Ingram, of Belvoir Castle, bears closely on this subject, and is, I think, worthy of consideration. He says, “I filed your letter, resolving to keep a sharp look out in my rides about the neighbourhood for all the thunder-blasted trees. It is of course difficult to obtain perfectly The accounts given in the notes supplied to me by Mr. Symons are of great interest, but as the majority of the buildings struck had no lightning rods the details of the destructions do not bear immediately on the object of our Conference. There are, however, some few facts which may probably be of interest. 1.—Damp air although not a conductor for ordinary electricity (see the writings of Sir Wm. Thomson) may be a conductor for lightning:— For there are many instances of sheep and horses being killed in open fields. This may have been due to the sheep collecting together in a flock, and the air above them becoming moist from the perspiration arising from the flock. 2.—Certain coincidences of earthquake waves and atmospheric electrical storms have been observed.—The following may, perhaps, be one:— June 5th, 1858.—During thunderstorm at Pegwell Bay the water in the Bay, the tide being then about two hours past flood, suddenly receded about 200 yards, and returned to its former position within the space of about twenty minutes. 3.—Open doors allow lightning to pass through. August 12th, 1858, Bedford.—The lightning passed through five open doors in its way from a chimney, which was originally struck, to an open window, by which it went out, all the doors being on the ground floor. 4.—Difficulty of making lightning conductors to protect buildings. August 18th, 1858. Neighbourhood of Norwich—A boy riding on a pony escaped unhurt, while the pony was killed by lightning. St. Peter’s Church, Brighton.—The tower was provided with a lightning conductor, but it was only carried up one of the pinnacles, hence one of the other pinnacles of the tower was struck—the distance between the pinnacles being scarcely ten feet. New Kent Road.—While a man was sawing wood, the lightning entered by the window, struck the blade of the saw, burnt the handle, but did not injure the man. 5. A small body perfectly insulated from the ground is not safe from lightning. October 11th, 1858. Kilham, Yorkshire.—Two sea gulls, while flying, were killed by lightning. 6. Advantages of lightning conductors. During 1857, –58, –59 almost the whole of the buildings reported as damaged by lightning were unprovided with lightning conductors. Among those struck but not damaged were buildings on which metal bars or pipes acted as conductors as far as they went, proved by the lightning having burst the metallic spouting at the joints. 7. Expense of Conductors. Sir W. Snow Harris’ rule:—
Minimum cost one shilling per foot, not including cost of carriage and fixing. Sir William Thomson, at the meeting of the British Association at Aberdeen, said “If I urge on Glasgow manufacturers to put up lightning conductors they say it is cheaper to insure than to do so.” This shows the importance of economy in the construction of conductors, and consequently of the determination of the least expensive conductor, which will be safe for any special building. One of the most important points to determine, it appears to me, is whether an electric current, when the electro motive force is very high, passes along the surface or through the body of a conductor, since on the result of this must depend whether we give a lightning conductor large surface, or large sectional area—in fact, whether a tube of large diameter, but with comparatively thin walls, is better than a solid rod of much smaller diameter. In the May number for this year of the Philosophical Magazine, there appeared an interesting article, by the late Mr. Brough, “On the proper Relative Sectional Areas for Copper and Iron Lightning Rods,” in which Mr. Brough arrived at the W. E. AYRTON. |
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