Chapter XXV: Appendix: I (2)

The conductors I recommend are simply copper rods of ¼ inch diameter, attached to the highest chimney, and brought to the ground two or three feet under the surface. When buildings are longer than they are high, I always advise a conductor at each end. I generally place the conductor four or five feet above the chimney, and bring it out from the base of the building. Where a steeple or pinnacle has a vane it is only necessary to fix the conductor to the base of the spindle. Sir W. Snow Harris recommended much heavier copper conductors, but their great expense has prevented their adoption. The old conductors in men-of-war were composed of long copper links, of which nine feet went to the lb., and these were _always_ efficient _when in place_. Now of ¼ inch copper rod there are only _five feet_ to a lb., so that I give a larger margin for security.

JAMES LIDDELL.

BODMIN.

* * * * *

I observed your notice that you required information in reference to lightning and lightning conductors. A case was brought to my attention last year which occurred in Middlesborough. I enclose you particulars of the same extracted from my report, together with a tracing shewing the elevation and plan of the chimney shaft which was struck with lightning.

BALDWIN LATHAM.

7, WESTMINSTER CHAMBERS, VICTORIA STREET, S.W.

A. Wooden cover over boiler.
B. Boiler.
C. Iron disinfecting apparatus.
D. Iron flue into chimney.
E. Conductor.
* Position of fracture.

_Extract from a Letter from Mr. E. D. Latham, C.E., Borough Surveyor
of Middlesborough, dated October 11th, 1878, with reference to the
striking by lightning of the chimney in connection with the
washhouse at the Middlesborough Fever Hospital at Linthorpe_:—

“The chimney, which is a brick one, is about 50 feet high and 5 feet square at the base and stands at the north end of the washhouse, as shown on the accompanying sketch. The conductor, a ⅜th inch copper rope, is fixed on the south side of the chimney with holdfasts, no insulators, and finishes in the usual manner, about 2 feet above the top. The conductor is carried under the ground for a distance of about 9 feet from the chimney, and terminates at a depth of about 4 feet in hard, rather dry clay, the end being wrapped about three times round a common brick buried in the ground. At a distance of about 9 feet above the ground at the same side as the conductor, and only about one foot from it there is a fracture in the brickwork where the electric fluid appears to have penetrated the chimney and gone a short distance down the inside, to the flue connected with the iron disinfecting apparatus, which stands at the side of the clothes boiler, as shown on the plan. The stone work of the top of the boiler was broken and other damage done.”

_Extract from the reply of Mr. Baldwin Latham, C.E., to the above communication_:—

“It is no uncommon thing for buildings provided with what are called lightning conductors to be damaged by lightning, and the cause is due to the inadequacy of the conductor to carry the electric fluid, which will leave the conductor for a better or a larger conductor. Wire ropes are found to be one of the worst forms, the same amount of metal when applied in a solid rod or ribbon is far more efficient, as it offers less resistance than the strands of a rope. You say your conductor is perfect, but by examination of the drawings it will be seen that the lightning descended the conductor to a certain point. At this point the iron flue enters the shaft, but some distance from the conductor; the mass of metal located there was a better conductor than the rope, so that in leaving the rope for the better conductor, the electric fluid passed through the brickwork and caused the damage. If the boiler and flues did not join in metallic communication, damage would arise from the fluid passing from the flue to the boiler, and if the boiler were not in metallic communication with the earth, farther damage would arise when the fluid left the boiler for the earth. It is well known that electricity of high tension will leave small conductors for large ones, and the knowledge of this fact is made use of in protecting the telegraph system throughout the country. Many buildings and chimneys have been struck that have been fitted with so-called lightning conductors. A perfect system of protection against lightning consists in linking together all the conductors about the buildings. Such was the system introduced by Sir W. Snow Harris and adopted by the Government.”

* * * * *

_Reply of Dec. 12th, 1878, acknowledging receipt of Mr. Baldwin Latham’s Letter._

“I am directed by the Town Council to tender you their thanks for the trouble you have taken, and the valuable information you have given with reference to the lightning conductor at the Middlesborough Fever Hospital.

GEORGE BAMBRIDGE.
_Town Clerk._

CORPORATION HALL, MIDDLESBOROUGH.

* * * * *

_Subsequent action._

At the suggestion of the Engineers of the Telegraphs in the district, the earth portion of the rope has been imbedded in a mass of coke, and a quantity of old iron has been placed at the bottom of it, to counteract the influence of the boiler and disinfecting apparatus.

I beg to report an incident which occurred on board the barque “Southern Queen,” from Pensacola, while coming up Channel on the morning of the 30th of December, 1879, the Eddystone Lighthouse bearing about north, dist. 20 miles. At 6 a.m. of the above date, saw a terrific squall rising in the W.N.W. point of the horizon, with vivid Lightning in it.

We immediately reduced sails down to lower topsails and foresail, and about 7 a.m. the squall of wind and hailstones overtook us: it blew furiously for about twenty minutes, and in the height of the squall a thunderbolt broke on the ship, shattering the main royal mast-head, thence the Lightning ran down the main royal stay to the fore topmast head, and shattering that also. Thence it ran down the chain of the fore-topsail haulyard and shattered about a fathom of the chain in bits. When the bolt struck the ship it made a report like a hundred ton gun fired off. The concussion on the ship threw every man off his feet. It filled the cabin with smoke, and also the hold: the smoke had a sulphury smell; also all the compasses in the ship were so magnetized that they were flying right round.

And on arrival into the Commercial Docks we observed that a plank on each side of the ship, in the wake of the main chains, had been blown out by the Lightning. On the port side the oakum has been blown out of the seams, and the edges of the planks shattered. Since the ship has lightened up out of the water, we have discovered that the electric fluid has passed out by a copper bolt, cut the copper sheathing in the shape of a star, and turned it back.

Any further particulars I will be most happy to supply if required.

D. MORGAN, _Master_, “_Southern Queen_.”

17, LIME STREET, LONDON.

[Two of the delegates visited the ship, but with the exception of learning from the mate that he saw “a ball of fire descend from the mizen and go over the port side” they had not been able to obtain any additional particulars. They obtained some fragments of the broken chain, a much rusted iron one, weighing however about two pounds per foot.—ED.]

* * * * *

The patterns of lightning conductors obtained from Messrs. Hart, as requested, are an improvement on the first “Spratt’s Patent” purchased by the above-named firm; the original was a mixture of copper and zinc wire, which, when it was exposed to a wet and smoky atmosphere, a galvanic action took place and soon destroyed it.

About two months ago I engaged Messrs. Davis, of Derby and Newgate Street, to test a rope of the above construction that had been fixed about ten years at No. 1, Aberdeen Terrace, Blackheath, and I was present at the time, and though we had a very powerful battery we could not get a current through any part of it, as both the copper and zinc had decayed: the copper wire is not stout enough to allow for corrosion in this climate.

St. Michael’s Church, Blackheath Park, with the needle spire, as we call it—built just fifty years ago—had a ½ inch iron rod; and as it now runs through the new vestry just built I have advised the churchwardens to have it tested, and they are going to have it done in the course of a week or so.

St. Alphege Church, Greenwich, has a ribbon of copper about 1½ inches wide by ¼ inch thick, and that has been up many years, and is as sound as when it was fixed, for I examined it about two months ago.

I have advised the owner of No. 1 Aberdeen Terrace, to have a ribbon of copper, as I am certain that wire ropes are not to be depended on in this climate.

Hoping these few remarks will not be deemed out of place,

CHARLES J. HERYET.

95, BLACKHEATH HILL, GREENWICH, S.E.

* * * * *

I have the honor to forward notes of an accident from lightning, which I lately witnessed, having been informed that your Committee desires such information.

The very rough sketch which I attach is, I believe, accurate; but I was only allowed to look in at the door while a strong light was held within, and to view the outside of the building. A native draughtsman belonging to the office, however, was allowed to make some measurements, which he communicated to me.

It seemed to me that the case was worthy of record, because the building was so little injured.

JOHN ASTED, Lieut.-Col. R.E.

MASULIPATAM,
MADRAS PRESIDENCY,
_17th May, 1878_.

_May 8th, 1878._—Camped at Pedda Kondur, a village on the west bank of the Kistna river, about 10 miles below Bezoarah anicut. All the morning there was a southerly wind blowing unsteadily; by noon it fell calm, and was very hot, clouds gathering in the east. Soon after midday thunder was heard to the east, and a storm was evidently approaching. About 3 p.m. wind began to blow from the east, and soon rose to a gale, bringing thick clouds of dust, and the thunder sounded very near. It rained rather heavily, which laid the dust, and black clouds could then be seen over-head, and nearly all round: the thunder, which was very loud, sometimes sounding quite over-head. By half-past four the rain had slackened, but thunder was almost incessant, and very loud. Just at this time a stream of lightning descended within 80 yards of the tent, and was accompanied by a tremendous explosion. The lightning struck a small pagoda near the village, and some of the natives said that they observed smoke rise from the summit when the lightning descended.

The accompanying rough sketch will show what the building is like. The main part of it is a square pyramid, each side of the square, outside measurement, being about 18 feet; height of apex above ground, 32 feet. Built on to one side of the pyramid is an entrance chamber, with flat roof, about 10 feet square, and the same in height. The apex of the pyramid is surmounted by a metal (probably copper) finial, about 1 foot in height; the ordinary attachment of such a finial to masonry is by means of a small stake built into the masonry, on which the finial—which is cast hollow—is fixed, and round which it is plastered with mortar.

The interior of the pyramid forms one room, about 10 feet square, with a domed ceiling, the thickness of the dome at crown being 2½ feet. In the centre of this room is placed the idol, in this case a lingam, or cylindrical stone pillar, 1 foot 4 inches high, and about 9 inches in diameter, which stands on a square hollow stone tray (not cut out of one stone, but fitted in two or more pieces) in which the offerings of ghee, &c. are placed. This tray has a small spout on each face to carry off the liquid ghee and water with which the priests’ ablutions are made. The tray is raised on masonry, so that the height of the top of the lingam is 3 feet 4 inches from the floor. The floor of the room is 1 foot above the surrounding ground; there is only one doorway leading from the porch or entrance room above mentioned; and the sacred edifice is closed by a substantial wooden door, with iron hinges and lock, on the outer face of the entrance chamber. The whole building is of brick in mortar, unplastered, and presents the appearance of being weather worn.

The pagoda is at a distance of about 20 yards from some low native houses, and stands in an open space, on two sides of which is the native village; round the houses are some trees, mostly of small size, but within 50 yards of the pagoda are two separate trees, which certainly exceed it in height. The village is situated on the margin of the Kistna river, and the surface of water in wells is at least 10 feet below the surface of the ground.

The lightning struck the metal finial on the top of the pagoda, and passed vertically through the dome, travelled along the east side of the lingam without leaving any mark, and bored a small round hole in the stone tray beneath it, passing into the ground below without disturbing the idol or its foundation. The hole in the tray was not quite large enough to admit the point of a little finger, and it was situated on a joint of the stone, a place where moisture would probably linger. The finial appeared undisturbed, but the masonry immediately round its base was shattered, and a shower of pieces of brick and mortar was sent from the top of the pyramid and scattered over the ground on the east side to a distance of about 20 feet from the base. The masonry of the apex of the pyramid was cracked in three places, and a small hole was bored in it, on the east side of the finial, apparently about the same size as that in the stone tray; but otherwise the masonry of the building appeared totally uninjured—not a crack could be found anywhere.

The soil at this place is a clayey loam, rather lighter than the ordinary delta alluvial soil.

When the building was struck a sulphurous smell was noticed.

JOHN ASTED, Lieut.-Col. R.E.

MASULIPATAM,
_17th May, 1878_.

* * * * *

IRISH LIGHTS OFFICE, DUBLIN,
_13th March, 1880_.

SIR,

Adverting to your letter of the 13th ultimo, I have now the honour
to forward herewith for the information of the Lightning Rod
Conference copies of two Reports relating to the lighthouse at
Berehaven being struck by lightning, in 1877, which, no doubt, is
the Station alluded to by Professor Tyndall in his conversation with
Mr. Inglis, of the Trinity House.

I am, Sir,
Your obedient Servant,
W. LEES, _Secretary_.

* * * * *

IRISH LIGHTS OFFICE, DUBLIN,
_February, 1877_.

SIR,

I most respectfully beg leave to state that, in accordance with your
instructions I proceeded to Berehaven Lighthouse, and on my arrival
at that station I made a very careful examination and found that the
lightning was conveyed into the lantern by the iron stay bars that
were connected to the lightning conductor at a collar about 5 feet
over the gutter on the outside of the dome for the purpose of
securing it, and bolted to the dome of lantern by iron bolts. After
bursting off the several coats of paint at the heads of the bolts,
it put out the lights, breaking the glasses, and knocking down both
light keepers insensible; it having twisted off the lead voice-tube
where it was secured to the side of the lightroom by a holdfast,
bursting out the stone sheeting between the iron pillars supporting
the marble top; it then passed through the voice tube to the
principal keeper’s bedroom, where it burst out the studding and lath
and plaster, and tearing away the voice-tube, the foot-board of the
bed, and destroying the pictures that were hanging on the walls. It
would appear that the current was interrupted in its course by the
sudden bend of the voice-tube; for, after having dealt destruction
in this apartment it was attracted by the iron holdfasts and spikes
that secured the voice-tube and studding to the walls, and passed
out through the external walls of dwelling to the out offices, where
it passed along the eave gutters to the end of them; it then
followed one of the iron holdfasts, and entered the wall, destroying
it, and bursting out the cut-stone kneeler and barge course, it then
passed down through the roof of the low buildings, destroying the
slating, passing through the walls of the pantry, &c., tearing up
portions of the 3 inch Yorkshire flagging of the floor and yard,
dealing destruction to the shelving, doors, door frames, brickwork,
glass, &c., and bursting up the seat of principal keeper’s w.c., it
passed along the sewer to the assistant keeper’s w.c., breaking up
the flags and seat and then passed out through the roof. Another
current was attracted by the eave gutters at the east angle of the
dwelling near the tower, and passed along them to the north east
angle, splitting them through the centre. At this point its course
was changed to the west, and passed into the assistant keeper’s yard
and down the rain water pipe to the water tank, splintering it and
the slating and brick wall, &c.; it also appears that the lightning
struck the south-east side of the tower and entered it in several
places at the base and near the lightning conductor, and apparently
glanced off it where it was secured by holdfasts to the tower,
rooting up the solid rock, but giving no indication that it had been
conveyed to earth by the conductor as intended: the lightning also
entered the assistant keeper’s kitchen through the chimney, knocking
down a portion of the brickwork, &c.

I may remark that the lightning conductor is formed by a copper rod,
which stands about 10 feet over the gutter on the outside of the
lantern, and is secured by three iron stays to the dome, as before
described, and passes down through the centre of the gutter to the
under side, where it is connected to a ½-inch copper-wire rope,
which continues down the outside of the lantern close to the glass
to the floor of the balcony, passing through the stone floor by
means of a hole, jumped through it, then continues down the face of
the tower closely pressed to it by the iron holdfasts and copper
bands, which secure it until it reaches the rock at the base of the
tower, where it terminates in a small hole 3 inches by 3 inches,
jumped out of the rock about 6 inches under the surface.

After having made a careful survey of the damage done, I deemed it
advisable, and at the solicitation of the principal keeper, who
seems to have been greatly shaken and nervous, to have the iron
stay-bars disconnected from the dome of the lantern and the
bolt-holes plugged up with timber, fearing a recurrence of the
accident, as the weather was very stormy, and should lightning come
on no person on the rock would enter the lantern. I also considered
it prudent to have the loose gutters and cut-stone, also a part of
the gable of the out offices, taken down, as it was in danger of
falling into the narrow yard, which might cause a sad accident.

Having provided workmen and materials and scaffolding for doing this
work I again landed on the rock on Saturday last, with great
difficulty, having been detained a day by the storm, and pointed out
the temporary repairs that were necessary to be done for the
protection of the people on the rock.

The probable cost of repairing the damage done the buildings,
independent of the lightning conductor, and which require to be done
without delay, will be £120. Hoping the action I have taken in this
matter will meet with your kind approval, I have the honour to be

Your most obedient Servant,

(Signed) A. J. BERGIM.

[The other report is to the same effect as the above, and is therefore omitted.—Ed.]

* * * * *

ACCIDENT BY LIGHTNING _at Upwood Gorse, Caterham, the residence of_ J. TOMES, Esq., F.R.S. _28 May, 1879_.

As I happened to be visiting Mr. Tomes, in the autumn of 1879, I took the opportunity of obtaining all the particulars I could with reference to the accident which occurred on the night of the 28th May, 1879, when his house was struck by lightning.

The house, a sketch plan and elevation of which are annexed, stands upon a hill upwards of 700 feet above sea level, and is somewhat higher than any other object in the vicinity. It is covered by a steep tiled roof, that of the principal portion of the house being somewhat higher than the rest, and upon the ridge of this roof stand two brick chimney stacks of equal height. Upon the eastern stack, at its southern end, was fixed a lightning conductor (shown by the line, A. B. C., on the south elevation), the upper part consisting of a point and a length of copper tube ½ an inch external and ⅜ inch internal diameter, which was screwed into a collar connected to a woven band of one zinc and thirteen copper wires carried through glass insulating rings along the slope of the roof, over the rain-water gutters and down the side of the house into the ground, going only 12 inches into dry chalk.

The electric fluid struck the lightning conductor, hurled the rod down and shattered the chimney pots and some of the brickwork. The rod was broken at the point marked A on the south elevation, where the sectional area of the copper rod was reduced by the screw being cut into it for the collar, which connected the rod with the woven band. This junction and a portion of the band are forwarded for inspection, from which it will be seen there are no rough broken surfaces, but that the thread of the screw was partly melted. The copper wires composing the band were bright and nodulated here and there throughout their length, showing that it had been heated up to a sweating temperature. The zinc wire was not continuous, having been wasted by oxidization. It showed no indication of having been hot.

UPWOOD GORSE, CATERHAM. Scale—1 inch = 32 feet.
]

Having broken the conductor, the discharge appears to have divided at the ridge of the roof, a portion passing down the southern and a portion down the northern slope of the roof. That portion which passed down the southern slope apparently followed the course of the conductor band as far as the iron rain-water gutter, which it cracked, and perforated two holes, about half an inch diameter, in two panes of glass at B. Here the current apparently again divided, as shown by the dotted line from D to E on the south elevation, some passing westwards and some eastwards along the rain-water gutter round the eaves of the house, as traced by the broken joints of the gutter. Westwards these joints (which were made of red lead) were only broken from B to D, but eastwards they were broken from B to E, and right round the eastern side of the house to F, and along the northern side as far as G.

What seemed to be the greater portion of the discharge, however, passed down the northern slope of the roof and along the course shown by the dotted lines on the Plan and north elevation. The lightning first followed the lead flashing H of the chimney stack, next broke some tiles at I, and then without disturbing any of the rest of the tiling, leapt across the roof, a distance of some 15 feet, to two galvanised iron water cisterns in the roof at K, perforating a hole through the 9–inch brick wall of the house in its course.

This hole, which was circular, was large enough to admit one’s finger easily and was blackened on its interior; when first examined, eight or ten minutes after the occurrence, it was still quite hot. One edge of the lead flashing outside the wall was fused at G, close to the rain-water gutter, from which it would seem that the current again divided at the wall of the house. There are two galvanised iron cisterns at K, connected by a pipe underneath (see adjoining sketch plan), and the discharge appears to have passed from one cistern to the other and then along the 1½ inch iron barrel rising main, from pumps, to the point L^1 in the back kitchen, where the iron pipe separated into two branches leading to the two pumps L^2 and M.

Probably a portion of the discharge passed down the iron suction pipe from the pump L^2 into the rain-water tank P, but however this may have been, a considerable portion passed from point L^1 along the 1½ inch iron pipe LM to the pump M in the scullery, and thence along a ¾ inch iron pipe to a water tap fixed over the iron sink N, but not in metallic connection with it. Here the lightning broke the slate at the back of the sink and sent it showering across the scullery, breaking the things on the opposite side of the room. The iron sink was set on brick piers and connected, by means of a 1½ inch iron pipe, with the self-acting syphon “Flush Tank” O in the yard. This “Flush Tank” consisted of a cylindrical cast-iron tank about 26 inches in diameter and 26 inches deep, buried two-thirds in the ground, so that it formed a fair earth connection.

There is an account of the accident in a letter by Mr. Charles S. Tomes in _Nature_, of 12 June, 1879 (which has been made use of in the present description), and there is also a letter about the accident by Mr. Newall on the next page of _Nature_ to Mr. Tomes’ letter. The description in this latter letter is, however, erroneous in several particulars, especially where it speaks of the lightning passing round the iron gutters to the iron water cisterns.

ROGERS FIELD,
_B.A. Lond., M. Inst. C. E., F.M.S._

CANNON ROW, WESTMINSTER.

[NOTE.—Mr. Tomes has most kindly sent the whole of the upper parts of the conductor; and as the accident appears a very instructive one we give full details, together with engravings of the more important portions of the conductor.—ED.]

This conductor was of the pattern known as Spratt’s patent. The upper terminal was what the vendors call a “reproducing point,” which they say is “formed of two or more metals: the inner or core being steel, and the outer of silver alloy, tipped with platinum;” the idea of the inventor is said to have been that “should the outer coating become fused by an extraordinary charge of electricity, the core will remain intact to receive any further discharge.” In the present case the top is broken and the iron centre is rusted and bent, but there is no indication on the remaining portion of heat or fusion.

This point A was well screwed into a stout copper collar B.

D
]

F
]

Into the same collar was screwed the upper end of a copper tube C, 5 ft. 1 in. long, external diameter, 0·5 in., and internal diameter about 0·36 in., giving a thickness of only 0·07 in., or but little more than a sixteenth of an inch. The mass of copper was therefore about equal to a tape 1½ × 1/16, or ¾ × ⅛, or to a rod one-third of an inch in diameter—the area being as nearly as possible 0·09 in. The tube weighs 29½ ounces, which corroborates the above measurements and shows that it weighs rather less than 6 ounces per foot. This part of the conductor was evidently greatly heated, as there are distinct marks of sweating in several places. The lower part of this tube was screwed into the collar D (which is drawn of its actual size in the annexed sketch) in order to make connection with the short length of copper tube F, a portion of which is also engraved, of its actual size. It was at E that the rupture occurred. The charge passed the point A, then the top collar B, and although it greatly heated the 5 ft. copper tube C, still no damage was done, and so it passed into the second collar. Here, however, there seem to have been two faults: the short copper tube F, was very slight, weighing but little over 3½ ozs. to the foot, and this, which represents but a very slight conductor, was greatly lessened by a deeply-cut thread to the upper end, whereby the area was reduced to less than 1/20th of an inch. As this was not screwed home, the total sectional area at E immediately below the collar was reduced to the above small amount, rupture and fusion occurred, and much of the charge left the conductor. This short length of tube was, however, raised to a sweating temperature in two places.

The conductor consisted of 14 wires made into a flat plait, the wires seem to have been of the following dimensions:—

Each of No. Total area.
12 copper wires, 15 B.W.G., dia. of each ·072 in.: 0·048 in.
1 copper wire, 18 B.W.G., dia. of each ·049 in.: 0·001 in.
1 zinc wire, of each ·049 in.: 0·001 in.

Thus the total sectional area of the plait G would be about 0·050 in., or rather more than that of the short copper tube into the lower end of which it was roughly thrust and riveted—but the joint was bad, there was no solder at all, and the metallic contact was very imperfect.

As to the state of this plait (which was less than an inch wide, and less than ⅒ in. thick), and as to the ridiculously imperfect earth terminal, details are given in Mr. Field’s letter.

It may be well to recapitulate the dimensions:—

┌─────────────┬─────────────┬─────────────┬─────────────┬─────────────┐ │DESCRIPTION. │ LENGTH. │ DIMENSIONS. │ SECTIONAL │HEAT EFFECTS.│ │ │ │ │ AREA. │ │ ├─────────────┼─────────────┼─────────────┼─────────────┼─────────────┤ │“Reproducing │ 9 in. │0·45 × 0·45 │ 0·20 │None visible.│ │ point” │ │ in. │ │ │ │Collar │ 1¼ in. │0·75 in. │ 0·24 │None visible.│ │ │ │ diam. │ │ │ ├─────────────┼─────────────┼─────────────┼─────────────┼─────────────┤ │ │ │External 0·5 │ │ │ │ │ │ in. dia. │ │{Sweated in │ │Copper tube │ 5 ft. 1 in. │ Internal │ 0·09 │ places. │ │ │ │ 0·36 in. │ │ │ │ │ │ dia. } │ │ │ ├─────────────┼─────────────┼─────────────┼─────────────┼─────────────┤ │ │ │External 0·75│ │ │ │ │ │ in. dia. │ │ │ │Collar │ 1⅛ in. │ Internal │ 0·24 │None visible.│ │ │ │ 0·50 in. │ │ │ │ │ │ dia. │ │ │ ├─────────────┼─────────────┼─────────────┼─────────────┼─────────────┤ │ │ │External 0·50│ │ │ │ │ │ in. dia. │ │{Sweated in │ │Short tube │ 7 in. │ Internal │ 0·09 │ places. │ │ │ │ 0·375 in. │ │ │ │ │ │ dia. │ │ │ ├─────────────┼─────────────┼─────────────┼─────────────┼─────────────┤ │ │ │External │ │ │ │Short tube │ │ 0·438 in. │ │ │ │ where │ ¾ in. │ dia. │ 0·04 │Fused. │ │ threaded │ │ Internal │ │ │ │ │ │ 0·375 in. │ │ │ │ │ │ dia. │ │ │ ├─────────────┼─────────────┼─────────────┼─────────────┼─────────────┤ │Plait │ 53 ft. │? 0·7 × 0·072│ 0·05 │Sweated in │ │ │ │ in. │ │ places. │ └─────────────┴─────────────┴─────────────┴─────────────┴─────────────┘

G. J. S.

* * * * *

We herewith hand you our circular, setting forth our ideas as to lightning conductors. We claim that if one or more sharp edges or points is so essential on the most elevated part or parts of a conductor, why not establish this principle the entire length of the conductor? or why not leave these most elevated part or parts blunt, or erect a small gilt ball?

DAVID MUNSON & Co.

INDIANAPOLIS, INDIANA, U.S.A.

[The engravings are not drawn to scale, but are here reproduced; the
shaded parts are galvanized iron, the lighter parts copper.—ED.]

* * * * *

I think that it would be very valuable if the Conference considered how far iron ventilating pipes to drains will safely act as lightning conductors. These pipes generally consist of iron jointed with red lead or putty. Will not these joints interfere? Very often also a portion of the pipe is wholly of lead. So many of these pipes are now carried up to a very high level that the question is important.

ROGERS FIELD, M.Inst.C.E.

CANNON ROW, S.W.

* * * * *

Our opinion is that the drain to our Powder Magazine at Bruntcliffe (see ante page 74) had no water in it at the time of the occurrence.

JOHN HAIGH & SONS.

VICTORIA COLLIERIES,
GILDERSOME.

* * * * *

We have the pleasure to send you a plated model of our new Conductor Coupling, and hope you will be pleased with it.

When screwed up, the contact between the rod and the copper tape is perfect. It is, of course, a very simple thing, but it overcomes the difficulty of soldering, which is always more or less uncertain, and rivetting up aloft is apt to be scamped.

And as to soldered connections, apart from the uncertainty of permanent contact, it is very important to keep the soldering iron away from roofs, it often damages the lead, and (as at Canterbury) the fire-pot is a source of great danger to buildings.

FIG. 1.
]

FIG. 2.
]

FIG. 3.
]

A is the copper tape conductor. B is a screw plug, having two slots, _a a_ (see fig. 3), and an intervening division _b_, all cast in one piece. The tape or rope A is passed through one of the slots _a_, and bent over the division piece _b_, the bent portion A1 is then returned through the other slot. A screw socket forming the coupling C, bearing a collar to rest in a ring bolt built into the structure to be protected, is then screwed on to the plug B, and into this socket the rod or tube D is screwed, it being suitably tapped for its reception, until the lower end of the rod or tube is in firm contact with the tape or rope. These latter are then firmly held together, and cannot by any possibility come apart.

NOTE.—In fig. 2 the rod and tape are not shown in actual contact, the drawing being intended to exhibit the separate parts.

R. C. CUTTING & Co.

147, QUEEN VICTORIA STREET.

* * * * *

I have the pleasure of furnishing details of the recent damage to Christ Church, at Carmarthen. The circumstances are these:

At the Eastern end of the church stands an ordinary square tower, covered with a sloping slated roof; this roof is capped by an ornamental open ironwork ridging, terminating at each end in a light open iron pinnacle, and having in the centre another pinnacle similar to those at the extremities. A is a view of this ironwork from the east end of the church.

The conductor consisted of seven copper ropes stranded together, each rope consisting of seven strands of No. 18 wire, the whole having a diameter of about ½ an inch. It was fixed to the building by ordinary copper staples; it ran up, and was attached to the southern portion of the ornamental railing, and it terminated in a single point. There was no special connection between the conductor and the iron guttering of the church.

I could not ascertain in what manner the earth was made, but it was an imperfect one, giving a resistance of 115 ohms, and this resistance would have been greater but for an accidental circumstance mentioned further on.

The lightning struck the central iron pinnacle of the ornamental ridge and broke it off. In falling to the ground it was shattered into about twenty pieces; but on the upper extremity, which was a solid cast-iron spike, about ¾ inch square, there were marks of fusion across the whole of the top to the depth of ⅛th of an inch.

I could not observe other marks of fusion at the point where the pinnacle was broken off, but the lightning made its way to the conductor, and on reaching the ground, at a distance of 4 feet from the point where it entered, it burst out with explosive violence, blowing a circular hole in the ground 2 feet in diameter and 8 inches deep (marked B in plan). The earth from this hole was blown into the air, and fell in a fine shower on objects standing 3 or 4 feet high and 14 or 15 feet from the hole.

CHRIST CHURCH, CARMARTHEN.
]

A second flash struck the iron guttering at the south-western extremity of the church (C), broke off a 2 feet length, and ran down the waterspouts (D D). Opposite one of these a second hole, 9 inches deep and a foot in diameter, was blown out of the ground, some 3 feet from the base of the spout.

On examining more closely the surroundings of the lightning conductor, I observed that the church gas-pipe, an iron one, about 1¼ inches in diameter, passed through the wall of the building about 6 feet from the conductor, and was carried in a direction corresponding with the hole caused by the explosion (see plan). I immediately concluded that this explosion was due to the current breaking across from the conductor to the gas-pipe, and on opening up the hole I found this to be the fact. The conductor crossed the gas-pipe at nearly a right angle, being about a foot above it. The under portion of the conductor bore evident marks of fusion, and, more interesting still, the gas-pipe was slightly coated with a very thin deposit of copper, so thin that it perished in my attempt to remove it; but still there was an undoubted coating at one spot. But for the proximity of the conductor to the gas-pipe, the earth resistance of the former would doubtless have been greater than it was, and the damage would probably have been increased.

I was sorry that no means existed for examining the ornamental ridge, but doubtless the metallic contact between the sections was very imperfect, and to this cause was due the rupture of the pinnacle.

The fact, too, that the protector did not prevent the south-western portion of the building being struck bears on the question of the area made safe by a protector.

The tower stood 89 feet above the ground, the top of the iron pinnacle 99 feet, and the protector extended 1 foot 6 inches above the latter, thus reaching a total height of 100 feet 6 inches. The total length of the church was 123 feet.

The point C where the gutter was struck was 84 feet in a direct line from the conductor, and stood 24 feet above the ground. This gives a vertical height of the conductor of 76 feet 6 inches above the point struck, the distance of the latter being a radius 8 feet greater than the height of the former.

J. GAVEY.

CARDIFF,
_January 10th, 1880_.

ACCIDENT AT BOOTHAM BAR, YORK, COMPILED FROM NOTES AND MEASUREMENTS
TAKEN BY J. EDMUND CLARK.

The discharge occurred about 3 a.m., 22nd June, 1876. The principal injury occurred to the bracket lamp at A. This lamp, which was an ordinary street one, was supported by an iron bracket 2 ft. 6 in. long, and 11 ft. 6 in. above the pavement. The gas was conveyed to it by 11 ft. 6 in. of vertical iron gas barrel, and thence to the burner by about 3 ft. of ordinary ½ in. composition pipe. The glass of the lamp was not broken, but about 18 inches of the composition piping was twisted and split open as with a sharp knife, and the other 18 inches was melted; the gas was ignited and burning from the top of the iron barrel, thus producing a large flame which ignited the house to which it was fixed. That part of the lead pipe which was inside the lamp was uninjured, whence it would appear that the point struck was at or near to the top of the iron gas barrel; and this is supported by the fact that the lead over the shop window and close to the bracket was turned up off the wood-work.

The lamp, as will be seen by the plan, is attached to the corner of a house, the eaves of which were 20 ft. above the lamp, while the ridge, with a little lead flashing, was 24 ft., and the chimney pots were 31 ft. above the lamp, and not 15 ft. distant horizontally. This house was slated and had wood gutters, and an iron rain-water pipe, but the latter was 33 ft. horizontally from the point struck. The wooden gutters were very old and rotten, and one of them was very slightly shifted; it is not certain that this was done by the lightning, and there was no other indication of its presence.

C is a lamp bracket extending 4 ft. from the wall of the house, and at D are two old iron brackets.

At the distance of only 8 ft. from the lamp in the opposite direction (N.W. of the lamp) rises Bootham Bar, a massive stone structure, of which the four turrets rise to 44 ft. 3 in. above the pavement, and therefore 33 ft. above the lamp. The whole roof, about 750 square feet, is covered with thick sheet lead, and the building also contains the old portcullis B heavily shod with iron.

The noteworthy feature of the case appears to be, that the only injury is found at a spot surrounded by objects close to it, and greatly exceeding it in height; in fact, that the lightning dipped into a sort of cavity, instead of striking at the higher objects.

It is evident that in this case, although the composition pipe was melted, the _iron_ one afforded ample conduction, and the city gas mains a perfectly safe earth terminal.

SOUTH-EAST VIEW OF BOOTHAM BAR.
]

ACCIDENT AT BOOTHAM BAR, YORK.

VIEW OF HOUSE AND SECTION OF BAR.
]

GROUND PLAN OF HOUSES AND OF BAR.
]

REFERENCES.

A Gas bracket struck.
B Iron sheathed portcullis.
C Old gas bracket.
D Old Iron brackets.