several places to be connected to it; but, on the other hand, they
must be kept, electrically, as distant from all other parts of the
building as possible, especially from the metallic parts of it.
NOTE 2.—If ground water is found at a considerable depth, under a
dry layer of sand, a second plate, besides the general earth plate,
ought to be placed just beneath the surface of the earth, the latter
being made temporarily conductive by rain.
NOTE 3.—As to powder magazines, which of course must be constructed
of bricks or wood, the lightning conductors must not, without
inevitable necessity, be placed on the building itself, but,
retaining the above-mentioned dispositions in the main points (the
top conductor excepted), they ought to be placed on masts, about ten
feet from the magazine.
Figure 2 shows a system of lightning conductor for a powder
magazine, a hundred feet in length, with gable roof.
[Illustration:
End and Side elevation.
]
[Illustration:
Plan.
]
B. _Construction._
_The point_ ought to consist of a solid copper cylinder, ¾ inch
diameter, 6 inches high, conically pointed, the top angle being
about 30 degrees, and with gilt top. At the lower end a nut is
applied, by which the point is screwed and afterwards soldered to
the end of the rod. Most conveniently the rod is formed of round
iron, which, like the rest of the conductor above earth, if
constructed of iron, is painted over or galvanized. Under earth only
galvanized iron is suitable. The upper diameter of the rod is ¾
inch; 12 feet farther down, 1½ inch. The length is properly varying
between 10 and 16 feet. It is to be preferred to use a greater
number of low rods rather than fewer high ones. _The conductor_, as
also the top and earth conductors, may consist of an iron bar, of ⅓
square inch section, consequently 9/16 inch in the square side, or ⅝
inch in diameter. Only for very great lengths will it be necessary,
on account of the increased resistance of the conductor, to use
thicker bars. In place of iron, copper may be used, the section of
which need only to be ⅒ square inch. The conductors must be of as
short a length, and with as few bends as possible; and the latter
must be rounded at their angle points. They ought not to be bolted
or spiked to the building, but, in view of changes of form
occasioned by temperature or other reasons, they must rest in hooks,
or be kept up by cramps that are fastened in wood or brick, far from
the metallic parts of the building. It is of the utmost necessity
that the conductor be continuous in its whole extent, from the point
to the earth plate. Links of chains or cables are to be rejected.
For this reason the number of joints must be limited, and a constant
contact of the respective ends, extending over one or two square
inches, procured by bolts or rivets and soldering. The metal should
be filed on the contact sides, so as to clear it from oxide, this
being an insulator, and the soldering made with tin. _The earth
plate_ may consist of galvanized iron or copper. It ought to have at
least a surface of 10 square feet in water, or 5 square feet area,
if to serve one conductor; for each conductor in addition 50 per
cent. must be added to the area. To diminish the circumference of
the well, the plate may be given a cruciform transverse section; if
then, for instance, the plate reaches 2½ feet down into the water,
the wings need only have the length of 6 inches. _The well_ is
constructed in the usual manner by digging or boring. In order to
preserve the conductor from breaking, as the plate might press
deeper into the ground, a beam is placed across the well’s upper
part on which the horizontal part of the conductor rests.
_Inspection_ of the lightning conductor must be effected once a
year, and, besides, when circumstances demand it, for instance,
after a stroke of lightning. The inspection must especially have the
purpose:
1. To examine whether the metallic continuity remains perfect; to
verify this a galvanometer is inserted, and a galvanic current led
through the conductor; and
2. To examine whether the conductivity to ground water is in order.
The earth plate being placed in a well, instead of being buried in
the ground, will greatly facilitate this examination.
Dec. 8th, Rome.—Sig. D’Amico sent a copy of a letter received from
Professor Tacchini, Director of the Central Meteorological Office, in
answer to the communication made to him of the circular dated October
31st. The following translation has been kindly made by Professor T.
Hayter Lewis:—
METEOROLOGICAL CENTRAL OFFICE, ROME.
_November 27th, 1879._
LIGHTNING RODS IN USE IN ITALY.
Although I have not sufficient material for giving a complete answer
to the request made in your letter, as noted in the margin, yet I
think that the accompanying notice as to the system in use in Rome
for fixing lightning rods may be useful to the Director General.
1. The conductor of the lightning rod is constructed of iron, 17
millimetres (c. ⅔rds. inch) diameter. The upper terminal or receiver
is 4·5 metres (14 feet 9 inches) high, with a copper point 0·50 (c.
1 foot 8 inches), gilt from 0·25 (c. 10 inches), fixed on a pilaster
of masonry 2 metres (c. 6 feet 6 inches) high, and 60 centimetres
(c. 2 feet) wide. Each terminal is intended to protect a horizontal
superficies of radius double its height.
2. In order to obtain a conductor as long as required, pieces of 5½
metres (c. 18 feet) are united by a holdfast of brass. The fastening
of the conductor to the walls and roofs is made by little pieces of
marble of the annexed form, connected with the fabric.
[Illustration: Attachment and Earth Terminal used in Italy]
A—Wall or roof.
B—Little piece of marble.
C—Hole through which the conductor passes.
3. It is the custom to connect the conductor with masses of iron,
and other metals in the building to be protected, avoiding the water
pipes. (Referring probably to Terra Cotta pipes. T. H. Lewis.)
4. In addition to the upper terminal and chief receiver, it is usual
to fix secondary points according to the form of the building.
5. The discharger or lower terminal (in contact with the earth) is
made of copper rod, 12 millimetres (c. ½ inch) square, at least 6
metres (c. 20 feet) long, in 3 strips with points of copper arranged
in the manner shown—
[Illustration: Attachment and Earth Terminal used in Italy]
D—Conductor.
E—Lower terminal or discharger with points of copper.
6. The discharger is introduced into a ditch or well excavated in
moist ground, vertically or horizontally, according to the
circumstances of the locality. The diameter of the well should be
0·80 metres (c. 2 feet 8 inches), filled with carbon, and covered
with earth.
7. In an ordinary building we employ a discharger to each 3 points.
8. In this manner were made all the lightning rods of P. Secchi, by
Signor Lerigi Morea, maker of them in Rome.
9. In some cases P. Secchi has made use, for the conductor, of the
thicker wire used for the Telegraph.
10. We may observe that, in other Italian cities, the same rules are
adopted for the construction of lightning rods, as I myself have
verified. Only, in some localities, in place of putting points of
copper to the lower terminal the latter is terminated by a copper
band.
P. TACCHINI,
_The Director_.
Dec. 9th, New York.—Mr. G. G. Ward acknowledges receipt, states that the
only papers of any value upon lightning conductors, published in America
and known to him are:—(A) a paper by Prof. Henry; (B) a treatise by
Prof. Phin; (C) a pamphlet by David Brooks; (D) a practical treatise by
H. Spang. The writer furnished copies of Nos. B and D, and all four will
be found noticed in the Abstracts of Printed Documents. See pages (99)
(102) (117) and (112.)
Dec. 12th, Calcutta.—Mr. F. G. Teale acknowledging receipt of circular
and forwarding copies of two papers accepted as authoritative in India,
viz:—(1) R. S. Brough on Protection of Buildings from Lightning, and (2)
W. P. Johnston on the Lightning Conductors at Dum Dum. (See Abstracts,
pages (117) and (132).)
Dec. 13th, Washington, U.S.A.—Lieut. Kilbourne acknowledges receipt on
behalf of Gen. Myers, enclosing copy of paper by Prof. Henry, and
stating that the works of Spang and Phin are considered authoritative.
APPENDIX I.
GENERAL CORRESPONDENCE.
TRINITY HOUSE, LONDON, E.C.,
_6th February, 1880_.
SIR,
I am directed by the board to transmit to you herewith, for the
information of the Lightning Rod Conference, copies of reports made
by Professor Faraday to this Corporation, one respecting a
remarkable stroke of lightning which occurred at the Eddystone
Lighthouse in January, 1853, and the other upon a similar accident
experienced at the Nash Lights in August, 1852.
The case to which Admiral Sullivan directed the attention of the
Conference, as stated in your letter of the 30th October last, was
probably one of these two.
Should you desire any further details in connection with this
subject, the Corporation desire me to assure you of the pleasure
with which they will afford any information at their command.
I am, Sir,
Your obedient servant,
ROBIN ALLEN.
G. J. SYMONS, Esq.
[We have been favoured with copies of three separate reports by
Professor Faraday, and think that it is better to give them in
chronological order. There is only one other point in the correspondence
from the Trinity House which it seems necessary to mention, viz., that
the sections of the copper rods now used are as under.—ED.]
[Illustration:
MAIN CONDUCTOR.
1½ in.
]
[Illustration:
CONNECTING BRANCHES.
1¼ in.
]
REPORT ON THE LIGHTNING RODS OF LIGHTHOUSES, 1843.
DUNGENESS.—Dungeness Lighthouse stands about 14 feet above the sea and
measures 97 feet to the top of the lantern. The tower is of brick with
wood floors; the roof and frame of the lantern are of metal seated upon
a stone pedestal, to which it is secured. There is no conductor to the
building. The weathercock is fitted with a glass repeller, and a rod
similarly fitted is attached to the two copper flues which rise by the
side of the lantern.
EDDYSTONE.—The height of the top of the lantern of the Eddystone above
the sea is about 95 feet. The roof and framing of the lantern are of
metal, secured through a stone plinth to the gallery of the tower by
metal fastenings. A conductor of copper rod, ¾ inch diameter, is
attached to the outside of the building; the rod rises 3 feet above the
top of the lantern and terminates in the sea at low water; it is fixed
to the tower and lantern by metal stays and fastenings and is isolated
by glass ferules. To give stability to the building eight wrought iron
ties are fixed in the interior of the house, extending downwards from
the underside of the lantern floor through the next two stories,
terminating by inserting the ends into the stone floor, the upper ends
are riveted into an iron ring round the manhole in the ceiling and
further secured by iron bolts passing through the stonework and
communicating indirectly with the metal work of the lantern.
[Illustration:
Eddystone.
]
[Illustration:
Spurn Point High Light.
]
SPURN POINT HIGH LIGHT.—The Spurn High Light stands about 16 feet above
the level of the sea, and measures 100 feet to the top of the lantern.
The tower is of brick with wood floors; the roof and framing of the
lantern are of metal, seated upon a stone plinth to which it is secured;
the weathercock is surmounted by a glass repeller. An isolated conductor
of copper rod, ¾ inch diameter, is attached to the outside of the tower
rising some feet above the lantern and passing down the side of the
tower below the surface of the ground.
SOUTH FORELAND.—The South Foreland High Light stands above 300 feet
above the sea, and measures from the ground to the top of the lantern 67
feet. The tower is of brick, the lantern roof and framing are of metal
with a cast iron pedestal; the weathercock is fitted with a glass
repeller. A conductor of copper rod, ¾ inch diameter, is attached to the
outside of the tower, of the same height as the weathercock. The rod is
fastened to the lantern and tower with metal stays and fastenings, and
passes into the ground, turning off at right angles to the tower a
little below the surface. A copper flue connected with a stove in the
base of the tower, passes up the centre of the tower through the roof of
the lantern, to the lower end of which a copper rod has been attached,
which is carried to the outside of the building into the ground.
[Illustration:
South Foreland High Light.
]
The undersigned have, according to their instructions, met and
considered the circumstances under which lighthouses are placed as
respects lightning, and have arrived at the following conclusions:—
That lighthouses should be well defended from the top to the bottom.
That as respects the top, the metal of the lantern, and upwards, is
sufficient to meet every need, and satisfy every desire and fear.
That for the rest of the course down the tower, a copper rod ¾ of an
inch in diameter is quite, and more than, sufficient.
That at the bottom, where the rod enters the earth, it is desirable at
its termination to connect it metallically with a sheet of copper 3 or 4
feet long by 2 feet or more wide; the latter to be buried in the earth,
so as to give extensive contact with it.
That glass repellers are in every case useless.
That glass thimbles are not needed, but do no harm.
That if the repeller be removed, and the _point on the vane_ be
terminated as the lightning rods usually are, and then the metal of the
lantern be strongly attached to, and connected with, the upper end of
the copper rod, and the rod continued down the tower to the earth, and
the sheet of copper buried in it, such a system will be an effectual and
perfectly safe lightning conductor.
That then there need be no rod end rising by the side of, and above the
lantern.
That the rod may (if required on other accounts) come down on the inside
of the building, or in a groove in the wall; but should not be
unnecessarily removed from observation and inspection.
That all large metallic arrangements in the stonework, or other
non-metallic parts of the tower of the lighthouse, such as tying bars,
metal flues, &c., should be well connected, by copper, with the
conductor.
That the vicinity of two metallic masses without contact, or metallic
communication, is to be avoided.
That, as to the South Foreland High Light, the lantern, the central
stove, and the copper rod proceeding from it to the earth, connected as
they now are, form a perfect lightning conductor, even without the rod
that is there erected; but
That it is important casual arrangements should never be depended upon
for lightning conductors; but a copper rod be established for the
especial purpose: for, if the former be trusted to, the carelessness or
ignorance of workmen may, at after periods, upon occasions of repair or
cleansing, cause the necessary metallic connection to be left imperfect
or incomplete, and then the arrangement is not merely useless but
dangerous.
That, as to the Eddystone, it is desirable to connect the system of
wrought iron ties in it with the lightning conductor, by joining the
lower part of that iron rod which is nearest to the conductor with the
latter, by a copper rod or strap, equivalent to the conductor in
sectional area.
That the Dungeness Lighthouse is in a very anomalous condition; to
rectify which the two repellers should be removed, and also the
representative of the top of a lightning rod attached to the flue, and
that then a good copper conductor should be attached to the metal of the
lantern, upon the principles already expressed.
(Signed.) M. FARADAY.
_25th September, 1843._
* * * * *
23, GT. GEORGE STREET,
_25th September, 1843_.
SIR,
The reference, on the important subject of lightning conductors, is
to Mr. Faraday and to me. On receiving it I prepared drawings of the
buildings to which our immediate attention was required, with an
explanation of their present conductors.
These were considered at a meeting with Mr. Faraday, when he
explained the principles and their application to the several cases,
deduced from his copious experiments and scientific observations.
I have since received from him the accompanying Report for my
signature along with his, but the report is altogether Mr. Faraday’s
and therefore I prefer adding my approval of all it contains in this
separate sheet, and recommending that authority be given to me to
act upon it.
I am, Sir, &c.
(Signed) J. WALKER.
JACOB HERBERT, Esq.
_Trinity House._
* * * * *
ROYAL INSTITUTION,
_27th September, 1852_.
MY DEAR SIR,
I fortunately reached the Nash Low Lighthouse last Thursday, 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
flag-staff 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, 1843.
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 same small drain, which tends
to show how intense the discharge must have been over the whole of
the place.
Inside 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
carpet 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 ⅓ 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 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_.
EDDYSTONE LIGHT.—REPORT _of_ PROFESSOR FARADAY _on Electrical Phenomenon
which occurred thereat on the 11th January, 1853_.
ROYAL INSTITUTION,
_24th January, 1853_.
MY DEAR SIR,
In reference to the remarkable stroke of lightning which occurred at
the Eddystone Lighthouse, at midday on 11th January of this year,
and made itself manifest by a partial flash discharge in the living
rooms, I have to call your attention to the drawing herewith
returned, and to the circumstances which appear (from it) to have
accompanied and conduced to the discharge.
In the body of the stone work above the store-room exist eight rings
of metal; each going round the building, and each being four inches
square of solid iron and lead. Also, latterly the bedroom and
sitting-room have been lined with a framework of iron bars, situated
vertically, and pinned by long bolts into the stonework.
The part of the tower above the floor of the living-room is,
therefore, filled with a metallic system, which, with the metal
lantern, gives a very marked character to the upper half of the
structure.
The recent metallic arrangements (but not the rings) are connected
with the lightning rod; and the copper part of this rod, beginning
at the floor of the living-room, then proceeds downwards by the
course which can be followed in the drawing, and terminates on the
outside of the rock between high and low water marks.
Considering all these circumstances, I was led to conclude that the
conductor was in a very imperfect condition at the time of low
water; and I had little doubt that I should find that the discharge
had taken place when it was in this state, and very probably with a
spring tide.
The day of the stroke was the 11th January—a new moon occurred on
the 9th, so that it was at a time of spring tide.
The occurrence took place at midday; and, according to the tide
tables, that was close upon the time of low water at Devonport. The
end of the conductor would then be 6 feet from the water, if the
latter were quiescent, and I cannot doubt that this circumstance
gave rise to that diverted discharge which became so manifest to the
keepers. Mr. Burges, with whom I have conversed about the matter,
thinks it probable that, through the violence of the waves, the
conductor does not now descend so much as is represented in the
drawing.
I think it essential that the lower end of the conductor be made
more perfect in its action; and I should prefer this being done on
the _outside_ of the tower and rock, if the rod can be rendered
permanent in such a situation.
If it be impossible to prolong and fix the lower end of the
conductor where it now is, so that it shall have large contact with
the sea at low water, then I would suggest, whether or no, on the
more sloping part of the rock, about midway between high and low
water, three or four holes could not be sunk to the depth of 3 feet,
and about 3 or 4 feet apart, and that copper rods being placed in
these, they should be connected together, and the lightning rod
continued to them.
If this _cannot_ be done, then it might be right to consider the
propriety of the making a hole through the centre of the building
and rock, about 2 or more inches in diameter, and 30 feet deep, and
continuing the conductor to the bottom.
A conversation with Mr. Burges regarding the present state of the
Bishop’s Rock Lighthouse, now in course of construction, induces me
also to suggest the propriety of making provision for the lightning
conductor as the work proceeds.
It would be easy now to fix terminal rods of copper, and to combine
them upwards with the work. Considering the isolated and peculiarly
exposed condition of a lighthouse on this site, I would propose that
there be _two_ conducting rods from the lantern, down the outside on
opposite sides of the tower, each terminating below in two or three
prolongations, entering as proposed into the rock, or into fissures
below low water mark, so as to be well and permanently fixed.
I am, &c.,
(Signed) M. FARADAY.
THE SECRETARY,
_Trinity House_.
[The present Eddystone Lighthouse, that is the stone one erected in
1757–59 from Smeaton’s designs, has a total height from low water level
to the top of the vane of 107 feet. The annexed engraving shows two
conductors, the old and defective one passing down the left hand side
and terminating half way between high and low water level, and the
proposed new one on the right terminating in holes in the rock.—ED.]
[Illustration:
EDDYSTONE.
]
* * * * *
[The following letter would have been placed in Appendix A. along with
the replies from British Manufacturers of Lightning Conductors; but it
did not arrive until long after they had been printed off.—ED.]
Please find enclosed answer to your questions. In addition to
manufacturing rods, we have been protecting buildings with these rods
for thirty years. We sell in this way at retail from five to six hundred
thousand feet each year. We also issue a guarantee of $500 (£100) on
each building that we protect, which we hold ourselves ready to make
good in case of failure. Now, in this extensive business, we have only
had to pay one dollar damage done by lightning. We regard this as a
practical demonstration that our method of protecting buildings with
iron rods is as near perfect as it can be. There is more profit to be
made out of the copper rod, as it is made cheaply out of sheet copper,
and can be sold much higher than the iron rod. But knowing that iron for
all practical purposes is the best material for lightning rods, we feel
it to be our duty to do all we can to introduce it. We would most
respectfully ask the Conference to investigate this question as to what
kind of metal is best for rods for practical use, iron or copper. Our
own late Professor Joseph Henry pronounced in favour of iron. We have
many facts in relation to buildings being struck by lightning which we
could give at some future time if desired. We have gathered up a large
number of points that have been melted by lightning strokes. They are
melted down about ½ inch. They all look as if the same amount of heat
had been applied to each, showing very clearly that the quantity of
electricity in lightning strokes is quite uniform. We have never in any
instance known of the rod being melted, showing that the rod which we
use is of sufficient size.
* * * * *
1 & 2. We make spiral twisted iron rods weighing 45 lbs. to the hundred
feet [7¼ oz. per foot]. The rod is of the same sized material throughout
its length, except that a copper point, plated with silver and tipped
with platinum, is screwed on the upper terminal.
3. No proportion is observed between the length and sectional area.
4. Joints are made by means of copper nuts.
5. Attached to building by means of zinc strips, or a casting that fits
closely to the rod, which is screwed down.
6. The rod extends from 9 to 10 feet in the ground.
7. A circle twice the diameter of height of rod above roof.
8. All terminals on the roof are connected. There are never less than
two ground rods, and these are increased as the number of upper
terminals are increased.
We also manufacture copper rods, but do not use them where we protect
buildings, nor do we recommend them to other dealers from the fact that
our experience of thirty years has demonstrated that iron is the best
material for lightning rods.
COLE BROTHERS.
MOUNT PLEASANT,
IOWA, UNITED STATES.
* * * * *
A colliery chimney near Sunderland, 180 feet high, was struck by
Lightning, November 13th, 1878, and I was sent for to repair it. Upon
getting to the top, which was about 15 feet diameter, I found a great
many of the bricks displaced, and the upper terminal of the conductor
(which was a tube 0·50 in. internal, and about 0·62 in. external
diameter, and which had stood about 1 foot above the top of the chimney)
had been fused and was lying on the top of the chimney, it was quite
brittle, and easily broken by the hand. The upper 10 feet of ½ inch wire
rope was in a similar state; it seemed as if it had been passed through
an exceedingly hot furnace, and I rubbed it to dust in my hands. This 10
feet length was above the first holdfast, below the holdfast the wire
rope was perfectly good. The holdfast was one of those which are driven
into a wooden plug let into the wall and pinned tightly down on the
rope, which had been badly bruised in the fixing—in fact, knocked almost
flat. I believe that this was the cause of the accident, and that the
lightning travelled down as far as this holdfast, and there meeting
obstruction, returned destroying the wire and rod and shattering the
brickwork. The earth connection was good, the end was buried in a trench
2 feet deep and 15 feet long.
T. MASSINGHAM.
NEWCASTLE-ON-TYNE.
* * * * *
I have been in communication with several of the principal brick
builders here by whom the great majority of the chimney stalks in
Glasgow and the west of Scotland are erected, and I believe the
following statements may be taken as correct:—
(1) Very few stalks under ninety feet in height have lightning
conductors, but, _as a rule_, the higher stalks have conductors. One of
my correspondents says that “this rule holds good in four cases out of
five.”
(2) A chimney being struck by lightning is an extremely rare occurrence
in this district. One builder of long experience (Mr. McDonald) says, “I
have known of several stalks that were struck by lightning, that had no
conductors. I cannot point to one that was struck by lightning and had a
conductor.” Another firm of old standing (Allan and Mann) say—“In our
experience we have not known of a chimney stalk, with lightning
conductor fixed, damaged by lightning.” Another firm (Bell, Hornsby and
Co.) say—“In our experience we have not known an ordinary stalk with or
without a conductor struck by lightning,” and Mr. Goldie says—“During
the last twenty years I can remember only one such case,” and he is not
sure whether the stalk had a conductor or not. There are three cases
known to have occurred in Glasgow, but I never heard of any others among
the hundreds—I may say thousands—of chimneys which are here. The great
stalk at St. Rollox was struck shortly after its erection. A stalk at
the works of Messrs. Alexander Paul and Co., was struck about nine years
ago. Mr. Goldie makes the remark—and I think it is well worthy of
notice—that in all these cases the accident happened shortly after the
completion of the stalk. In these circumstances the stalk would still,
no doubt, contain a large amount of moisture.
I think the St. Rollox stalk had a conductor fixed before it was struck,
but I am not aware whether either of the others had.
Mr. Higginbotham (Todd and Higginbotham) tells me that the stalk at
their works was struck before it was quite completed. It was _very
slightly_ injured. It was afterwards struck as mentioned in my letter.
On that occasion it had a lightning conductor.
The damage done was not very serious, but necessitated the binding of
the stalk with numerous iron hoops—as thus strengthened it still stands.
Mr. Higginbotham says that the opinion at the time was that the
conductor saved the stalk from complete destruction, but that it was too
small.
They, therefore, had it replaced by a much heavier one—copper rope ⅜th
of an inch diameter, kept 1½ inches from the brickwork by glass
insulators—which still remains.
J. HONEYMAN.
140, BATH STREET, GLASGOW.
* * * * *
There was no lightning conductor of any kind at Wells Church. The
electric fluid struck the east side of the Tower just above the ridge of
the nave roof. The tower stands, or stood, at the west end. I enclose an
account of the fire from a local paper:—
WELLS.—TOTAL DESTRUCTION OF THE CHURCH.—“Near midnight of Saturday last,
August 2nd, 1879, a terrific thunderstorm burst over this town and a
large district around, causing most intense alarm and unfortunately
ending in sad disaster. The storm raged throughout the night, and was
accompanied in many places by a perfect deluge of rain. Between three
and four a.m. of Sunday, the 3rd, it appeared to reach its height, the
lightning being of a most vivid and alarming nature, and the thunder
reverberating in continuous peals. A lull then occurred, but between
five and six a.m. the storm again burst out with great fury, and at 5.50
the electric fluid struck the church on the eastern face of the tower
immediately above the apex of the roof, driving out a large portion of
the stone work, the flints flying hundreds of feet around. One large
stone fell upon the roof of a house, near the east window, and
penetrated to the room below, which was fortunately unoccupied; but the
tenant, Mr. R. Wharf, who slept in the next room, was aroused, and one
or two persons in the road seeing what had occurred, and observing smoke
directly after issuing from the roof of the church, raised an alarm of
fire, which quickly awakened the whole town.
R. M. PHIPSON.
NORWICH.
* * * * *
The first visible injury to Wells Church was the “skinning” of a portion
of the tower (about 10 feet high by 5 feet broad) extending downwards
from the east window of the tower (_i.e._, the window which looked over
the roof of the nave,) to the point at which the lead-covered nave
joined the tower. The lightning is believed to have set fire to the roof
at this point, and also to have travelled along the lead roof to the
chancel, and in crossing the vestry to have ignited the surplices, as
the church was seen to be on fire at both ends before the middle was
touched. The “skinning” was accompanied by great disruptive force, as
the stones from the tower were not only shot the full length of the
church, but one large one fell on the roof of a house 60 feet beyond the
east end of the church.
WELLS, NORFOLK.
F. LONG.
* * * * *
As your questions in the _Times_ of to-day allude only to protection to
_buildings_ from lightning, I need not say anything on the perfect
protection afforded to Her Majesty’s ships by the conductors of Sir Snow
Harris, from the time they were used in every ship in the service.
H.M.S. “Beagle,” Commander FitzRoy, was one of the first ships fitted
with them. At Monte Video a heavy shock of lightning passed down the
mainmast and through the ship without doing the slightest injury; but as
the vane staff which tapered to a fine point, was fused at the point, it
enables me to answer one of your questions. The copper was melted till
the diameter was about one eighth of an inch, but below that point the
conductor was not injured in any way.
You will like to know a case in which a copper wire acted as a perfect
conductor, _though fused throughout its length_. It was at Monte Video,
in the house of the English Consul, a flag-staff was struck, and
conducted the lightning through a flat roof, near the bell wire of a
suite of rooms (the wire ran in sight near the cornice) through a hole
in each dividing wall, and then down to the bell in the basement; the
wire was melted into drops like shot, which burnt a row of small holes
in the carpet of each room. A dark mark, on the cornice above, showed
where the wire had been. At the bell there was a slight explosion, and
some little damage, but I do not recollect whether anything acted
partially as a conductor from that point, and so carried off that part
of the charge.
This, I think, shows that even an ordinary bell wire will act as a
conductor for a rather strong stroke of lightning, as the large
flag-staff was shattered.
I am anxious to call the attention of your conference to a point that it
will be interesting to clear up. That is, whether a conductor should be
a _solid_ rod, or in a shape to give the largest amount of _surface_ in
the section? When I tell you that Faraday and Harris each told me that
the other “knew nothing about it,” because they differed entirely on
this point, I think you will see the importance of it. I had at the time
to approve of the conductors for lighthouses. I will, if you wish it,
give you more particulars on this point, as I believe it has never yet
been settled: lighthouses having been fitted with Faraday’s, and ships
and public buildings with Harris’ conductors. The one being a solid
bolt, the other a hollow tube or double thin plates.
If Harris was right there is an unnecessary amount of copper in
Faraday’s solid conductors; if Faraday is right, there is an unnecessary
outlay in putting a given amount of copper into the shape of a tube,
instead of using it as a solid rod.
B. J. SULIVAN, _Admiral_.
P.S.—You should get from the Trinity House particulars of a case in
which, with a good solid conductor, the iron floor of a lighthouse,
aided by some lead in the wall, diverted the lightning from the
conductor, and caused damage inside. I think it was a Portland
lighthouse, but it is so many years since that I may not be right.
TREGEN, BOURNEMOUTH.
* * * * *
Three or four years since, I was looking out of my office window in
Finsbury, when a flash of lightning struck the tower of the church of
St. Giles’, Cripplegate, towards which my sight happened at the time to
be directed. As a portion only of the flag-staff, placed at one corner
of the tower, was destroyed, I obtained permission to ascend the tower
and discover the reason. I found a substantial copper rope conductor
fixed in a somewhat careless fashion to the back of the tower, and
passing some distance into the earth. This copper rope was about an inch
in diameter, and was carried upwards, under and over several projections
and cornices, and across the roof of the tower to its centre—where it
stood erect, and evidently did its assigned work admirably. Clumsy and
unsatisfactory as the fixing of this bent copper rope seemed to me to
be, it is quite certain that it was most efficient; and had it not been
for the flag-staff, capped with lead, which was carried up considerably
higher than the copper rope, no evidence whatever of the lightning’s
path would have been revealed. As it was, the discharge of lightning
struck the leaden cap of the flag-staff, and descended down the wet,
wooden pole, until the summit of the copper-rope conductor in the centre
of the tower was reached, when the discharge flew across to the metallic
earth conductor, leaving the lower part of the flag-staff unhurt, but
shattering to splinters that portion which was higher than the summit of
the copper rope.
RICHARD HERRING.
27, ST. MARY’S ROAD, HIGHBURY.
* * * * *
A small public-house of mine (the “Wheatsheaf”) stands at Trolley
Bottom, in the parish of Flamstead, between St. Albans and Dunstable. On
Wednesday, August 6th, 1879, about 2 p.m., during a storm, not otherwise
very severe, my tenant was seated by the tap-room window (A on the plan)
his wife being seated opposite to him, and having the window on her
left, whilst she held her child with her right hand; there were at the
same time in the room about five men besides. A sharp flash of lightning
occurred, and the poor woman (when the smoke cleared away) was observed
to have fallen backwards. She gasped twice, never spoke, and died
immediately, and bore no further mark of injury, I understand, than a
slight mark as of scorching on her neck, below the left ear. I fail to
recollect whether her clothing was scorched or not, the child’s shoe and
sock were both burnt, but she, herself, was unharmed. All present were
sensible of an atmosphere heavily laden with sulphurous fumes; but,
excepting as above, were absolutely unhurt.
On visiting the house about a week afterwards, with a view to its
repair, I found a small round hole as if made with a bullet in a pane of
the window (A) close to which the woman was sitting, but could discover
no further injury either to the other panes, the window-frame, the
floor, or anything in the room. In the parlour, B, the window-frame was
violently wrenched outwards two or three inches, several of the panes
were broken, one sash-line being scorched, as also the frame and linings
in places, especially in the neighbourhood of the sash-weights (iron).
The wooden chimney-piece E, was slightly moved from its position, the
various articles upon it were scattered, and a bottle of ink which stood
there, was thrown with some violence to the ceiling. The upper part of
the chimney to that room, G, and a portion of the wall, of which it was
a part, forming the gable end to the house were shattered, and at H a
stout post, contiguous to the house wall, and supporting the roof of a
lean-to, was split and wrenched from its position. The windows and
frames upstairs, C D, were in the same state as that at B. The chimney,
K, to the tap-room, was quite uninjured, and no harm was done to any
part of the back of the house.
[Illustration:
ELEVATION. PLAN.
]
Flamstead is about four miles from Luton, and six from St. Albans, and
stands on high land. Trolley Bottom is a hamlet half-a-mile distant, and
is, as its name implies, low-lying. My house is, perhaps, the lowest in
position there. It faces the North-West.
I fear that my experiences will be found to have but little bearing upon
the main point you have in view, viz., the comparative merits of
different descriptions of Lightning Conductors. I venture to think,
however, that they are not altogether without interest as illustrating
the effects of lightning in a by no means exposed situation.
I am writing only from memory what was told me at the time, and should
you desire further information on any points, shall be happy to
endeavour to obtain it for you.
It would interest me very much to know how it is to be accounted for
that, whilst in the room in which the poor woman was struck, no further
damage was done, other parts of the house were, comparatively speaking,
wrecked.
JOHN EDWARD GROOME.
KING’S LANGLEY.
* * * * *
I was in a house at Cannes (France) belonging to my late father on the
occasion of its being struck by lightning about five or six years ago.
The storm in which it occurred was a very short one, consisting of only
four explosions, _every one_ of which took effect on some building in
Cannes.
The rain was falling in torrents, and to this I consider we owed our
safety as the shoots and stack-pipes being full of water acted as
conductors. The villa stood high, but another building _very_ much
higher, and on higher ground, was within 100 yards. The lightning struck
the metal cowl of a brick chimney, which, being an addition, was led
down outside the walls of the house.
In the explosion the front of the grate of the room to which this
chimney belonged, together with fire-irons, &c., were all projected
across the room (a large one), about 30 feet; but no marks of lightning
having entered the room were apparent. In fact the lightning after
blowing up this chimney, together with much of the roof and wall of the
house (great portions of the solid masonry of which I found 50 and 60
yards off!) appears to have left the chimney and, taking the course of
the iron shoot round the house, to have divided into _three_ streams,
each of which ultimately found its way down a separate stack-pipe,
melting in its way all the soldering of the joints, but otherwise
leaving them uninjured.
One stream passed thus into a well, the door of which (locked the night
before) was burst open, I presume by the sudden expansion of the air,
another stream of the electric fluid passed into an underground drain,
which it burst up, hurling into the air the trees planted above it, the
third passing across a level asphalt roof, which it melted in spite of
the water lying on it, descended into the earth harmlessly.
You will see by this that the amount of electric fluid must have been
very great to require all these modes of dispersion, and it suggests the
question whether the diameter of the ordinary conductors would be
sufficient to carry off so great a stream. Of course, in this case,
there was no conductor, and therefore no means of testing it.
H. RADCLIFFE DUGMORE.
THE LODGE,
PARKSTONE, DORSET.
* * * * *
Thank you very much for the Pamphlet, which I have read with great
interest. Messrs. W. & W. (page 6) state that conductors in masts (like
Harris’s) are “most objectionable.” The best answer to that is: that
while ships were struck in the Navy, and lives lost every year before
they were introduced, no ship fitted with them ever received the
slightest damage; and since all ships were ordered to be fitted—now
about 30 to 35 years—I have never heard of the slightest damage, or the
loss of one life—that fact upsets all theories on the subject!
Then connections between the higher and lower masts, and especially at
right angles, are objected to on the ground that at a bend the conductor
may be fused; such a thing was never heard of in the thousands of
conductors that must have been fitted in the navy. Even if the movable
plate were turned back the lightning following the longest conductor
would leave one mast for the other, as the conductor went right over the
mastheads, and the two conductors nearly touched each other.
At Spring Grove, near Isleworth, the church had a high spire which was
fitted with a conductor, but the Vicarage was struck and some damage
done to it, though, I think, much nearer to the tower than its height. I
believe many are contented with one or two conductors to a building that
should have many more. My small house here is about 70 feet long by 38
feet wide, and I have seven conductors—one to each chimney.
If it is once decided beyond dispute, that copper conducts in proportion
to its _volume_; then a rod, or flat-plate, of about the proportions of
one to four or five, for the purpose of fitting closer round
projections, would be the cheapest and simplest form; but if it conducts
in proportion to _surface_ then of course a tube, _double_ plate, or
wire rope, would give the greatest protection at a given cost.
I firmly believe in the surface theory of Harris. I had been with him
often when he made experiments nearly fifty years since, and witnessed a
strip of tin foil of the thinnest kind, and about ¼ inch wide, protect a
model mast of about six inches in diameter from electric shock, that
without it split the mast to pieces, aided by a small hole through its
centre filled with gunpowder. And I always thought that the
surface-conducting theory of Harris was indisputable. But about 20 years
since, having to approve a proposal of the Trinity House for a new
conductor of a Lighthouse, which, like previous ones, was an inch in
diameter copper rod called “Faraday’s Plan,” I thought I would go up to
the Royal Institution and ask him why he did not use a copper tube
instead, giving much greater conducting power with less copper. I did
so, and he asserted positively that the conducting power depended
entirely on the volume of copper in the section of the conductor, no
matter whether it was in a bolt, plates, or tube; and that if Harris
said differently, “He knows nothing whatever about it;” of course, I
approved the rod conductor. But singularly enough, though I had not seen
Harris for years, he came to town a few days after, and came to the
Board of Trade to see me, and bring me a piece of his large tube
conductor, with a connection, that he was fitting to the Houses of
Parliament. When I told him what Faraday’s opinion was, he answered,
“Then he knows nothing about it.” I was still inclined to believe in
Harris; but a few years after, a young Indian R.E. Officer—Lieut.-Col.
Stewart—whose death not long after was a serious loss to the service,
was sent home to procure the electric cables for connecting different
Indian ports. I was asked by the Secretary of the Indian Office to give
him all the help I could. One day he came to me with a piece of the
cable he proposed using. Inside the iron wires was a single stout copper
wire about ⅒ of an inch in diameter. I asked him why he had not the
central wire of several strands as usual, as I believed it would greatly
increase the conductive power. He said that he had _carried out a number
of experiments on this point_ before deciding; and that he was satisfied
the conducting power depended on the _amount_ of _copper_ in the
conductor, and consequently a solid wire was better than one of the same
size made up by twisting small wires together.
This of course shook my confidence in Harris’ theory; but it is a point
that can be easily decided by experiments on a larger scale; and I hope
your Committee will be able to decide it finally.
Messrs. W. & W. prefer to a conductor on the masts a wire rope carried
down from the truck, stopped to a back stay. The following fact will
show its danger:—A French frigate, some fifty years since, had one so
fitted as an experiment; while striking T.G. masts the conductor formed
a large bight as the mast was lowered; a man standing on cap or
cross-trees—I forget which—formed a shorter conductor between two parts
of the wire rope and was killed without any other damage being done.
B. J. SULIVAN.
BOURNEMOUTH.
* * * * *
With reference to your recent letter in the “Times,” I shall be glad if
you will inform me whether there has come under the consideration of the
Conference the question of lightning conductors on board iron ships with
_iron_ masts; for my part they would seem to be useless, and that if the
iron mast have sufficient metallic communication, through the bottom,
with the outside of the ship either by means of the screw shaft or in
some other way; no additional conductor, copper ribbon, or strip, down
the masts and along the decks over the ship’s side, or copper tube down
the shrouds and over the ship’s side could be of the slightest benefit.
In some ships one or other of these arrangements has been adopted, and
in others both have been applied at same time.
C. M. L. McHARDY.
FERN HILL COTTAGE, WINDSOR FOREST.
* * * * *
I have observed your letter in “The Architect” of Saturday last. With
reference to the subject on which it treats, I chance to have noticed
since my residence here (a period of eight years) what I suppose to be
an unusual frequency of lightning striking objects immediately round
this spot, and the neighbourhood generally.
This inference is suggested by the fact that within the period mentioned
lightning has fallen within fifty yards of the same spot three
times—that this summer (one of those occasions) two other houses, both
(say) within 500 yards in a direct line from this spot, were also
struck—and generally, I believe, more objects are struck in this
neighbourhood than usually happens to be the case.
My idea may be a fallacy, for I have no sort of statistics by which to
test it; but if you suppose it is not so, and if such points come within
the scope of your inquiry, I should be glad to send you a map marked
with the spots where, and the dates when, lightning has fallen in or
near this town. The only local peculiarities I notice are: 1. An unusual
number of houses close to this have lightning conductors (a mere
coincidence, and not placed there on any impression like my own). 2. We
are at the bottom of a deep bay of parabolic plan which may influence
the movements of electrical disturbance. 3. A soil of sand and gravel
containing much oxide of iron.
A. BALDRY.
ATHELNEY, BOURNEMOUTH, HANTS.
[Mr. Baldry kindly supplied the map, and we find that a half circle of
half a mile radius struck from the cliff-edge half a mile west of
Bournemouth Pier includes the churches of St. Peter, with one conductor,
and Holy Trinity with three; eight private houses with conductors, of
which four houses have one each, and the other four have two, five, six
and seven respectively, and within this area six objects are known to
have been struck—three in the year 1879, two in 1871, and one in 1870.
We do not know of any English locality where there are so many houses
with conductors; but there are many more remarkable cases of repeated
injury within small areas—_e.g._, in one storm in June, 1878, there were
at least eight separate buildings injured within a circle of half a mile
radius struck from the Metropolitan Cattle Market in the north of
London.—ED.]
* * * * *
It occurs to me that it is worth while for the delegates of the Royal
Institute of British Architects to raise the question, and, if possible
settle, whether or not the gas pipes which permeate many buildings might
or might not be utilized as lightning conductors; and whether any risk
of gas explosion would be incurred thereby.
In my own practice there occurred the case of a lofty building, with a
domed roof, and a sun-burner with a 1½ inch gas-pipe to supply it,
rising to the summit of the dome, and a large iron cowl over the
sun-burner.
The same circumstance occurs in most modern theatres. If the cowl were
struck by lightning there was perfect metallic connection thence to the
street gas mains—and one of larger sectional and superficial area than
an ordinary lightning conductor would give.
H. D. DAVIS.
2, FINSBURY CIRCUS, CITY, E.C.
* * * * *
Lightning conductors have been a great hobby with me for many years, and
I have induced a great number of clergymen and others to fix them to
their towers and houses. During my time in the navy and merchant service
I witnessed many fearful effects of lightning, and for the last thirty
years I have been striving to persuade my friends to secure their houses
from these terrific visitations. On the 24th December, 1699, the upper
half of the fine steeple of this town was hurled to the ground, and a
large portion of the church broken in. Pinnacles were then substituted
for the upper portion of the steeple, to which I have had an efficient
conductor attached. As far as I can gather from records, and from the
abortions so frequently substituted for the original pinnacles of
towers, I have come to the conclusion that _nearly every tower in this
country_ has been struck by lightning during the last 400 years, when
nearly all the towers were built. Many years since, the Illustrated News
gave a sketch of a beautiful steeple (in Norfolk, I believe) destroyed
by lightning. It was stated that this was the second steeple which had
met with so sad a fate. After the destruction of the first, a second
steeple was built by subscription, at a cost of £1,000, and the
scaffolding had been removed only ten days when, during a terrific
thunderstorm, this second steeple was entirely destroyed! I wrote
immediately to the incumbent to ask about the _conductor_, and his
answer was that none had been fixed, but that it was quite decided that
an efficient one should be attached to _the third steeple_! This would
almost appear incredible, and I regret that I did not dot down the name
of the Parish and other data, but I think it was about 20 years since.
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.
[Illustration: Plan and Elevation of washhouse of Middlesboro’ Fever
Hospital]
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.
[Illustration: Plan and Elevation of Indian Pagoda]
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.
[Illustration:
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.
[Illustration:
D
]
[Illustration:
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.
[Illustration: Sections of Rod at Upwood Gorse, Caterham]
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.
[Illustration: Sections of Munson’s Rods]
[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.
[Illustration:
FIG. 1.
]
[Illustration:
FIG. 2.
]
[Illustration:
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.
[Illustration:
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.
[Illustration:
SOUTH-EAST VIEW OF BOOTHAM BAR.
]
ACCIDENT AT BOOTHAM BAR, YORK.
[Illustration:
VIEW OF HOUSE AND SECTION OF BAR.
]
[Illustration:
GROUND PLAN OF HOUSES AND OF BAR.
]
REFERENCES.
A Gas bracket struck.
B Iron sheathed portcullis.
C Old gas bracket.
D Old Iron brackets.
APPENDIX J.
DATA RESPECTING THE SECTIONAL AREA OF METAL REQUISITE FOR LIGHTNING
CONDUCTORS.
(N.B.—In order to avoid confusion, all areas of iron have been reduced
to ⅙th of their actual sizes, so that virtually tables I. and II.
may be regarded as giving all details for _copper_—but the metal
is specified in each case.)
TABLE I.—LIST OF METALS MELTED.
───────────────────┬────┬─────────────────┬────────────────────────────
Material │Form│ Size │ REMARKS
───────────────────┼────┼─────────┬───────┼────────────────────────────
│ │Diameter.│Area of│
│ │ │Copper.│
───────────────────┼────┼─────────┼───────┼────────────────────────────
│ │ in. │ in. │
COPPER │Rod │·35 │·10 │Duprez, App., p. 92
COPPER │Rope│·31 │·075 │At Nantes, Callaud’s
│ │ │ │ _Traité_, p. 89
[6]_Not Specified._│Rope│ │·07 │At Carcassone, Callaud’s
│ │ │ │ _Traité_, p. 89
IRON │Rod │ │·03 │Harris on Thunderstorms, p.
│ │ │ │ 109
BRASS │Rod │·20 │·03 │Duprez, App., p. 92
COPPER │Rod │·13? │·01? │Sullivan, App., p. 195
───────────────────┴────┴─────────┴───────┴────────────────────────────
Footnote 6:
Assumed to have been Iron, the dimension given is “18 mm.” = ·70 in.
diam., or ·38 in. area.
TABLE II.—REMARKS RESPECTING DIMENSIONS.
───────────────────┬────┬─────────────────┬────────────────────────────
Material │Form│ Size │ REMARKS
───────────────────┼────┼─────────┬───────┼────────────────────────────
│ │Diameter │Area of│
│ │ │Copper.│
───────────────────┼────┼─────────┼───────┼────────────────────────────
│ │ in. │ in. │
COPPER │Rod │ │·61 │Trinity House smallest,
│ │ │ │ App., p. 183
COPPER │Rod │·75 │·44 │Will carry any flash, Harris
│ │ │ │ on _Thunderstorms_, p. 115
COPPER │Rod │·50 │·20 │Never yet failed, Faraday,
│ │ │ │ App., p. 89
COPPER │Tube│ │·20 │War Office smallest, App.,
│ │ │ │ p. 70
COPPER │Tape│ │·19 │Gray & Son’s smallest, App.,
│ │ │ │ p.
IRON │Rod │ │·16 │Never affected, Franklin,
│ │ │ │ App., p. 52
COPPER │Any │ │·11 │Recommended by Phin, App.,
│form│ │ │ p. 103
IRON │Rod │ │·11 │More than sufficient, Gay
│ │ │ │ Lussac, App., p. 58
COPPER │Rope│·38 │·11 │Recommended by Callaud,
│ │ │ │ App., p. 104
COPPER │Tape│ │·09 │Freeman & Collier’s
│ │ │ │ smallest, App., p. 10
IRON │Rod │ │·08 │Never known to be melted,
│ │ │ │ Pouillet, App., p. 62
IRON │Rod │ │·08 │Should not be less, Henry,
│ │ │ │ App., p. 99
COPPER │Rope│·39 │·06 │Carried off heavy discharge,
│ │ │ │ Callaud _Traité_, p. 89
IRON │Rod │ │·06 │Recommended by Callaud,
│ │ │ │ App., p. 104
IRON │Rod │ │·06 │Recommended by Mohn, App.,
│ │ │ │ p. 107
COPPER │Rod │·25 │·05 │Recommended by Mohn, App.,
│ │ │ │ p. 107
IRON │Rod │ │·04 │Recommended by Phin, App.,
│ │ │ │ p. 103
COPPER │Rod │·20 │·03 │Recommended by Zenger, App.,
│ │ │ │ p. 106
IRON │Rope│ │·02 │Recommended by Mann, App.,
│ │ │ │ p. 108
IRON │Wire│ │·01 │Sufficient for any house,
│ │ │ │ Preece, App., p. 101
───────────────────┴────┴─────────┴───────┴────────────────────────────
DIMENSIONS OF LIGHTNING RODS—COPPER.
_Partly extracted from the Appendix at the pages quoted, and partly
compiled from specimens collected by the Conference, and from trade
circulars._
────────────┬────────┬───────┬─────────┬───────────┬────┬──────┬────────────
│ │ │ │ │ │Weight│Remarks, and
Pattern │Diameter│Breadth│Thickness│Superficies│Area│ per │ References
│ │ │ │ │ │ foot │ to
│ │ │ │ │ │ │Appendices.
────────────┼────────┼───────┼─────────┼───────────┼────┼──────┼────────────
│ Inches │Inches │ Inch │ Inches │Inch│ oz. │
│ │ │ │ │ │ │
│Ext. 1½ │ │ │ Ext. 4·71 │ │ │Sir W. Snow
TUBE │ Int. 1 │ │ ¼ │ Int. 3·14 │ ·98│ 60│ Harris
│ │ │ │ │ │ │ (49)
│ │ │ │ │ │ │
│ │ │ │ │ │ │Trinity
HEMICYLINDER│ 1½ │ │ │ 3·86 │ ·88│ 54│ House,
│ │ │ │ │ │ │ Mains
│ │ │ │ │ │ │ (183)
│ │ │ │ │ │ │
│ │ │ │ │ │ │Trinity
HEMICYLINDER│ 1¼ │ │ │ 3·21 │ ·61│ 37│ House,
│ │ │ │ │ │ │ Branches
│ │ │ │ │ │ │ (183)
│ │ │ │ │ │ │
│ │ │ │ │ │ │Freeman &
TAPE │ │ 3 │ 3/16 │ 6·38 │ ·56│ 34│ Collier’s
│ │ │ │ │ │ │ largest
│ │ │ │ │ │ │ (10)
│ │ │ │ │ │ │
TUBE │Ext. 1½ │ │ ⅛ │ Ext. 4·71 │ ·54│ 33│
│Int. 1¼ │ │ │ Int. 3·93 │ │ │
│ │ │ │ │ │ │
│ │ │ │ │ │ │Faraday
│ │ │ │ │ │ │ preferred
ROD │ ¾ │ │ │ 2·35 │ ·44│ 27│ this to
│ │ │ │ │ │ │ smaller
│ │ │ │ │ │ │ (89)
│ │ │ │ │ │ │
│ │ │ │ │ │ │Gray & Son’s
TAPE │ │ 3 │ ⅛ │ 6·25 │ ·37│ 23│ largest
│ │ │ │ │ │ │ (7)
│ │ │ │ │ │ │
TUBE │ Ext. 1 │ │ ⅛ │ Ext. 3·14 │ ·34│ 21│
│ Int. ¾ │ │ │ Int. 2·36 │ │ │
│ │ │ │ │ │ │
│ │ │ │ │ │ │Sanderson’s
TAPE │ │ 2 │ ⅛ │ 4·25 │ ·25│ 15│ largest
│ │ │ │ │ │ │ (23)
│ │ │ │ │ │ │
TAPE │ │ 1½ │ ·15 │ 3·30 │ ·23│ 14│
│ │ │ │ │ │ │
│ │ │ │ │ │ │War Office
│ │ │ │ │ │ │ (70)
ROD │ ½ │ │ │ 1·57 │ ·20│ 12│ Sir W.
│ │ │ │ │ │ │ Snow
│ │ │ │ │ │ │ Harris
│ │ │ │ │ │ │ (49)
│ │ │ │ │ │ │
│ │ │ │ │ │ │War Office
│ │ │ │ │ │ │ (70)
TAPE │ │ 1½ │ ⅛ │ 3·25 │ ·19│ 12│ “Smallest
│ │ │ │ │ │ │ desirable”
│ │ │ │ │ │ │ Gray & Son
│ │ │ │ │ │ │ (7)
│ │ │ │ │ │ │
TUBE │ Ext. ⅝ │ │ ⅛ │ Ext. 1·96 │ ·20│ 12│War Office
│ Int. ⅜ │ │ │ Int. 1·18 │ │ │ (70)
│ │ │ │ │ │ │
TAPE │ │ 2½ │ 1/16 │ 5·12 │ ·15│ 9│J. Davis &
│ │ │ │ │ │ │ Son (14)
│ │ │ │ │ │ │
ROPE (49 │ │ │ │ │ │ │Pennycook &
square │ ⅔ │ │ │ 10·78 │ ·15│ 9│ Co.
wires) │ │ │ │ │ │ │
│ │ │ │ │ │ │
TAPE │ │ 2 │ 1/16 │ 4·12 │ ·13│ 8│
│ │ │ │ │ │ │
TAPE │ │ 1 │ ⅛ │ 2·25 │ ·13│ 8│Phin, of New
│ │ │ │ │ │ │ York (103)
│ │ │ │ │ │ │
│ │ │ │ │ │ │{Massingham
ROPE (49 │ ½ │ │ │ 8·00? │ ·10│ 6│ (15)
wires) │ │ │ │ │ │ │ Newall’s
│ │ │ │ │ │ │ Rope
│ │ │ │ │ │ │
TAPE │ │ 1½ │ 1/16 │ 3·12 │ ·09│ 6│
│ │ │ │ │ │ │
│ │ │ │ │ │ │Freeman &
TAPE │ │ ¾ │ ⅛ │ 1·75 │ ·09│ 6│ Collier’s
│ │ │ │ │ │ │ smallest
│ │ │ │ │ │ │ (10)
│ │ │ │ │ │ │
│ Ext. ⅞ │ │ │ Ext. 2·75 │ │ │
TUBE │ Int. │ │ 1/32 │ Int. 2·55 │ ·08│ 5│
│ 13/16 │ │ │ │ │ │
│ │ │ │ │ │ │
ROPE (36 │ │ │ │ │ │ │
wires & │ 7/16 │ │ │ 5·00? │ ·08│ 5│J. Davis &
hemp │ │ │ │ │ │ │ Son (14)
centre) │ │ │ │ │ │ │
│ │ │ │ │ │ │
SPRATT’S │ │ │ │ │ │ │
PATENT │ │ 1⅓ │ │ 4·52 │ ·08│ 5│
PLAIT (20 │ │ │ │ │ │ │
wires) │ │ │ │ │ │ │
│ │ │ │ │ │ │
TAPE │ │ 1 │ 1/16 │ 2·12 │ ·06│ 4│
│ │ │ │ │ │ │
ROPE (49 │ ⅜ │ │ │ 6·00? │ ·06│ 4│Newall’s
wires) │ │ │ │ │ │ │ Rope
│ │ │ │ │ │ │
│ │ │ │ │ │ │Sanderson’s
TAPE │ │ ⅝ │ 1/12 │ 1·42 │ ·05│ 3│ smallest
│ │ │ │ │ │ │ (23)
│ │ │ │ │ │ │
SPRATT’S │ │ │ │ │ │ │
PATENT │ │ 1 │ │ 3·16 │ ·05│ 3│
PLAIT (14 │ │ │ │ │ │ │
wires) │ │ │ │ │ │ │
│ │ │ │ │ │ │
HART’S PLAIT│ │ │ │ │ │ │
(13 copper│ │ │ │ │ │ │
wires and │ │ │ │ 3·08 │ ·05│ 3│
1 zinc │ │ │ │ │ │ │
one) │ │ │ │ │ │ │
────────────┴────────┴───────┴─────────┴───────────┴────┴──────┴────────────
APPENDIX K.
NOTES RESPECTING LIGHTNING CONDUCTORS, COLLECTED IN PARIS IN MAY, 1881,
BY MESSRS. PREECE & SYMONS.
The information which we obtained may perhaps be most conveniently
grouped under the names, arranged in alphabetical order, of the
authorities whose opinions or whose practice we quote. These gentlemen
are M. Androuët, who, under the direction of M. Alphand, the City
Engineer, has charge of all the lightning conductors attached to the
municipal buildings of Paris, M. Borrel, of 47, rue des Petits Champs,
who has been making lightning conductors nearly all his life, M. le
Comte du Moncel, who is well known as perhaps the highest authority in
France upon the practical application of electricity, and lastly M.
Jarriant who is manufacturer to the municipality, and also, we believe,
to the War Department, besides having a large connection among
architects and engineers.
* * * * *
M. ANDROUËT accompanied us in a thorough examination of the conductors
as they are now fixed upon the south gallery of the Louvre, temporarily
occupied as the Hotel de Ville de Paris. They were stated to be only
temporarily fixed, because the offices of the Préfet of the Seine will
be removed to the new Hotel de Ville as soon as it is rebuilt, but they
were said nevertheless to be in almost all respects conformable to the
instructions issued by the municipality. The _tiges_ were iron rods, 10
m. (33 feet) high, with rather blunt terminals of gilded copper; they
were 35 m. (115 ft.) apart. All were united by a horizontal copper rope,
½ inch diameter (used instead of iron bars 0·8 in. square, because of
the temporary nature of the work), which was led along the roof through
iron holdfasts or crutches, which were carefully soldered to the metal
roof. All joints in the rope were spliced and heavily soldered. For
æsthetic reasons the main conductor is carried down _inside_ the
building, through various closets, &c., and finally, after a rather
circuitous course, it finds its earth terminal in a plate of copper 1 m.
(3 ft. 3 in.) square, immersed in the Seine. Although the roof is well
covered with metal no separate connections with earth are made. M.
Androuët tests the conductivity from every _tige_ in the spring of each
year, using a very portable apparatus, consisting of two Leclanché’s
cells and a trembling bell.
* * * * *
M. BORREL showed us various specimens of conductors, of earth terminals,
and also his portable testing apparatus. He also gave us a copy of the
_Instruction sur les Paratonnerres_, which he issues, and from which we
make a few extracts, especially as in several respects M. Borrel’s views
are expressed with unusual clearness, and although in holding some of
them he stands alone:
“A lightning conductor is a preventive agent destined to convey to moist
earth, or preferably to water, the electricity contained in a cloud.
When strong earth tension is produced by the passage of an oppositely
electrified cloud, the beneficial action of the conductor is indicated
by the luminous brush discharge from the top of the conductor.
“It is generally considered that a conductor protects a cone of
revolution, having for its base the height of the point above the roof
multiplied by 1·75, and for its summit the point. If, therefore, the
point be 6 m. (20 ft.) above the roof, it will protect a base 10½ m. (35
ft.) radius. M. Borrel supplies round upper terminals of galvanised
wrought iron about 10 m. (33 ft. high), and tapering from a diameter of
4 inches at the base to ¾ inch at the top.
“Having found that long exposure to the weather destroys iron wire
ropes, and even copper ones, if made of many small wires, he has adopted
where ropes are necessary, four or five rods nearly 0·20 in. diameter,
so slightly twisted as not to strain the metal. By this means the
numerous interstices of the ordinary ropes are avoided, and much greater
durability is insured.
“Where iron bars are used he employs galvanised wrought iron in square
bars, the sides ranging from 0·63 in. to 0·90 in.
“To allow for variations of length produced by changes of temperature,
he always inserts, in long roof conductors, a compensator, which is
merely a loop of copper tape.
“M. Borrel says that it is especially upon the earth connection that the
efficacy of a conductor largely depends; there must be a metallic mass,
with a large surface, and he describes his pattern of ‘_perd fluide_.’
It is composed of two sheets of galvanised wrought iron 3 ft. long, 6½
in. wide, and ½ an inch thick, hacked into sharp points in order to
facilitate the discharge of the electricity. He alludes to Callaud’s
basket of coke, but says that its efficiency has not been absolutely
demonstrated. M. Borrel insists upon the _perd fluide_ being immersed in
the water of a well, and one preferably not less than 2 ft. in diameter.
He strongly objects to insulators, and says that he always makes
metallic connection between the gutters, rain-water pipes, &c. and his
conductors. From the surface of the earth to 6 ft. above it, he encloses
his conductor in a wooden case in order that no one may touch it during
a storm.”
* * * * *
We had a long conversation with M. LE COMTE DU MONCEL, of whose remarks
the following is a _précis_:—
He objects to _square_ iron bars because their angles have a tendency to
facilitate lateral discharge.
He objects to conductors being painted, because he believes that the
surface of a conductor acts electro-statically. He knows that the brass
wire rope occasionally used for lighthouses is often destroyed, but
thinks that the theory enunciated in the Report of the Académie des
Sciences, 18th December, 1854 (see Appendix F., p. 62), can hardly be
maintained, and believes it to be more probable that the rope was in a
very bad state of oxidation.
Thinks that conductors should possess _both_ sectional area and surface.
Does not attach much importance to extremely sharp points, but thinks
that the suggestion of one stout central one to receive a disruptive
discharge, surrounded by three or four needles to facilitate silent
discharge, would be good.
The following statement was quoted from the Report of 20th May, 1875
(see Appendix F., page 68), that, “if a conductor cannot be led either
to the subterranean water or to a main water-pipe, no lightning rod
should be erected. It would do more harm than good.” Count du Moncel
said that the paragraph referred chiefly to buildings on large solid
rocks, but that obviously there is every degree of quality in the earth
contact which can be obtained; and that although it is easy to decide at
the two extremes, it is difficult to say how bad the earth must be in
order to render the erection of a conductor inadvisable.
* * * * *
M. JARRIANT, who is the manufacturer employed upon the Municipal
buildings of Paris (and author of two pamphlets, of which abstracts are
given in Appendix F, pages (111) and (115)), accompanied us through his
works, and afforded us all the information which we could desire.
He showed us a large collection of platinum points of various patterns,
ranging in cost from 12s. to 60s. each; he also showed us some which had
been employed by other makers, which were merely hollow sheaths of
platinum filled in with soft metal in order to reduce the cost.
He had also a large variety of upper terminals, including the patterns
used by the City of Paris, by the War Department for its military
establishments, and by civil engineers and architects.
We saw specimens of the ropes, rods, &c., usually supplied. The iron
ropes were galvanized and ¾ in. diameter. The copper ropes were made of
six twisted strands of copper wire enclosing a central core of hemp, the
total diameter being ½ an inch. The iron bars were square galvanized
wrought iron 0·80 in. square, in lengths of 16½ feet, rabbetted at the
ends with two holes for bolts. To make a joint a strip of foil is laid
between the two faces, the bolts are screwed up, and then the whole
joint is very heavily soldered.
Among various works in progress, we saw a highly decorated wrought iron
cross for the roof of a church, which cross would become the summit of
the conductor, its top and the extremity of each arm being furnished
with a short copper terminal tipped with a platinum point.
We were much struck by the fact that in France, where so much attention
has been given to lightning protection, there should be so much
diversity of practice. The Municipality adopt one system, the State
another, the War Department a third, and each individual manufacturer
has, as in England, his hobby.
We desire to record our thanks to Mr. J. Aylmer, C.E., for making the
various arrangements, by which we were able to see so much in the
comparatively short time at our disposal, and also for accompanying us
throughout.
W. H. PREECE.
G. J. SYMONS.
P.S.—A very convenient form of a rough testing apparatus has been made,
by the Silvertown Co., for one of the writers; it consists of one
Leclanché cell, a trembling bell, a key, and a pair of terminals to
attach insulated wires to the top and bottom of the lightning rod, all
fixed in a neat portable mahogany box, and with its aid any one can
readily examine the conductivity of his lightning rod.
APPENDIX L.
ON THE LIGHTNING CONDUCTORS AT THE PARIS INTERNATIONAL ELECTRICAL
EXHIBITION, BY MESSRS. DYMOND AND SYMONS.
It was hoped that at the Paris Electrical Exhibition would be found
examples of the various styles and patterns of lightning rods used in
the several countries of Europe and in the United States, and we
accordingly visited the Exhibition and inspected all the exhibits in any
way relating to the subject.
Those from France were naturally the most numerous (15), but there were
some very elaborate specimens of the system adopted in Belgium, in
accordance with the recommendations of M. Melsens; and there was also
sent by Dr. Weber, of Kiel, a very interesting collection of 12 points
which had been struck by lightning, all more or less fused and damaged.
The French exhibitors showed a great variety of points, but they were
for the most part referable to two or three types or classes, and only
varied in size. The favourite form appeared to be that shown by Fig. 1,
a rather finely tapering brass rod terminated by an acornshaped piece,
from the upper end of which projected a small needle. They were
constructed to be screwed to the top of the iron _tige_. They varied in
size from 1 ft. long and ¾ in. diameter at the base, tapering to ¼ in.
at the acorn, to 2 ft. 6 in. long and 1¼ in. diameter, tapering to ¼ in.
The acorns were generally about twice the diameter of the point to which
they were joined, and were about 1½ diameter long. The needles were
always made of platinum about 1½ in. long and ·1 in. diameter. Some
exhibitors showed a very similar pattern, but made in copper instead of
brass. There were also several specimens of blunt points in copper—the
_Point Municipal_, Fig. 2, tapering from 1 in. to ½ in. diameter and 1
ft. 8 in. long; tapering brass and iron rods, some of them having
platinum cones, were also exhibited. All these points were intended to
be mounted on exceedingly long upper terminals.
The conductors were generally made of wire rope, copper, brass, or
galvanized iron, and in the majority of cases composed of strands of
small wires, though there were a few specimens of ropes made of large
wires (say) ·1 in. in diameter; and there were also some specimens of
conductors made of iron bars with copper expansion bands. These last
specimens were about ·8 in. square, but almost all the ropes seemed to
us too small, generally about ·4 in. diameter, and we were surprised to
see that the iron ropes were no larger than the copper or brass ones.
[Illustration:
4
]
[Illustration:
3
]
[Illustration:
2
]
[Illustration:
1
]
The methods adopted for joining them to the upper terminals were either
to push the end into a socket and pin them across, or more frequently to
tie them more or less loosely round the base.
The practice as to insulation seemed to vary, some makers supplying
insulators and others not, but they almost all provided for carrying the
conductor from 6 to 9 in. away from the face of the building.
There were but few specimens of earth plates, they were in the form of
grapnels, and seemed very inadequate; not one would afford 3 superficial
feet of earth contact.
Some models and drawings showed that the French electricians assumed a
cone of protection whose radius was at least 1·75 of its height. (See
ante page (67).)
Excepting France the most numerous series of exhibits was that from
Belgium, which also contained a complete model of the monument erected
at Lacken in memory of Leopold I., showing the manner in which it had
been fitted with conductors under the superintendence, or according to
the system, of M. Melsens.
The monument referred to is a ten-sided Gothic building, with pinnacles
on two storeys and a spire. On the top of the spire, but below the
figure, is a considerable number of radiating points, and there is a
similar frill round the top of each of twenty pinnacles. Each aigrette
consists of seven copper points, each about 0·4 in. in diameter and 2
ft. long, tapering to a very sharp point; they are all leaded into a
collar or band encircling the stone work; and from them go the rods
about 0·4 in. in diameter, which are first taken into a cast iron box
about 8 in. × 5 in. × 2 in.; into this box are also taken rods which
lead to connections with (1) a well, (2) the water mains, and (3) the
gas mains. When these two series of rods are all in position in the box
it is filled with melted lead, and thus perfect connection is secured.
There were specimens of the aigrette, and also of the manner of joining
the rod to the gas and the water mains, and to the large iron pipe which
is sunk in the well. This is effected by bringing all the rods parallel
with the main, and arranging them, at equal distances from each other,
around it. They are then held tightly to it by two semicircular clamps
bolted together, and melted lead is poured in and caulked. The main, and
probably the inside of the clamps, was filed bright when the joint was
made.
The other exhibits—patterns of points and conductors—do not call for any
special mention, but we may notice that the Belgian makers were
generally much more careful than the French to make good electric
contact at the joints, and some conductors were exhibited cut through
the joints to show the care bestowed in this particular.
From Germany were sent some specimens of wire rope for conductors, made
of the usual strands of small wires. The iron ropes were slightly larger
and of slightly larger wires than the copper, but the former were not
more than 0·6 in. in diameter.
* * * * *
Dr. WEBER, of Kiel, exhibited a collection of 12 points, all which have
been struck by lightning—their length varies from 4 in. to 7 in., they
are of gilded copper, about 1 in. in diameter at the thickest point, and
vary in the acuteness of their extremities—some have platinum needles,
about 0·08 in. diameter, screwed into their points; these needles have,
in most cases, been wholly fused. In some cases the platinum is somewhat
thimble-shaped, and fitted over the copper—in these cases the platinum
is generally wholly melted, and the copper uninjured. Platinum of 0·12
in. diameter has been melted, but there is not one of these points of
which copper of that size has been fused. There is no indication that
these points have been fixed to tiges—on the contrary, they are all
hollow at the base, and have had soldered into them copper ropes, none
exceeding 0·33 in. diameter, and most of them consisting of three
strands of six wires each (=18 wires), the wires being about No. 18
B.W.G.
There were a few specimens of gilded copper points, sent from Austria,
such as Fig. 3; and our English makers also sent a few examples of
points, the crow foot, Fig. 4, for instance, of upper terminals, and of
rope and tape conductors.
E. E. DYMOND.
G. J. SYMONS.
APPENDIX M.
MISCELLANEOUS.
MEANS TO BE ADOPTED FOR ENSURING PERSONAL SAFETY FROM THE EFFECTS OF
LIGHTNING.
(_Abstracted by Prof. G. Carey Foster, F.R.S._)
WORKS CONSULTED:—
│Received from the
_Correspondence_ addressed to Lightning Rod │ Secretary of
Conference. │ Lightning Rod
│ Conference.
Directions for Insuring Personal Safety during │
Storms of Thunder and Lightning; and for * * * │
By _John Leigh_, pp. 60. London (no date). │
_Benjamin Franklin._ Complete Works. 3 vols. 8vo. London, 1806.
_Gehler._ Physikalisches Wörterbuch. Article “_Blitz_,” Leipzig, 1825.
_François Arago._ Meteorological Essays, from the French by Sabine.
London, 1855.
_C. Kuhn._ Handb. d. angewandten Elektricitätslehre. Leipzig, 1866.
The danger to men and animals from the effects of lightning arises from
the fact that the bodies of living animals form comparatively good
conductors of electricity,—better, that is, than rain-water (probably
better even than sea-water), or than trees, walls of brick or stone,
hay-stacks, or in fact than almost any common objects consisting of
non-metallic materials. It may be assumed that the path of a
lightning-discharge striking the earth is determined by the line of
least inductive resistance between the thunder-cloud and the earth.[7]
Hence, a man standing on an open plain, or walking, or riding on
horseback, or in an open vehicle, across it, is liable to be struck by
lightning. There is no evidence that the motion of walking or riding
makes the liability either greater or less than it would be if he were
at rest. The danger is increased, other conditions being the same, by
nearness to water, or to large masses of metal, or other conducting
material, lying flat on the ground or rising only a little way from it.
An umbrella held over-head is probably dangerous, but I do not find
direct evidence that it is so among recorded cases.[8] Such small
metallic articles—money, keys, &c.,—as may be commonly carried in the
pocket, have probably no perceptible effect. In the open country, beyond
the reach of shelter, low-lying positions, if dry, are safer than those
which are more elevated and exposed; but, on the other hand,
water-courses are to be avoided. It is also safer to lie flat on the
ground than to stand or sit. If shelter is within reach, care should be
taken to get _completely under cover_. There is often much more danger
in standing under the lee of a house, or wall, or hay-stack, or thicket
of trees, than in remaining quite exposed. There is but little danger,
however, _inside_ a barn or outhouse, as far as possible from the walls,
or _underneath_ a wagon or the arch of a bridge. The inside of a wood is
also a tolerably safe situation if we keep clear of the branches of the
trees and as far as may be from their trunks. If isolated trees afford
the only shelter within reach, it is advisable to go _near_ them (within
two or three yards of their projecting branches) but not _under_ them.
Leaning against the trunk of an isolated tree during a thunderstorm is
very dangerous. In this case the danger arises from the fact that the
tree is a much better conductor than the air surrounding it, though a
worse conductor than the human body. Hence, if a man stands against a
tree, a line of least inductive resistance is likely to be determined
through his body and continued upwards through the tree. Like
considerations apply in the case of a person standing against a wall, or
other high object, consisting of very imperfectly conducting materials
and unprovided with efficient lightning conductors.
Footnote 7:
The apparently capricious way in which lightning often strikes is not
inconsistent with this statement. It proves, however, that the line of
least inductive resistance is partly determined by atmospheric or
terrestrial conditions which are not perceived by the eye.
Footnote 8:
Is there any evidence to show that soldiers wearing spiked helmets, or
marching with fixed bayonets, are specially liable to be struck by
lightning? Various ancient writers—Cæsar, Seneca, Livy, Pliny, and
others—mention luminous appearances (“Fire of St. Elmo”) presented by
the javelins or pikes of soldiers during thunderstorms at night.
As to people indoors, we need only consider the case of those who are in
buildings which are either not at all or only imperfectly protected by
conductors; for, if a building is thoroughly protected, whatever is
inside it is protected also. Indoors, as out of doors, we have to avoid
forming part of a line of least inductive resistance. This consideration
leads to such rules as the following:—Keep to the lower rooms of a
house, rather than to the upper rooms; also keep as much as possible in
the middle of the room you are in, but avoid being under a metal
chandelier, or a lamp, or other object hung by a metal chain or wire;
keep away from a stove or fire-place, _especially when a fire is
burning_ in it; keep away from large metallic objects which are not in
electrical connection with the ground, especially if they are above the
level of the head (as mirrors, or pictures with gilt frames, hung
against the wall), or below the feet (as an iron pillar or beam
supporting the floor, or an iron staircase leading to a lower storey but
not continued to one above). Franklin recommends “sitting in one chair
and laying the feet up in another,” or as a further precaution “to bring
two or three mattresses or beds into the middle of the room, and,
folding them up double, [to] place the chair upon them.” But best of all
he says is, “where it can be had, a hammock, or swinging bed suspended
by silk cords equally distant from the walls on every side, and from the
ceiling and floor above and below.” Doors and windows are better shut
than open, but it does not seem that this condition is of much
importance.
It may be added for the comfort of the timid that Arago concludes that
the danger of being struck by lightning in a town (Paris) “is less than
the danger of being killed in passing along the street by the fall of a
chimney, or flower-pot, or of a workman engaged upon a roof; this latter
danger being [he imagines] one which occasions very little uneasiness.”
Also it seems to be the universal testimony of those who have been
restored after being struck by lightning that they had not been
conscious of either thunder or lightning. We may accordingly conclude
that all danger from a given discharge is over, not merely by the time
we hear the thunder, but as soon as ever we see the flash.
G. C. F.
INJURY TO GAS AND WATER-PIPES BY LIGHTNING.
The city gas company of Berlin, having expressed the fear that gas-pipes
may be injured by lightning passing down a rod that is connected with
the pipes, Professor Kirchhoff has published the following reply:—
“As the erection of lightning-rods is older than the system of gas and
water-pipes as they now exist in nearly all large cities, we find
scarcely anything in early literature in regard to connecting the earth
end of lightning-rods with these metallic pipes, and in modern times
most manufacturers of lightning-rods, when putting them up, pay no
attention to pipes in or near the building that is to be protected.”
Kirchhoff is of the opinion, supported by the views of a series of
professional authorities, that the frequent recent cases of injury from
lightning to buildings that had been protected for years by their rods,
are due to a neglect of these large masses of metal. The Nicolai Church,
in Griefswald, has been frequently struck by lightning, but was
protected from injury by its rods. In 1876, however, lightning struck
the tower and set it on fire. A few weeks before, the church had had
gas-pipes put in it. No one seems to have thought that the new masses of
metal which had been brought into the church could have any effect on
the course of the lightning, otherwise the lightning-rods would have
been connected with the gas-pipes, or the earth connection been
prolonged to proximity with the pipe. A similar circumstance occurred in
the Nicolai Church in Stralsund. The lightning destroyed the rod in many
places, although it received several strokes in 1856, and conducted them
safely to the earth. Here, too, the cause of injury was in the neglect
of the gas-pipes, which were first laid in the neighbourhood of the
church in 1856, shortly before the lightning struck it. The injury done
to the school-house in Elmshorn, in 1876, and to the St. Lawrence’
Church, at Itzehoe, in 1877, both buildings being provided with rods,
could have been avoided if the rods had been connected with the adjacent
gas-pipes.
“If it were possible,” says Kirchhoff, “to make the earth connection so
large that the resistance which the electric current meets with when it
leaves the metallic conducting surface of the rod to enter the moist
earth, or earth water, would be zero, then it would be unnecessary to
connect the rods with the gas and water-pipes. We are not able, even at
immense expense, to make the earth connections so large as to compete
with the conducting power of metallic gas and water-pipes, the total
length of which is frequently many miles, and the surface in contact
with the moist earth is thousands of square miles. Hence the electric
current prefers for its discharge the extensive net of the system of
pipes to that of the earth connection of the rods, and this alone is the
cause of the lightning leaving its own conductor.”
Regarding the fear that gas and water-pipes could be injured, the author
says: “I know of no case where lightning has destroyed a gas or
water-pipe which was connected with the lightning-rod, but I do know
cases already in which the pipes were destroyed by lightning because
they were not connected with it. In May, 1809, lightning struck the rod
on Count Von Seefeld’s castle, and sprang from it to a small water-pipe,
which was about 80 metres from the end of the rod, and burst it. Another
case happened in Basel, July 9, 1849. In a violent shower one stroke of
lightning followed the rod on a house down into the earth, then jumped
from it to a city water-pipe, a metre distant, made of cast iron. It
destroyed several lengths of pipe, which were packed at the joints with
pitch and hemp. A third case, which was related to me by Professor
Helmholtz, occurred last year in Gratz. Then, too, the lightning left
the rod and sprang over to the city gas-pipes; even a gas explosion is
said to have resulted. In all three cases the rods were not connected
with the pipes. If they had been connected the mechanical effect of
lightning on the metallic pipes would have been null in the first and
third cases, and in the second the damage would have been slight. If the
water-pipes in Basel had been joined with lead instead of pitch, no
mechanical effect could have been produced. The mechanical effect of an
electrical discharge is greatest where the electric fluid springs from
one body to another. The wider this jump the more powerful is the
mechanical effect. The electrical discharge of a thunder cloud upon the
point of a lightning rod may melt or bend it, while the rod itself
remains uninjured. If the conductor, however, is insufficient to receive
and carry off the charge of electricity, it will leap from the conductor
to another body. Where the lightning leaves the conductor its mechanical
effect is again exerted, so that the rod is torn, melted, or bent. So,
too, is that spot of the body on which it leaps. In the examples above
given it was a lead pipe in the first place, a gas-pipe in the last
place, to which the lightning leaped when it left the rod, and which
were destroyed. Such injuries to water and gas-pipes near lightning-rods
must certainly be quite frequent. It would be desirable to bring them to
light, so as to obtain proof that it is more advantageous, both for the
rods and the building which it protects, as well as for the gas and
water-pipes, to have both intimately connected. Finally, I would mention
two cases of lightning striking rods closely united with the gas and
water-pipes. The first happened in Düsseldorf, July 23rd, 1878, on the
new Art Academy; the other August 19th, last year, at Steglitz. In both
cases the lightning-rod, the buildings, and the pipes were
uninjured.”—_Deutschen Bauzeitung._ Quoted in _The Building News_, Sept.
10, 1880.
COLLIERY WORKINGS STRUCK BY LIGHTNING.
THE INSTITUTE OF MINING ENGINEERS.
A meeting of the members of the North of England Institute of Mining and
Mechanical Engineers took place in the Wood Memorial Hall on Saturday,
Mr. G. C. Greenwell in the chair, when the secretary read an account of
an investigation which had been made into a statement that lightning had
entered Tanfield Moor Colliery on the 12th of July last, and traversed
the workings in several directions. Mr. Wm. Joicey kindly gave
permission to examine the witnesses of the occurrence, and the workings
of the colliery, so that a complete and accurate report could be drawn
up of the circumstance; and on the 30th of July, Mr. C. Berkley, Mr. J.
B. Simpson, Mr. W. H. Hedley, and the secretary went out to the
colliery, and were met by Mr. W. Joicey, one of the owners; Mr. Pringle,
the viewer; and Mr. Arkless, the resident viewer. The top of the working
shaft at the colliery is 34 fathoms from the Shield Row seam. An incline
bank leads northwards from the working shaft and ultimately reaches the
day by a drift, and a little to the south is an up-cast shaft. The
engine way leads south from the working shaft, and goes in-bye to a
goaf. Between the goaf and the working shaft are two down-cast shafts.
From what can be gathered the lightning passed down the working shaft
and struck the flat sheets, and then divided itself into two parts, one
of which went north up the incline way and probably passed out to the
day by the drift, where it was supposed to have left traces of its exit
in marks upon a bank near by. The other part went south along the engine
way; but after passing a point where it was noticed its further course
was not known. The thill of the seam is composed of soft sagger, and the
roof of strong post, both of which would offer great obstruction to the
absorption of the electric fluid; and the probability was that this
portion of the fluid had been dissipated in the goaf, or had forced an
exit by way of the down-cast shaft.
The evidence taken was appended.—Joseph Kirtley, back-overman, said a
light, distinct but not very bright, fell and struck the flat sheets,
and split up into several lights like a lot of lighted matches. He could
only see the light for a moment among the tub wheels. It struck the
puller-out, Wm. Watson, on the arm, and he complained that his arm was
numb, and when he got home it was yellow from the wrist to the elbow. A
heavy peal of thunder was heard very distinctly almost at the same
moment. No injury was done either in the shaft or on the road where the
lightning was said to have passed. He could liken it to nothing better
than a box of matches all struck at once.—James Offord, onsetter, said
he heard a crack like the report of a small pistol, and saw a light
close to his feet.—William Watson, puller-out at the bottom of the pit,
said he saw a flash of light come down and heard a noise like a gun: it
struck on the plate or flat sheet. He saw the light divide when it
struck. The light when it struck was very bright, but did not brighten
up the place to any distance.—Thomas Chrisp, a deputy, said he saw
something like a lot of fire flying, and thought the tram had cut the
point. It was as though a person had trodden upon matches and they had
gone off. The fire seemed a little larger than the light of a candle,
and to the best of his judgment came along the metals.—John Greener saw
a light on the rail about the size of a candle flickering, not steady.
It appeared to travel along the rail, and as it passed the tram made a
noise like the crack of a pistol, and he thought it was matches or
something on the way that was cracking.—John Hagan, a putter, said he
saw the lightning come along the plates. It caught him as it passed and
gave him a queer feeling in the legs. It made a sharp, cracking noise in
the plates like a gun.—George Chrisp, a siding minder, said he was about
50 yards from the shaft, and heard a cracking noise, and saw a bright
light and flash of fire against the big winding sheave, two feet
diameter, like five or six matches going off at once. There were no tubs
running by at the time.—Matthew Hardy, an engine flatter, who was about
100 yards along the shaft siding, said he saw a light like a spark from
a lamp, and there was a noise like a match being struck by a tub passing
over it. The light appeared to be close to him on the rope, which was
running.—It further appeared that the rails were fished; that it was not
noticed whether the lightning came down the rails or the rope; that it
was a self-acting incline; that a noise as of a pistol or gun shot was
heard when the light came to the tram; that a similar noise was heard as
the light left the tram; and that the metallic contact might have been
broken here by a fish-plate being off. The gentlemen who conducted the
inquiry had every reason to believe that the information thus obtained
forms a valuable record of the occurrence, and places beyond doubt the
possibility of lightning penetrating into the workings of collieries.—In
the course of the discussion which followed the reading of the paper,
Mr. A. L. Stevenson mentioned the occurrence of a similar circumstance
at Page Bank, about 10 years ago.—Professor Herschell said that in order
to produce an explosion the electric fluid must come in contact with a
highly explosive mixture; and the occurrence in question showed the
desirability of lightning conductors at collieries, and of the subject
being investigated by mining and electrical engineers.—Cordial votes of
thanks were given to the authors of the papers.—_Newcastle Daily
Journal._ October 5th, 1880.
ACCIDENTS BY LIGHTNING AT THE SWAN COTTON MILL, CHADDERTON, OLDHAM.
REPORT BY J. DOHERTY, A.S.T.E.
[On July 13th, 1880, during a thunderstorm, the large 400 light gas
meter of this mill, though locked up in a cellar, and with no light
near it, exploded, and the gas, which is supplied through a 4–inch
main, was ignited. This was repaired, but on July 5th, 1881, during
another thunderstorm, precisely the same accident occurred. At the
request of Mr. Preece, F.R.S., Mr. Doherty, of H. M. Postal
Telegraph Service, went and inspected the works, and forwarded the
following report.—ED.]
_21st July, 1881._
A very careful investigation of the Swan Mill premises has been
made, with a view of arriving at some explanation of the recent
injury to the gas meter, which was undoubtedly caused by lightning.
The building is a large one, having for its internal supports a
number of cast iron columns running from floor to basement, and on
the top of the building, I am told, there are numerous iron gutters;
round the various rooms are carried large iron gas pipes, and in
numerous instances this gas piping is dead against the iron caps of
the columns, thus the lightning may have struck any portion of the
building, and the current have been conveyed, safely, by the gas
piping to the large gas meter, where an imperfect joint
(electrically imperfect) existed, viz., an india-rubber ring placed
between the faces of the iron joint. It is to be regretted that the
connecting pipes were not on the premises at the time of my visit,
otherwise I could have spoken with a greater degree of certainty,
but I have not the slightest doubt in my own mind as to the
insulating ring between the joints being the cause of rupture.
Tests were made, showing that the continuity of the present pipe is
lessened by the existence of another india-rubber ring, and the
oxidation of the connecting screws at another joint.
I advised the Directors of the Spinning Company to connect the
outlet and inlet main pipes by iron or copper wire straps. I feel
convinced that if this had been done prior to 5th July the accident
would not have occurred.
J. DOHERTY.
ESSAY ON THE EFFECTS OF HEAVY DISCHARGES OF ATMOSPHERIC ELECTRICITY, AS
EXEMPLIFIED IN THE STORMS OF THE SUMMER OF 1846 * * * * AND REMARKS ON
THE USE AND APPLICATION OF LIGHTNING CONDUCTORS. BY E. HIGHTON, ESQ.,
C.E.
(Transactions of the Society of Arts for 1846–47. London. Sm. 4to).
(_Abstracted by G. J. Symons, F.R.S._)
The author’s primary object in studying the subject was the discovery of
a method of protecting telegraphic apparatus from injury and danger.
That has long been accomplished, but some remarks in the Paper seem
worthy of extraction.