Year: 1874

and it always takes place before dis
charge. Now it has been discovered that
when electricity is accumulated in body
in this manner, it can most readily es-
cape by sharp points because in them It
meets with the least resistance A lighted
candle held near the prime conductor Of
an electrical machine furnished with a
point will be nearly blown out by the
current of air produced by the escape of
the electricity. Lightning rods are there
fore provided with sharp points to allow the
accumulated negative fluid to pass off
readily into the air and neutralize the
positive fluid of the thunder cloud.


The object being to make so good
passage for the lightning to the ground as
to remove all danger of its leaping to some
conductor in the house, the greatest care
must be taken not to have any break in
the conductivity. As it is inconvenient to
manufacture or transport the rods in one
piece, the different parts must be in
intimate connection when they are put up;
it is best to have them soldered and the
joints protected from the air and moisture


The point of the rod should be extended
a little above the chimney or highest part
Of the building, and should be fastened in
contact with the building by staples or
cleats. Glass insulators should not be
employed, IL makes no difference in
conductivity whether the rod is painted or
not painted.


No building can be said to be properly
rodded or protected against lightning,
unless the lower part Of the rod or terminal


under the ground is made quite extensive,
The extremity Of the rod should connect


with masses Of good conducting materials,
such rs old iron, or iron ore, or coke, or
charcoal, laid In trenches, or the rod itself
should be elongated, sunk deep In the
ground, aud carried considerable distance
from the building, and put in connection
with water or moist earth if possible
The golden rule for safety is:-"Provide
the largest possible area of conducting
surface for the terminal Of the rod"


A lightning rod which Is not properly

connected with the earth is quite danger
Gus. The very common method Of merely
sticking the lower end Of the rod down
into the dry earth near the surface of the
ground is bad, and endangers the building,
because dry earth is such poor conductor,
and the amount of rod surface in contact
with the earth is so small. Under such
conditions, portion Of the electric cur
rent will be likely to find an easier path to
the earth, through the building than thro
the rod and part of the electricity will
therefore leave the rod, strike into the build
ing, and down in various directions into tho
earth, making havoc as itgoes. As measure
ofprudence, house owners should look 10 die
terminals Of their lightning rods, and place
there considerable amount of the con-
Quoting materials above named.


BY adopting this simple expedient, many
buildings, otherwise unsafe, will be rem
dered comparatively secure from damage
by lightning.


As an electrical conductor, well burnt
charcoal ranks next to the metals. Me-
tallic ores come next to charcoal Water
and moist earth, which are so frequently
recommended as terminals for lightning
rods, are among the poorest of conductors.


One of the best protected buildings that
we have heard of is that Of Mr.. John Knox
Smith, an intelligent English merchant
residing at Singapore. His country house
is built on prominence, upon a bed of
iron ore, with which the house lightning
rods are made to communicate. The lower
ends of the rods thus have very exten-
siye conducting surface, and the protection
afforded is considered perfect. Thunder
storms and lightning strokes are very fire.
quent, but the house has never been in
jured


1t was supposed to have been establish
ed by Charles and Gay Lussac that a light
ming rod protected an area whose radius
was double the hight Of the rod extending
above the building, but this rule is no
longer reliable by reason of the extensive
use Of metals in the shape of pipes, ect., in
the construction of the buildings Of our
day.


When electricity finds several paths TO
The ground, it will prefer the best, it is
true; but some portion viii also pass along
The poorer conductors. II, therefore, any
metallic substances lie within the area
to be protected, they are in dan
ger Of being struck, This is especially
rue where the lightning has chance to
Jump to the gas and water pipes of build
ing. II is good plan to connect these
pipes with the lightning rod; if the rod is
struck, the electricity win then have an
excellent path into the ground and will be
'apidly diffused over the vast underground
network Of pipes, The danger to the in
mates Of the house Of being struck from
Ihese pipes is less than that Of receiving n |
'hOck from the powerful induced currents,
liable to be developed in them, If uncon-
,ectcd, during a thunderstorm.


The more rods on building the better,
specially if all are connected with each
'ther pear their upper ends.


Multiple lightning conductors arc use
dl because zach one helps the other, and
I the discharge is too great for one, they
viii be able to carry il between them. hut |