Lower coast gazette., 1909-07-17
Essentials in Lightning Rod Con-
EtrtfCtiOn.

This statement OF what Is absolutely
necessary in 2 rod to furnish protec-
ton against any ordinary thunderbo!t,
has been asked of the State Fire Mar
shals' Association of America by farm
mutual insurance companies who have
determined to increase the assessment
or lessen the amount paid, urunrocded
buildings in case of loss by lightning.
Fortunately, nearly every rod now Of
fered, if installed as indicated below,
will fill the requirements.
In France the lightest steel rod per
mitted is three-tfths of an inch square.
A rod of copper must weigh, according
to the scientists of Germany, as much
as a solid copper wire, one-third of an
inch in diameter,
1t mush be run from permanently
moist earth up to and along the comb
of the building and down to perma-
nently moist earth.
A section Of rod, securely held erect,
must rise from the circuit, a height Of
five feet every twenty feet along the
roof comb and there must be one ris-
ing above and close beside each chin
ney, or other prominence.
On each upright section must be one
or more tips of a metal that will stay
bright.
The rod must be held away from the
building not nailed to it.
To disregard any n of these
''musts' is to seriously impair the
value of the rod. A rod that in any
way fell short of these requirements
would not be worth putting up.
THE BEST shape.
The metal in a rod shoeld be shaped
so as to give it a large surface because
the current caused by a thunderbolt is
! the sort that travels near the surface
of a conductor. That is called "skin
effect" for the electricity crowds into
the one-thirtieth of an inch next to the
external surface. Many lightning rod
agents believe and teach that electric
ity travels on the outside Of a wire. 1t
certainly cannot.
A steel rod is rolled in a star shape
and galvanized. Another rod is made
by rolling sheet copper over star shaped
steel. This gives a copper surface and
a metal core to take up heat into which
the energy of the flash is converted.
All other copper rods are made OF
many wires in order that they may
have a large surface. The way in
which the wires in copper cables are
twisted or woven does not affect their
capacity for taking care of lightning
strokes.
An ideal rod, so far as conduction is
concerned, would be one in tape form
but it would be inconvenient and liable
to accident.
BURYING THE END.
Cloud electricity forces its way
through the air to reach the under
ground water which feeds our wells. A
rod is worthless if not run down to
where there is permanent moisture. In
most localities this depth is eight to
ten feet. In rodding an expensive
building it is desirable, but rot necess-
airy to attach a a Of metal to the
end of the rod.
A section Of rod must rise we'll above
each chimney for the moisture in smoke
weakens the resistance of the air to
electricity. The kitchen chimney,
above all others, should be protected
for it is the one most used in the thun.
der storm season.
There is no we'll established rule ir
regard to connecting cutters, saddles,
l rain spouts and other. metal on a build
ing to the rod by wires. When q roc
is struck there are oscillations ane
surgings of electricity in its neighbor
hood, 50 a spark may be given off b!
any metal near by. If a rod runs with
in a few inches of any metal that i
l not grounded the practice is to connec
them. Gas pipes should not be con
nected to the rod.
THE POINTS.
: The greater the number of points tn
greater the silent discharge from tn
rod to avert a stroke, and the create
4 the gathering power of the rod Of
stroke does come. Therefore to U.s.
e clusters of points is wise.
The fact that many of the long slen
e der points are melted when struck
d shows that they should be made thicke
at the expense of length.
Glass insulators hold a rod we'll bu
8 electricity does not leave metal to ru
g on siding or shingles even when the
n are rain wet.
e Before sawmills had removed the ia
timbers. lightning struck trees rattle
than houses. A tree trunk is a bundl
e of pipes full Of water which is n Q
y the best conductors, and trees tina
grow tall have a tap root reaching t
l. permanently moist ground. Becaus
ID wood is not q good conductor, a tree
often torn asunder by part Of tn
ID energy of the thunderbolt being co,
verted into heat, which changes tn
water in IL In steam 50 suddenly thu